This document provides an overview of anaerobic digestion and biogas production. It discusses the types and settings of digesters, as well as digester tank design, digestate management, gas upgrading and handling, gas use, project development, construction methodology, and examples of US projects. The document covers the chemistry and process of anaerobic digestion, which involves the breakdown of organic matter by microbes in oxygen-free conditions to produce biogas and digestate. It also addresses gas yield modeling and factors that influence biogas production rates.
1) The document describes a study on optimizing an anaerobic reactor for treating wastewater from a dairy industry. 2) Two types of reactors were tested - one with a fixed film media and one with a floating film media. 3) The fixed film media reactor achieved 87-91% COD removal, while the floating film media reactor achieved 84-86% removal as the hydraulic retention time was increased from 5.3 to 5.9 m3/day over 4 weeks.
This document summarizes a project to produce biohydrogen gas from peach waste using the bacterium Thermotoga neapolitana. Musser Farm produces over 60,000 kg of peach waste annually that is currently disposed of in waste ponds. The goals of the project are to design a process to use all the peach waste to produce biohydrogen gas via bacterial fermentation, capture the gas for energy use, and find beneficial uses for the remaining effluent. Two reactor designs are considered: a batch reactor and continuously stirred tank reactor (CSTR). Economic and sustainability analyses indicate the CSTR design would be most viable, producing an estimated 132 kg of hydrogen gas annually at a profit of $2,520 per year.
The document summarizes the fields of expertise and industrial targets of the Centre des Technologies Agronomiques (CTA). The CTA specializes in (1) innovative anaerobic filter digesters that produce biogas more efficiently, (2) recovering thermal energy from digestion to heat greenhouses, and (3) irrigating crops with residual waters. Industrially, the CTA offers feasibility studies, digester design, and demonstration projects. The document then provides details on the methanization process, different biogas production systems, solid-liquid separation, the CTA's anaerobic filter system, a new farm setup using digestion, and the CTA's laboratory services.
IRJET - Mono and Co-Digestion of Laminaria Digitata with Simulated Food W...IRJET Journal
This study examined anaerobic digestion of the seaweed Laminaria digitata both on its own (mono-digestion) and combined with simulated food waste (co-digestion) in continuous reactor experiments. Different mix ratios of L. digitata and food waste were tested in continuous stirred tank reactors over 85 days. The optimal mix ratio for highest methane production and efficiency was found to be 90% L. digitata and 10% food waste. Mono-digestion of L. digitata led to reactor failure due to accumulation of volatile fatty acids and lowered pH as organic loading rate increased. Co-digestion helped dilute inhibitory components and improved digestion stability compared to mono-digestion of L. digitata alone.
Waste to Watts: Anaerobic Digestion of Livestock Manure (Sood)Iwl Pcu
By: Dave Sood, Consultant, The presentation will cover key aspects of anaerobic digestion:
-Methane Production from Manure
-AD and Its Benefits
-AD Process
-Operating Conditions for AD
-Manure Characteristics and Digester Types
-AD and Water Quality
-Manure Characteristics and Digester Types
-Economic Analysis
-AD in Europe
-Why Digesters Fail?
-Cold Climate Digesters
-Key to Successful Digesters in Cold Climates
-A success story & Carbon Credits: Haubenschild Dairy, Minnesota, USA
The document summarizes an experimental study that compared the methane generation potential from brewery wastewater and domestic wastewater using an upflow anaerobic sludge blanket (UASB) reactor. The study involved setting up two experimental systems - one with brewery wastewater and one with domestic wastewater. Various parameters like COD, pH, methane production were monitored over a 15 day period. The results showed that the brewery wastewater had higher COD removal efficiency and methane production compared to the domestic wastewater. The study provides useful insights into evaluating the energy recovery potential from different wastewater sources using anaerobic digestion.
This document summarizes a student's research project on treating whey wastewater from a dairy company using anaerobic, aerobic, and anoxic treatment systems. The student characterized the whey wastewater, conducted treatment in anaerobic, aerobic, and anoxic reactors, and analyzed various parameters such as COD, TOC, TN, and TP before and after each treatment. The highest COD, TOC, TN, and TP removals were achieved in the aerobic reactor, followed by anoxic and then anaerobic reactors. The student concluded that an anaerobic-anoxic-aerobic treatment combination provides better results for whey wastewater treatment compared to
The activated sludge process treats wastewater by aerating it in a basin containing microorganisms that metabolize and remove organic matter. Part of the organic matter is converted to new biomass cells while the rest is oxidized. The new cells are separated from the treated water as sludge in settling tanks. Some of the sludge is returned to the aeration basin while the rest is removed as waste sludge. The document discusses factors such as mixing mechanisms, hydraulic retention time, organic loading rate, sludge retention time, oxygen requirements, and sludge recycling that influence the design of activated sludge systems.
1) The document describes a study on optimizing an anaerobic reactor for treating wastewater from a dairy industry. 2) Two types of reactors were tested - one with a fixed film media and one with a floating film media. 3) The fixed film media reactor achieved 87-91% COD removal, while the floating film media reactor achieved 84-86% removal as the hydraulic retention time was increased from 5.3 to 5.9 m3/day over 4 weeks.
This document summarizes a project to produce biohydrogen gas from peach waste using the bacterium Thermotoga neapolitana. Musser Farm produces over 60,000 kg of peach waste annually that is currently disposed of in waste ponds. The goals of the project are to design a process to use all the peach waste to produce biohydrogen gas via bacterial fermentation, capture the gas for energy use, and find beneficial uses for the remaining effluent. Two reactor designs are considered: a batch reactor and continuously stirred tank reactor (CSTR). Economic and sustainability analyses indicate the CSTR design would be most viable, producing an estimated 132 kg of hydrogen gas annually at a profit of $2,520 per year.
The document summarizes the fields of expertise and industrial targets of the Centre des Technologies Agronomiques (CTA). The CTA specializes in (1) innovative anaerobic filter digesters that produce biogas more efficiently, (2) recovering thermal energy from digestion to heat greenhouses, and (3) irrigating crops with residual waters. Industrially, the CTA offers feasibility studies, digester design, and demonstration projects. The document then provides details on the methanization process, different biogas production systems, solid-liquid separation, the CTA's anaerobic filter system, a new farm setup using digestion, and the CTA's laboratory services.
IRJET - Mono and Co-Digestion of Laminaria Digitata with Simulated Food W...IRJET Journal
This study examined anaerobic digestion of the seaweed Laminaria digitata both on its own (mono-digestion) and combined with simulated food waste (co-digestion) in continuous reactor experiments. Different mix ratios of L. digitata and food waste were tested in continuous stirred tank reactors over 85 days. The optimal mix ratio for highest methane production and efficiency was found to be 90% L. digitata and 10% food waste. Mono-digestion of L. digitata led to reactor failure due to accumulation of volatile fatty acids and lowered pH as organic loading rate increased. Co-digestion helped dilute inhibitory components and improved digestion stability compared to mono-digestion of L. digitata alone.
Waste to Watts: Anaerobic Digestion of Livestock Manure (Sood)Iwl Pcu
By: Dave Sood, Consultant, The presentation will cover key aspects of anaerobic digestion:
-Methane Production from Manure
-AD and Its Benefits
-AD Process
-Operating Conditions for AD
-Manure Characteristics and Digester Types
-AD and Water Quality
-Manure Characteristics and Digester Types
-Economic Analysis
-AD in Europe
-Why Digesters Fail?
-Cold Climate Digesters
-Key to Successful Digesters in Cold Climates
-A success story & Carbon Credits: Haubenschild Dairy, Minnesota, USA
The document summarizes an experimental study that compared the methane generation potential from brewery wastewater and domestic wastewater using an upflow anaerobic sludge blanket (UASB) reactor. The study involved setting up two experimental systems - one with brewery wastewater and one with domestic wastewater. Various parameters like COD, pH, methane production were monitored over a 15 day period. The results showed that the brewery wastewater had higher COD removal efficiency and methane production compared to the domestic wastewater. The study provides useful insights into evaluating the energy recovery potential from different wastewater sources using anaerobic digestion.
This document summarizes a student's research project on treating whey wastewater from a dairy company using anaerobic, aerobic, and anoxic treatment systems. The student characterized the whey wastewater, conducted treatment in anaerobic, aerobic, and anoxic reactors, and analyzed various parameters such as COD, TOC, TN, and TP before and after each treatment. The highest COD, TOC, TN, and TP removals were achieved in the aerobic reactor, followed by anoxic and then anaerobic reactors. The student concluded that an anaerobic-anoxic-aerobic treatment combination provides better results for whey wastewater treatment compared to
The activated sludge process treats wastewater by aerating it in a basin containing microorganisms that metabolize and remove organic matter. Part of the organic matter is converted to new biomass cells while the rest is oxidized. The new cells are separated from the treated water as sludge in settling tanks. Some of the sludge is returned to the aeration basin while the rest is removed as waste sludge. The document discusses factors such as mixing mechanisms, hydraulic retention time, organic loading rate, sludge retention time, oxygen requirements, and sludge recycling that influence the design of activated sludge systems.
The document discusses various aspects of anaerobic digestion and aerobic treatment systems. It provides details on:
- The multi-step anaerobic digestion process where bacteria break down biodegradable material in the absence of oxygen.
- Configurations for anaerobic digesters including batch vs continuous systems, mesophilic vs thermophilic temperatures, and single-stage vs multi-stage complexity.
- Aerobic treatment systems that use aerobic bacteria to further treat sewage after an initial anaerobic septic tank process.
- Types of aerated lagoons or basins used to promote biological oxidation of wastewaters, including suspension mixed and facultative lagoons with different
Professor Sandra Esteves of the Wales Centre of Excellence for Anaerobic Digestion discusses producing chemicals and biopolymers from wastes and biomass through anaerobic digestion and fermentation processes. Specifically, she outlines research on producing organic acids like acetic acid and urea from methane, volatile fatty acids from food and sewage wastes, and polyhydroxyalkanoates (PHAs) as bioplastics from fermentation of volatile fatty acids using Cupriavidus necator bacteria. Real-time monitoring and factors like volatile fatty acid feeding rates, nutrient sources, and sodium chloride levels are investigated to optimize PHA production.
This document summarizes research on the hydrothermal liquefaction of algae feedstocks in a continuous-flow reactor system. Key points:
- Algae can be converted to an upgradeable biocrude through hydrothermal liquefaction at 350°C and 20 MPa in a continuous-flow reactor, without the need for solvents. High carbon conversions were achieved even at high algae concentrations.
- Catalytic hydrotreating was effectively used to upgrade the biocrude through hydrodeoxygenation, hydrodenitrogenation, and hydrodesulfurization, producing hydrocarbon fuels.
- Catalytic hydrothermal gasification of the aqueous byproduct stream effectively produced fuel gas and allowed for
The document discusses various aspects of anaerobic wastewater treatment processes. It provides information on the types and characteristics of anaerobic reactors including UASB and EGSB reactors. It also describes the formation of anaerobic granular sludge, which allows high biomass retention and efficient COD removal. Additionally, it compares the kinetics, environmental factors, and advantages of anaerobic versus aerobic wastewater treatment processes.
This document discusses a study on fermenting centipede grass into silage. The objectives were to determine how much acid was produced by bacteria and how much substrate was consumed under anaerobic conditions. Two reactors were used, one with added sucrose and one without. Methods included measuring pH, acidity through titration, and COD over several days. Models were created to simulate biomass formation and product formation in each reactor. Results showed pH increased over time while acid production decreased. COD readings did not follow a clear trend. The added sugar reactor showed higher predicted acid and biomass yields. Limitations may have included paint can contamination and opening reactors for testing.
The document provides an overview of anaerobic digestion, which is a natural process where microorganisms break down organic materials in an oxygen-free environment, producing biogas. It discusses the history of anaerobic digestion from its discovery in the 1600s to current applications. The document also outlines the multi-step digestion process and different technologies used, including liquid, high solids, plug flow, micro, and high rate digestion as well as co-digestion.
This document discusses the design of a system to produce vinegar from excess or damaged peaches. It proposes a two-step fermentation process using yeast to convert sugar to ethanol and then Acetobacter aceti to convert the ethanol to acetic acid. The design includes washing, crushing, and pressing peaches followed by serial fermentation reactors and filtration to produce the vinegar. Byproducts like pomace and carbon dioxide would be sold or composted to increase sustainability. The annual yield is estimated to be 20,059 kg of vinegar per year which could be sold for $1.80 per 32 oz bottle to offset the $21 million startup and $5.8 million annual operating costs.
This document describes a project to design an energy-producing waste treatment system using anaerobic co-digestion of organic wastes from the University of Arkansas Swine and Poultry Units coupled with algae cultivation. A prototype was constructed and tested to generate data for designing a full-scale system. The full-scale system was designed to treat all biological wastes from the units while producing net energy and retaining nutrients that could be used as fertilizer.
Development of a Laboratory Scale Biodiesel Batch ReactorIRJET Journal
The document describes the development of a laboratory-scale batch reactor for biodiesel production. Researchers in Nigeria designed and built a 12-liter reactor using locally available materials to make biodiesel production more accessible. Experiments using the reactor showed that the maximum biodiesel yield was obtained after 20 minutes, and the properties of the biodiesel matched standards. The reactor design incorporated a helical agitator and integrated separation unit to efficiently produce biodiesel from waste vegetable oil on a small scale.
Biogas Production Enhancement from Mixed Animal Wastes at Mesophilic Anaerobi...IJERA Editor
In this work, the effect of mixing ratio of cattle dung (CD) and poultry droppings (PD) on biogas generation was
determined. Mixtures of various CD: PD ratios (100% : 0%; 50% : 50%; 60% : 40%; 80% : 20% and 0% :
100%) were prepared, analyzed and then aerobically digested for a period of 40 days. For each mixture,
fermentation was carried out in a 20 L capacity digester. Results showed that biogas was obtained from the
digestion of CD and PD alone, showing the biogas from CD was several times larger than that from PD.
Furthermore, the resulted biogas yields from mixtures were found a function of the CD : PD ratio, the yield from
the ratio 80 : 20 was the maximum. Biogas yields from the prepared mixtures were found and arranged from
larger to lower in the form of (CD : PD) ratios as follow: 80% : 20%; 100% : 0.0%; 60% : 40%; 0.0% :
100%;50% : 50%. Addition of CD to PD enhances the PD production of biogas, while addition of a small
portion of PD to CD gave the maximum yield, a result not determined in literature. In other hand, larger
additions of PD to CD reduced the biogas yield. The effect of pH was also determined and found better around
7.0. These results are in agreement with research work in literature.
This document presents a comparative study of the performance of activated sludge processes in a bubble column reactor and compact jet loop reactor. Experiments were conducted using synthetic wastewater in laboratory scale models of each reactor type. The chemical oxygen demand (COD) removal efficiency was measured at different mixed liquor volatile suspended solids (MLVSS) concentrations and hydraulic retention times. The results showed that a COD removal efficiency of over 85% could be achieved in the bubble column reactor, and over 95% in the compact jet loop reactor, when operated at an MLVSS of 3000 mg/L and aeration time of 1 hour. The compact jet loop reactor demonstrated better COD reduction performance than the bubble column reactor under the conditions tested.
The document summarizes a seminar presentation on anaerobic digestion of whey waste. The presentation covers: (1) Introduction to anaerobic digestion and characteristics of whey waste; (2) Aims to determine waste reduction, methane yield, and analyze digested sludge; (3) Justification that whey is a pollutant and disposal is costly so it should be treated; (4) Methods which will involve setting up a lab-scale anaerobic digester to produce biogas and analyze methane production.
Dr. Marty Matlock - Lifecycle Assessment of Aquaculture and Aquaponics System...John Blue
Lifecycle Assessment of Aquaculture and Aquaponics Systems in Hawaii and How They Can Improve your Operation - Dr. Marty Matlock, Center for Agricultural and Rural Sustainability, University of Arkansas, from the 2017 NIAA Annual Conference, U.S. Animal Agriculture's Future Role In World Food Production - Obstacles & Opportunities, April 4 - 6, Columbus, OH, USA.
More presentations at http://www.trufflemedia.com/agmedia/conference/2017_niaa_us_animal_ag_future_role_world_food_production
Utilization of pre aerated sludge in activated sludge processeSAT Journals
Abstract The research was carried out with Pre aerated Sludge in Activated Sludge Process to observe the effect of Pre-aerated Sludge on BOD, COD , Phosphate, Nitrate, MLVSS mainly in treatment of dairy wastewater. The experimental process involves the conventional Activated Sludge Process (ASP) in which microorganisms are kept in suspension by mixing and aerating the wastewater. The study is to be conducted by following two methods: 1) utilizing non pre-aerated sludge and 2) utilizing pre-aerated sludge. In the first method the dairy wastewater measuring five liters and 400 ml of non-pre-aerated sludge is filled in the aeration tank and was aerated in the aeration tank where air (or oxygen) was supplied for regular intervals of 30, 60, 90, 120 minutes respectively and samples are collected before aeration and at regular intervals. In the second method the dairy wastewater measuring five liters and 400 ml of pre aerated sludge (with 20, 40 and 60 minutes pre-aeration) are filled in aeration tank. This tank is aerated for regular intervals of 30, 60, 90, 120 minutes respectively. The samples are collected before aeration and at regular time intervals. The sludge is to be not recycled to the aeration tank. Testing of different parameters like BOD, COD, Phosphate, Nitrate and Mixed liquor volatile suspended solids was carried out on the samples aerated with different aeration time, with and without pre-aerated sludge and consequent results are to be found. By utilization of pre-aerated sludge, the concentrations of various parameters to be considered for study are to be found decreased when compared with the values of concentration without using pre-aerated sludge. It will be very clear that removal of various parameters from wastewater is effective up to the optimum period for pre-aeration beyond this period removal of various parameters from wastewater will not be effective. Keywords: Activated Sludge Process, BOD, COD, Phosphate, Nitrate, MLVSS.
The document discusses biofuels, including their need, benefits, and analysis. It provides an introduction to biofuels and their role in reducing carbon emissions. It then discusses the need for biofuels in terms of their ease of use in vehicles, ability to provide energy security, potential for economic development, and ability to reduce greenhouse gas emissions. However, biofuels also face objections regarding their economic viability and environmental impacts. The document concludes by discussing life cycle analysis of biofuels and perspectives on biodiesel.
Dr. Greg Thoma - An Overview of Aquaculture through the lens of Environmental...John Blue
An Overview of Aquaculture through the lens of Environmental Sustainability - Dr. Greg Thoma, University of Arkansas, College of Engineering, from the 2018 NIAA Annual Conference, Livestock Traceability: Opportunities for Animal Agriculture, plus the Traceability and the Real World Interactive Workshop, April 10 - 12, Denver, CO, USA.
More presentations at https://www.youtube.com/channel/UCeUDeS810OcOfuEYwj1oHKQ
This document summarizes the results of a life cycle assessment (LCA) comparing bioplastic containers to petroleum-based containers. The LCA analyzed the environmental impacts from cradle-to-gate and partial cradle-to-grave. For the cradle-to-gate analysis, bioplastics made from PLA, PHA, and various biocomposite formulations were compared to polypropylene containers. The LCA found that the bioplastics generally had higher global warming and fossil fuel impacts than polypropylene, though some formulations like PLA-SPA-BioRes performed better. A partial cradle-to-grave analysis considered various end-of-life scenarios for the containers.
Anaerobic Digestion: Co-Digestion and Operational Issues LPE Learning Center
Proceedings available at: http://www.extension.org/67744
A study was conducted to assess the performance of various mixing regimes on methanogen biomass content in anaerobic digesters. Methane production in anaerobic digesters is directly related to the methanogens within the system. Current systems involve mixing to increase biogas production and system efficiency, however little is known about the underlying mechanisms of this relationship. In this study three pilot scale anaerobic digestion systems with three different mixing regimes were run with replication to examine the impacts to methanogen biomass content and biogas production. The results will provide insight for operational recommendations as well as the basic microbial processes with digestion systems which are critical for optimization.
This document presents information on upflow anaerobic sludge blanket (UASB) reactors. It discusses that the UASB technology was developed in the 1970s to treat industrial and sewage wastewater using anaerobic digestion. The key factors affecting UASB reactor performance are identified as organic loading rate, nutrients, hydraulic retention time, volatile fatty acids, operational temperature, and operational pH. Advantages of UASB reactors include high efficiency, simplicity, flexibility, low space and energy requirements, and low sludge production, while disadvantages include low pathogen/nutrient removal, long start-up times, potential for odors, and need for post-treatment.
Algal biomass can be used to produce biogas through anaerobic digestion, providing a renewable source of energy. The biogas production process involves four key stages - hydrolysis, acidogenesis, acetogenesis, and methanogenesis - where bacteria break down the algal biomass into methane gas. The end products include biogas, digestate fertilizer, and water, providing alternatives to fossil fuels and chemical fertilizers while reducing greenhouse gas emissions.
Methane and power produced from anaerobic digestion of algae can be used to generate electricity and reduce greenhouse gas emissions. Algae grow quickly and absorb carbon dioxide, so the carbon released from burning the biogas was recently absorbed by the algae and is part of a carbon-neutral cycle. Anaerobic digestion of algae involves breaking down the algae into biogas in an oxygen-free tank, then collecting and using the methane gas. The remaining digestate has applications as fertilizer. Overall, algal production for biogas is a sustainable process that generates renewable energy while recycling carbon dioxide.
The document discusses various aspects of anaerobic digestion and aerobic treatment systems. It provides details on:
- The multi-step anaerobic digestion process where bacteria break down biodegradable material in the absence of oxygen.
- Configurations for anaerobic digesters including batch vs continuous systems, mesophilic vs thermophilic temperatures, and single-stage vs multi-stage complexity.
- Aerobic treatment systems that use aerobic bacteria to further treat sewage after an initial anaerobic septic tank process.
- Types of aerated lagoons or basins used to promote biological oxidation of wastewaters, including suspension mixed and facultative lagoons with different
Professor Sandra Esteves of the Wales Centre of Excellence for Anaerobic Digestion discusses producing chemicals and biopolymers from wastes and biomass through anaerobic digestion and fermentation processes. Specifically, she outlines research on producing organic acids like acetic acid and urea from methane, volatile fatty acids from food and sewage wastes, and polyhydroxyalkanoates (PHAs) as bioplastics from fermentation of volatile fatty acids using Cupriavidus necator bacteria. Real-time monitoring and factors like volatile fatty acid feeding rates, nutrient sources, and sodium chloride levels are investigated to optimize PHA production.
This document summarizes research on the hydrothermal liquefaction of algae feedstocks in a continuous-flow reactor system. Key points:
- Algae can be converted to an upgradeable biocrude through hydrothermal liquefaction at 350°C and 20 MPa in a continuous-flow reactor, without the need for solvents. High carbon conversions were achieved even at high algae concentrations.
- Catalytic hydrotreating was effectively used to upgrade the biocrude through hydrodeoxygenation, hydrodenitrogenation, and hydrodesulfurization, producing hydrocarbon fuels.
- Catalytic hydrothermal gasification of the aqueous byproduct stream effectively produced fuel gas and allowed for
The document discusses various aspects of anaerobic wastewater treatment processes. It provides information on the types and characteristics of anaerobic reactors including UASB and EGSB reactors. It also describes the formation of anaerobic granular sludge, which allows high biomass retention and efficient COD removal. Additionally, it compares the kinetics, environmental factors, and advantages of anaerobic versus aerobic wastewater treatment processes.
This document discusses a study on fermenting centipede grass into silage. The objectives were to determine how much acid was produced by bacteria and how much substrate was consumed under anaerobic conditions. Two reactors were used, one with added sucrose and one without. Methods included measuring pH, acidity through titration, and COD over several days. Models were created to simulate biomass formation and product formation in each reactor. Results showed pH increased over time while acid production decreased. COD readings did not follow a clear trend. The added sugar reactor showed higher predicted acid and biomass yields. Limitations may have included paint can contamination and opening reactors for testing.
The document provides an overview of anaerobic digestion, which is a natural process where microorganisms break down organic materials in an oxygen-free environment, producing biogas. It discusses the history of anaerobic digestion from its discovery in the 1600s to current applications. The document also outlines the multi-step digestion process and different technologies used, including liquid, high solids, plug flow, micro, and high rate digestion as well as co-digestion.
This document discusses the design of a system to produce vinegar from excess or damaged peaches. It proposes a two-step fermentation process using yeast to convert sugar to ethanol and then Acetobacter aceti to convert the ethanol to acetic acid. The design includes washing, crushing, and pressing peaches followed by serial fermentation reactors and filtration to produce the vinegar. Byproducts like pomace and carbon dioxide would be sold or composted to increase sustainability. The annual yield is estimated to be 20,059 kg of vinegar per year which could be sold for $1.80 per 32 oz bottle to offset the $21 million startup and $5.8 million annual operating costs.
This document describes a project to design an energy-producing waste treatment system using anaerobic co-digestion of organic wastes from the University of Arkansas Swine and Poultry Units coupled with algae cultivation. A prototype was constructed and tested to generate data for designing a full-scale system. The full-scale system was designed to treat all biological wastes from the units while producing net energy and retaining nutrients that could be used as fertilizer.
Development of a Laboratory Scale Biodiesel Batch ReactorIRJET Journal
The document describes the development of a laboratory-scale batch reactor for biodiesel production. Researchers in Nigeria designed and built a 12-liter reactor using locally available materials to make biodiesel production more accessible. Experiments using the reactor showed that the maximum biodiesel yield was obtained after 20 minutes, and the properties of the biodiesel matched standards. The reactor design incorporated a helical agitator and integrated separation unit to efficiently produce biodiesel from waste vegetable oil on a small scale.
Biogas Production Enhancement from Mixed Animal Wastes at Mesophilic Anaerobi...IJERA Editor
In this work, the effect of mixing ratio of cattle dung (CD) and poultry droppings (PD) on biogas generation was
determined. Mixtures of various CD: PD ratios (100% : 0%; 50% : 50%; 60% : 40%; 80% : 20% and 0% :
100%) were prepared, analyzed and then aerobically digested for a period of 40 days. For each mixture,
fermentation was carried out in a 20 L capacity digester. Results showed that biogas was obtained from the
digestion of CD and PD alone, showing the biogas from CD was several times larger than that from PD.
Furthermore, the resulted biogas yields from mixtures were found a function of the CD : PD ratio, the yield from
the ratio 80 : 20 was the maximum. Biogas yields from the prepared mixtures were found and arranged from
larger to lower in the form of (CD : PD) ratios as follow: 80% : 20%; 100% : 0.0%; 60% : 40%; 0.0% :
100%;50% : 50%. Addition of CD to PD enhances the PD production of biogas, while addition of a small
portion of PD to CD gave the maximum yield, a result not determined in literature. In other hand, larger
additions of PD to CD reduced the biogas yield. The effect of pH was also determined and found better around
7.0. These results are in agreement with research work in literature.
This document presents a comparative study of the performance of activated sludge processes in a bubble column reactor and compact jet loop reactor. Experiments were conducted using synthetic wastewater in laboratory scale models of each reactor type. The chemical oxygen demand (COD) removal efficiency was measured at different mixed liquor volatile suspended solids (MLVSS) concentrations and hydraulic retention times. The results showed that a COD removal efficiency of over 85% could be achieved in the bubble column reactor, and over 95% in the compact jet loop reactor, when operated at an MLVSS of 3000 mg/L and aeration time of 1 hour. The compact jet loop reactor demonstrated better COD reduction performance than the bubble column reactor under the conditions tested.
The document summarizes a seminar presentation on anaerobic digestion of whey waste. The presentation covers: (1) Introduction to anaerobic digestion and characteristics of whey waste; (2) Aims to determine waste reduction, methane yield, and analyze digested sludge; (3) Justification that whey is a pollutant and disposal is costly so it should be treated; (4) Methods which will involve setting up a lab-scale anaerobic digester to produce biogas and analyze methane production.
Dr. Marty Matlock - Lifecycle Assessment of Aquaculture and Aquaponics System...John Blue
Lifecycle Assessment of Aquaculture and Aquaponics Systems in Hawaii and How They Can Improve your Operation - Dr. Marty Matlock, Center for Agricultural and Rural Sustainability, University of Arkansas, from the 2017 NIAA Annual Conference, U.S. Animal Agriculture's Future Role In World Food Production - Obstacles & Opportunities, April 4 - 6, Columbus, OH, USA.
More presentations at http://www.trufflemedia.com/agmedia/conference/2017_niaa_us_animal_ag_future_role_world_food_production
Utilization of pre aerated sludge in activated sludge processeSAT Journals
Abstract The research was carried out with Pre aerated Sludge in Activated Sludge Process to observe the effect of Pre-aerated Sludge on BOD, COD , Phosphate, Nitrate, MLVSS mainly in treatment of dairy wastewater. The experimental process involves the conventional Activated Sludge Process (ASP) in which microorganisms are kept in suspension by mixing and aerating the wastewater. The study is to be conducted by following two methods: 1) utilizing non pre-aerated sludge and 2) utilizing pre-aerated sludge. In the first method the dairy wastewater measuring five liters and 400 ml of non-pre-aerated sludge is filled in the aeration tank and was aerated in the aeration tank where air (or oxygen) was supplied for regular intervals of 30, 60, 90, 120 minutes respectively and samples are collected before aeration and at regular intervals. In the second method the dairy wastewater measuring five liters and 400 ml of pre aerated sludge (with 20, 40 and 60 minutes pre-aeration) are filled in aeration tank. This tank is aerated for regular intervals of 30, 60, 90, 120 minutes respectively. The samples are collected before aeration and at regular time intervals. The sludge is to be not recycled to the aeration tank. Testing of different parameters like BOD, COD, Phosphate, Nitrate and Mixed liquor volatile suspended solids was carried out on the samples aerated with different aeration time, with and without pre-aerated sludge and consequent results are to be found. By utilization of pre-aerated sludge, the concentrations of various parameters to be considered for study are to be found decreased when compared with the values of concentration without using pre-aerated sludge. It will be very clear that removal of various parameters from wastewater is effective up to the optimum period for pre-aeration beyond this period removal of various parameters from wastewater will not be effective. Keywords: Activated Sludge Process, BOD, COD, Phosphate, Nitrate, MLVSS.
The document discusses biofuels, including their need, benefits, and analysis. It provides an introduction to biofuels and their role in reducing carbon emissions. It then discusses the need for biofuels in terms of their ease of use in vehicles, ability to provide energy security, potential for economic development, and ability to reduce greenhouse gas emissions. However, biofuels also face objections regarding their economic viability and environmental impacts. The document concludes by discussing life cycle analysis of biofuels and perspectives on biodiesel.
Dr. Greg Thoma - An Overview of Aquaculture through the lens of Environmental...John Blue
An Overview of Aquaculture through the lens of Environmental Sustainability - Dr. Greg Thoma, University of Arkansas, College of Engineering, from the 2018 NIAA Annual Conference, Livestock Traceability: Opportunities for Animal Agriculture, plus the Traceability and the Real World Interactive Workshop, April 10 - 12, Denver, CO, USA.
More presentations at https://www.youtube.com/channel/UCeUDeS810OcOfuEYwj1oHKQ
This document summarizes the results of a life cycle assessment (LCA) comparing bioplastic containers to petroleum-based containers. The LCA analyzed the environmental impacts from cradle-to-gate and partial cradle-to-grave. For the cradle-to-gate analysis, bioplastics made from PLA, PHA, and various biocomposite formulations were compared to polypropylene containers. The LCA found that the bioplastics generally had higher global warming and fossil fuel impacts than polypropylene, though some formulations like PLA-SPA-BioRes performed better. A partial cradle-to-grave analysis considered various end-of-life scenarios for the containers.
Anaerobic Digestion: Co-Digestion and Operational Issues LPE Learning Center
Proceedings available at: http://www.extension.org/67744
A study was conducted to assess the performance of various mixing regimes on methanogen biomass content in anaerobic digesters. Methane production in anaerobic digesters is directly related to the methanogens within the system. Current systems involve mixing to increase biogas production and system efficiency, however little is known about the underlying mechanisms of this relationship. In this study three pilot scale anaerobic digestion systems with three different mixing regimes were run with replication to examine the impacts to methanogen biomass content and biogas production. The results will provide insight for operational recommendations as well as the basic microbial processes with digestion systems which are critical for optimization.
This document presents information on upflow anaerobic sludge blanket (UASB) reactors. It discusses that the UASB technology was developed in the 1970s to treat industrial and sewage wastewater using anaerobic digestion. The key factors affecting UASB reactor performance are identified as organic loading rate, nutrients, hydraulic retention time, volatile fatty acids, operational temperature, and operational pH. Advantages of UASB reactors include high efficiency, simplicity, flexibility, low space and energy requirements, and low sludge production, while disadvantages include low pathogen/nutrient removal, long start-up times, potential for odors, and need for post-treatment.
Algal biomass can be used to produce biogas through anaerobic digestion, providing a renewable source of energy. The biogas production process involves four key stages - hydrolysis, acidogenesis, acetogenesis, and methanogenesis - where bacteria break down the algal biomass into methane gas. The end products include biogas, digestate fertilizer, and water, providing alternatives to fossil fuels and chemical fertilizers while reducing greenhouse gas emissions.
Methane and power produced from anaerobic digestion of algae can be used to generate electricity and reduce greenhouse gas emissions. Algae grow quickly and absorb carbon dioxide, so the carbon released from burning the biogas was recently absorbed by the algae and is part of a carbon-neutral cycle. Anaerobic digestion of algae involves breaking down the algae into biogas in an oxygen-free tank, then collecting and using the methane gas. The remaining digestate has applications as fertilizer. Overall, algal production for biogas is a sustainable process that generates renewable energy while recycling carbon dioxide.
Biogas Generation and Factors Affecting Global WarmingIRJET Journal
This document discusses biogas generation and its role in reducing global warming. It begins by introducing biogas as a mixture of methane and carbon dioxide produced through anaerobic digestion of organic waste. This process reduces pollution and global warming by converting methane into energy. The document then discusses the factors that affect biogas production, including temperature, retention time in digesters, and types of digestion systems. Maintaining the optimal temperature range in digesters and sufficient retention time are important for efficient biogas generation through anaerobic digestion.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Micro-Scale Biogas Production: A Beginner's GuideGardening
This document provides an introduction and overview of micro-scale biogas production through anaerobic digestion. It discusses how anaerobic digestion works, factors that influence the process like temperature and pH, appropriate feedstocks, and several common designs for simple household or farm-scale digesters. The designs described include a polyethylene tube trench digester and an in-ground dome design, both of which are low-cost options used in developing countries. The document aims to demonstrate how small-scale biogas production can provide renewable energy and fertilizer while reducing dependence on fossil fuels.
Wastewater treatment plants can produce renewable biogas energy through anaerobic digestion of sewage sludge and other organic waste. The biogas can be used to generate electricity and heat on-site through combined heat and power systems, reducing energy costs and emissions. Larger regional facilities may provide greater economies of scale for energy production compared to plant-by-plant solutions. Proper operation and monitoring of digestion systems optimizes biogas yield and renewable energy output.
This presentation discusses biogas production from garbage through anaerobic digestion. It defines biogas as a combustible gas produced through biological breakdown of organic matter without oxygen. The presentation outlines the four stages of anaerobic digestion: hydrolysis, acidogenesis, acetogenesis, and methanogenesis. It also discusses factors that affect biogas production such as temperature, pH, carbon/nitrogen ratio, organic loading rate, and hydraulic retention time. Applications of biogas include electricity generation, transportation fuel, and cooking fuel.
Biogas is produced through anaerobic digestion of organic matter without oxygen. It primarily consists of methane and can be used as an renewable energy source. Biogas can be produced on farms through anaerobic digesters and provides benefits like renewable energy, reduced pollution, and jobs in rural areas. While small scale biogas production has high costs, large scale anaerobic digestion is economically viable to produce biogas for heat, electricity, and transportation.
Biogas is produced after organic materials (plant and animal products) are broken down by bacteria in an oxygen-free environment, a process called anaerobic digestion. Biogas systems use anaerobic digestion to recycle these organic materials, turning them into biogas, which contains both energy (gas), and valuable soil products (liquids and solids).
IRJET- Design of Organic Compost MachineIRJET Journal
This document describes the design of an organic compost machine. The machine uses special microorganisms to decompose organic waste into compost within 24 hours, achieving an 85-90% volume reduction. The machine has a U-shaped composting tank with a humidity sensor, heater, mixing blades, and exhaust system. When organic waste is added, the humidity sensor detects moisture and turns on the heater to evaporate water from the waste. Microorganisms then decompose the waste into compost within 24 hours. The process is contained and odorless. The design aims to efficiently manage food waste and produce nutrient-rich compost within a day.
Anaerobic digestion to biogas renewable energy resources defDrBilalAhmadZafarAmi
This document summarizes a lecture on renewable energy resources, focusing on anaerobic digestion of biomass to produce biogas. It discusses Pakistan's biomass waste potential and mechanisms of anaerobic digestion. It also outlines different anaerobic digestion system types based on factors like loading schedule and temperature. Commonly used anaerobic digestion technologies globally and in Pakistan are presented, including liquid, high solids, plug flow, and micro digestion systems. Site selection factors for biogas plants and classifications of biogas plants are also summarized.
This document provides information about a biogas plant report prepared by a student. It begins with an introduction to biogas and biogas plants. It then discusses what biogas is, the constituents of biogas, how a biogas plant works, and the advantages and disadvantages of biogas plants. Some key points covered include:
- Biogas is produced from the anaerobic digestion of organic waste by bacteria in an oxygen-free environment. It is comprised primarily of methane and carbon dioxide.
- A biogas plant consists of a digester where waste decomposes and a gas holder that collects the gases produced. The gases can then be used as an energy source.
- Biogas plants reduce waste,
The document discusses using algae for biofuel production through heterotrophic growth. It notes that some companies are establishing infrastructure for heterotrophic algae growth, which does not require sunlight. The key advantages are that heterotrophic algae growth requires less space, allows for higher cell concentrations, and offers more control over the feedstock and resulting fuel properties compared to photosynthetic growth. The document also outlines methods for pyrolysis of algae and notes that algae oils can have applications beyond fuel such as in personal care products, surfactants, and more.
The document discusses biorenewable gaseous fuels, focusing on biogas produced through anaerobic digestion. It describes the multi-step anaerobic digestion process where organic materials are broken down by microorganisms into methane and carbon dioxide biogas. Key points include: Anaerobic digestion is well established and involves hydrolysis of materials into sugars and acids, followed by acetogenesis and methanogenesis to produce biogas. Biogas can be processed and used as an energy source, though it also contains impurities. Maintaining proper temperature, pH and nutrient levels is important for optimal microbial activity in anaerobic digestion.
This document discusses biogas plants as an alternative energy source, particularly for rural India. It begins with an introduction on the need for alternative energy due to depletion of fossil fuels. It then provides details on how biogas is generated through anaerobic digestion of organic waste in a biogas plant. The four key stages of biogas generation are hydrolysis, acidogenesis, acetogenesis, and methanogenesis. Finally, it discusses different types of biogas plants, focusing on batch and continuous systems, explaining their characteristics and operation.
Anaerobic digestion is a microbiological process where organic matter decomposes in the absence of oxygen. Through controlled engineering, anaerobic digestion breaks down organic biodegradable matter in sealed reactor tanks to produce biogas and digestate. The four-stage digestion process involves hydrolysis, acidogenesis, acetogenesis, and methanogenesis where anaerobic microorganisms biochemically digest materials like glucose into methane and carbon dioxide. Anaerobic digestion generates renewable energy as biogas and nutrient-rich digestate fertilizer.
This document defines key terms and concepts related to energy and material flow through ecosystems. It explains that:
1) Photosynthesis uses sunlight, carbon dioxide, and water to produce oxygen and sugars (glucose) through a light-to-chemical energy transformation, while respiration uses sugars and oxygen to produce carbon dioxide, water, and energy through a chemical-to-heat transformation.
2) Energy from the sun is transformed through photosynthesis, storing energy in glucose that producers then use and transform further through respiration to power their life processes. This energy then passes to consumers as they eat producers or other organisms.
3) Productivity terms measure the rate of biomass growth or energy accumulation in ecosystems, with primary productivity referring
Factors affecting biogas production during anaerobic decomposition of brewery...Alexander Decker
This document summarizes a study that analyzed factors affecting biogas and carbon dioxide production during anaerobic decomposition of brewery wastewater in a fluidized bed digester. The study monitored gas production at different microbial concentrations, hydraulic retention times, and volatile fatty acid to alkalinity ratios. Maximum gas volumes were recorded at 8 hours hydraulic retention time, corresponding to favorable operating conditions and good system stability. The biogas produced was rich in methane and could potentially be integrated into the brewery's energy mix to improve process economics.
A New World... World not built around CarbonRita EL Khoury
This research paper is conducted to develop the concept of bio-fuels. Bio-fuels are a renewable source of energy made from recently living biomass. According to the literature, different production processes exist leading to different types of bio-fuels. However, this research paper focuses on the two most common types: bio-ethanol and bio-diesel. The most efficient industrial production process adding to it the environmental and the economical impact are analyzed for each of these gasoline replacements.
Being a Chemical Engineer taking courses in petroleum engineering and knowing the pros and cons of this hydrocarbon energy, pushed me to work on this paper as I do believe that we should be confronting the energy crisis before it reaches its peak. In this paper, the ways of producing bio-fuels are introduced by:
- Identifying the raw materials present in the feed stock.
- Establishing the chemical process.
- Pointing out the advantages of biofuels.
- Discussing the economical impact of biofuels.
This document provides information about prestressed concrete storage tanks from DNTanks. It discusses DNTanks' construction procedures, the benefits of prestressed concrete tanks, and applications. DNTanks is the largest manufacturer of prestressed concrete tanks in the world, with over 130 years of combined experience constructing over 2,500 tanks globally. Prestressed concrete tanks provide benefits like being leak-free, requiring less maintenance than steel tanks, and allowing various installation methods. The document also discusses inspection and retrofitting of existing concrete tanks.
This document provides an overview of various concrete storage structures constructed using VSL's specialized construction methods, including slipforming, post-tensioning, and heavy rigging. It describes over 40 completed tank projects storing liquids like water, sewage, and fuels, as well as solid materials like cement, coal, and sugar. VSL's methods offer advantages like rapid, economical, and dimensionally accurate construction of monolithic concrete structures. Applicable to tanks and towers at or near ground level, slipforming allows continuous construction. Post-tensioning increases structural efficiency. The document aims to illustrate the suitability and advantages of concrete tanks and to explain VSL's construction capabilities.
Dutchland, Inc. is a precast concrete manufacturer that specializes in post-tensioned concrete structures using certified personnel. They produce tanks for water storage and wastewater treatment that are virtually maintenance-free for decades, requiring minimal site space and less construction time compared to cast-in-place. All structures are warranted for 10 years and can be constructed above or below ground in various configurations to meet specific needs.
The report summarizes groundwater, surface water, and leachate monitoring data collected between April 2009 and March 2010 at the Hartland landfill and surrounding area. Key findings include: (1) Groundwater flow patterns were consistent with previous years, with some northward and southeastward flow captured by purge wells. (2) Groundwater quality showed contained leachate impacts. (3) Elevated parameters near the Hartland North Pad indicated ongoing impacts from historical composting and current aggregate stockpiling. Water quality is closely monitored.
The document discusses the benefits of exercise for both physical and mental health. Regular exercise can help reduce the risk of diseases like heart disease and diabetes while also improving mood and reducing stress and anxiety. Exercising for at least 30 minutes per day several times a week is recommended to gain these health benefits.
This document provides exceptions to the Canadian Highway Bridge Design Code (CHBDC) for use in Ontario. It establishes the scope and authority of the exceptions, and implementation procedures. Section 4 lists specific exceptions to clauses in the CHBDC, modifying or replacing language as it applies to standards and practices for bridges in Ontario. Exceptions are provided for general administrative definitions, single load path structures, plan requirements, geometry, barriers, hydraulic design, foundations, buried structures, concrete structures, and steel structures. Appendix A provides additional exceptions for low volume roads.
Microbial characterisation and identification, and potability of River Kuywa ...Open Access Research Paper
Water contamination is one of the major causes of water borne diseases worldwide. In Kenya, approximately 43% of people lack access to potable water due to human contamination. River Kuywa water is currently experiencing contamination due to human activities. Its water is widely used for domestic, agricultural, industrial and recreational purposes. This study aimed at characterizing bacteria and fungi in river Kuywa water. Water samples were randomly collected from four sites of the river: site A (Matisi), site B (Ngwelo), site C (Nzoia water pump) and site D (Chalicha), during the dry season (January-March 2018) and wet season (April-July 2018) and were transported to Maseno University Microbiology and plant pathology laboratory for analysis. The characterization and identification of bacteria and fungi were carried out using standard microbiological techniques. Nine bacterial genera and three fungi were identified from Kuywa river water. Clostridium spp., Staphylococcus spp., Enterobacter spp., Streptococcus spp., E. coli, Klebsiella spp., Shigella spp., Proteus spp. and Salmonella spp. Fungi were Fusarium oxysporum, Aspergillus flavus complex and Penicillium species. Wet season recorded highest bacterial and fungal counts (6.61-7.66 and 3.83-6.75cfu/ml) respectively. The results indicated that the river Kuywa water is polluted and therefore unsafe for human consumption before treatment. It is therefore recommended that the communities to ensure that they boil water especially for drinking.
Recycling and Disposal on SWM Raymond Einyu pptxRayLetai1
Increasing urbanization, rural–urban migration, rising standards of living, and rapid development associated with population growth have resulted in increased solid waste generation by industrial, domestic and other activities in Nairobi City. It has been noted in other contexts too that increasing population, changing consumption patterns, economic development, changing income, urbanization and industrialization all contribute to the increased generation of waste.
With the increasing urban population in Kenya, which is estimated to be growing at a rate higher than that of the country’s general population, waste generation and management is already a major challenge. The industrialization and urbanization process in the country, dominated by one major city – Nairobi, which has around four times the population of the next largest urban centre (Mombasa) – has witnessed an exponential increase in the generation of solid waste. It is projected that by 2030, about 50 per cent of the Kenyan population will be urban.
Aim:
A healthy, safe, secure and sustainable solid waste management system fit for a world – class city.
Improve and protect the public health of Nairobi residents and visitors.
Ecological health, diversity and productivity and maximize resource recovery through the participatory approach.
Goals:
Build awareness and capacity for source separation as essential components of sustainable waste management.
Build new environmentally sound infrastructure and systems for safe disposal of residual waste and replacing current dumpsites which should be commissioned.
Current solid waste management situation:
The status.
Solid waste generation rate is at 2240 tones / day
collection efficiently is at about 50%.
Actors i.e. city authorities, CBO’s , private firms and self-disposal
Current SWM Situation in Nairobi City:
Solid waste generation – collection – dumping
Good Practices:
• Separation – recycling – marketing.
• Open dumpsite dandora dump site through public education on source separation of waste, of which the situation can be reversed.
• Nairobi is one of the C40 cities in this respect , various actors in the solid waste management space have adopted a variety of technologies to reduce short lived climate pollutants including source separation , recycling , marketing of the recycled products.
• Through the network, it should expect to benefit from expertise of the different actors in the network in terms of applicable technologies and practices in reducing the short-lived climate pollutants.
Good practices:
Despite the dismal collection of solid waste in Nairobi city, there are practices and activities of informal actors (CBOs, CBO-SACCOs and yard shop operators) and other formal industrial actors on solid waste collection, recycling and waste reduction.
Practices and activities of these actor groups are viewed as innovations with the potential to change the way solid waste is handled.
CHALLENGES:
• Resource Allocation.
Presented by The Global Peatlands Assessment: Mapping, Policy, and Action at GLF Peatlands 2024 - The Global Peatlands Assessment: Mapping, Policy, and Action
Evolving Lifecycles with High Resolution Site Characterization (HRSC) and 3-D...Joshua Orris
The incorporation of a 3DCSM and completion of HRSC provided a tool for enhanced, data-driven, decisions to support a change in remediation closure strategies. Currently, an approved pilot study has been obtained to shut-down the remediation systems (ISCO, P&T) and conduct a hydraulic study under non-pumping conditions. A separate micro-biological bench scale treatability study was competed that yielded positive results for an emerging innovative technology. As a result, a field pilot study has commenced with results expected in nine-twelve months. With the results of the hydraulic study, field pilot studies and an updated risk assessment leading site monitoring optimization cost lifecycle savings upwards of $15MM towards an alternatively evolved best available technology remediation closure strategy.
ENVIRONMENT~ Renewable Energy Sources and their future prospects.tiwarimanvi3129
This presentation is for us to know that how our Environment need Attention for protection of our natural resources which are depleted day by day that's why we need to take time and shift our attention to renewable energy sources instead of non-renewable sources which are better and Eco-friendly for our environment. these renewable energy sources are so helpful for our planet and for every living organism which depends on environment.
Kinetic studies on malachite green dye adsorption from aqueous solutions by A...Open Access Research Paper
Water polluted by dyestuffs compounds is a global threat to health and the environment; accordingly, we prepared a green novel sorbent chemical and Physical system from an algae, chitosan and chitosan nanoparticle and impregnated with algae with chitosan nanocomposite for the sorption of Malachite green dye from water. The algae with chitosan nanocomposite by a simple method and used as a recyclable and effective adsorbent for the removal of malachite green dye from aqueous solutions. Algae, chitosan, chitosan nanoparticle and algae with chitosan nanocomposite were characterized using different physicochemical methods. The functional groups and chemical compounds found in algae, chitosan, chitosan algae, chitosan nanoparticle, and chitosan nanoparticle with algae were identified using FTIR, SEM, and TGADTA/DTG techniques. The optimal adsorption conditions, different dosages, pH and Temperature the amount of algae with chitosan nanocomposite were determined. At optimized conditions and the batch equilibrium studies more than 99% of the dye was removed. The adsorption process data matched well kinetics showed that the reaction order for dye varied with pseudo-first order and pseudo-second order. Furthermore, the maximum adsorption capacity of the algae with chitosan nanocomposite toward malachite green dye reached as high as 15.5mg/g, respectively. Finally, multiple times reusing of algae with chitosan nanocomposite and removing dye from a real wastewater has made it a promising and attractive option for further practical applications.
Optimizing Post Remediation Groundwater Performance with Enhanced Microbiolog...Joshua Orris
Results of geophysics and pneumatic injection pilot tests during 2003 – 2007 yielded significant positive results for injection delivery design and contaminant mass treatment, resulting in permanent shut-down of an existing groundwater Pump & Treat system.
Accessible source areas were subsequently removed (2011) by soil excavation and treated with the placement of Emulsified Vegetable Oil EVO and zero-valent iron ZVI to accelerate treatment of impacted groundwater in overburden and weathered fractured bedrock. Post pilot test and post remediation groundwater monitoring has included analyses of CVOCs, organic fatty acids, dissolved gases and QuantArray® -Chlor to quantify key microorganisms (e.g., Dehalococcoides, Dehalobacter, etc.) and functional genes (e.g., vinyl chloride reductase, methane monooxygenase, etc.) to assess potential for reductive dechlorination and aerobic cometabolism of CVOCs.
In 2022, the first commercial application of MetaArray™ was performed at the site. MetaArray™ utilizes statistical analysis, such as principal component analysis and multivariate analysis to provide evidence that reductive dechlorination is active or even that it is slowing. This creates actionable data allowing users to save money by making important site management decisions earlier.
The results of the MetaArray™ analysis’ support vector machine (SVM) identified groundwater monitoring wells with a 80% confidence that were characterized as either Limited for Reductive Decholorination or had a High Reductive Reduction Dechlorination potential. The results of MetaArray™ will be used to further optimize the site’s post remediation monitoring program for monitored natural attenuation.
Epcon is One of the World's leading Manufacturing Companies.EpconLP
Epcon is One of the World's leading Manufacturing Companies. With over 4000 installations worldwide, EPCON has been pioneering new techniques since 1977 that have become industry standards now. Founded in 1977, Epcon has grown from a one-man operation to a global leader in developing and manufacturing innovative air pollution control technology and industrial heating equipment.
Improving the viability of probiotics by encapsulation methods for developmen...Open Access Research Paper
The popularity of functional foods among scientists and common people has been increasing day by day. Awareness and modernization make the consumer think better regarding food and nutrition. Now a day’s individual knows very well about the relation between food consumption and disease prevalence. Humans have a diversity of microbes in the gut that together form the gut microflora. Probiotics are the health-promoting live microbial cells improve host health through gut and brain connection and fighting against harmful bacteria. Bifidobacterium and Lactobacillus are the two bacterial genera which are considered to be probiotic. These good bacteria are facing challenges of viability. There are so many factors such as sensitivity to heat, pH, acidity, osmotic effect, mechanical shear, chemical components, freezing and storage time as well which affects the viability of probiotics in the dairy food matrix as well as in the gut. Multiple efforts have been done in the past and ongoing in present for these beneficial microbial population stability until their destination in the gut. One of a useful technique known as microencapsulation makes the probiotic effective in the diversified conditions and maintain these microbe’s community to the optimum level for achieving targeted benefits. Dairy products are found to be an ideal vehicle for probiotic incorporation. It has been seen that the encapsulated microbial cells show higher viability than the free cells in different processing and storage conditions as well as against bile salts in the gut. They make the food functional when incorporated, without affecting the product sensory characteristics.
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Table of Contents
1. Introduction ............................................................................................................................. 3
2. Types of Digesters .................................................................................................................. 6
3. Settings for Digesters............................................................................................................. 7
4. Digester Tank Design ............................................................................................................. 8
5. Digestate Management ...................................................................................................... 12
6. Gas Upgrading & Handling................................................................................................. 14
7. Gas Use.................................................................................................................................... 17
8. Project Development and Finance................................................................................... 19
9. Digester Construction Methodology............................................................................... 19
11. US Project Examples.......................................................................................................... 22
12. Appendix............................................................................................................................... 26
About the Author...................................................................................................................... 27
Acknowledgements:................................................................................................................. 27
The latest update of this EBook is always available at www.digester.com. Tune to our podcast on digester.com and on ITunes for
interviews with leading edge facility operators.
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1. INTRODUCTION
Biogas comes from the breakdown of organic matter in anaerobic
environments such as in landfills, in nature, in the human body, and in
engineered anaerobic digesters. Anaerobic Digestion (AD) is the breakdown
of organic matter in the absence of oxygen. AD units come in many different
styles, shapes and configurations with the commonalities being that they
operate in the absence of oxygen, in a sealed vessel and operate at elevated
temperatures. A common analogy is that food waste digesters operate quite
like the human body's or ruminant animal's digestive system. The gas
mixture that emanates from a digester is commonly referred to as biogas.
The remaining solids and nutrient rich liquid is referred to as digestate. This
document is focused on AD as an established means of converting organic
matter to fertilizer and biogas.
Food waste is a common material used to feed digesters. A common pyramid for dealing with excess food is:
a. Feed People
b. Feed Animals
c. Generate Energy (send to a digester)
d. Produce Compost
AD is turning into an ever-popular recycling choice as an approach to get energy, compost and nutrient value out of discarded
organics and helps control methane emissions which are a highly potent greenhouse gas. Biogas can be used as a fuel in gas
pipelines, combusted to produce electricity or compressed into a vehicle fuel. The residual solids and liquid are good nutrient-rich
crop fertilizers.
1.1 PROCESS CHEMISTRY
The pathway to making biogas from waste is multi-step. First, the
organic waste undergoes hydrolysis and acidification steps where large
molecules are broken apart and organic acids are formed. Material at
this phase would have a foul odor to it and be considered "rancid.”
From there, other steps including acetogeneis and methanization occur
where microbes called "acetogens" and "methanogens" generate
methane gas. The acetogenesis phase converts organic acids to
acetate. Methanogens are the key to making biogas but are slow
growing and can cause operational issues if not tended to properly.
Biogas is commonly a mix of both methane and carbon dioxide (CO2).
The compositions of biogas depend on the chemical pathway for
digestion but usually range from 50-70% for methane with the balance
being CO2, hydrogen sulfide and other trace gases.
1.2 GAS YIELD
Wastes make different amounts of gas in a digester. Gas yields are fairly analogous to calorie value of foods as both pertain to
energy values. In a digester, easy to digest carbohydrates such as pre consumer food waste from grocery stores can digest very
Steps in AD Process
Food Waste to a Digester
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rapidly and convert to methane quickly much like our bodies metabolize sugars and starches quickly. Other materials like
proteins in waste meat or waste oils and fats can provide very significant energy potential but can take more time to degrade.
A common lab test to validate the potential gas yield of these various substrates is the Biomethane Potential Test, or BMP Test.
The BMP test simulates a digester on the laboratory scale as a batch test. A waste sample is put in a sealed beaker, diluted,
seeded with a bacteria inoculum, heated, and mixed for a number of weeks. Its resulting gas yield rate is traced over time.
Knowing the BMP profile of the waste with a particular process is critical to modeling system gas output. There is significant data
in industry literature on the gas yield of hundreds of different substrates.
To understand how gas comes from food waste one can come at it from a couple of perspectives. First one must appreciate that
food waste can contain 60-90% water. The remaining fraction is the material that provides the gas yield. A ton of food waste that
enters a digester will only yield gas from the Volatile Fraction, that being the carbonaceous fraction. Some will refer to the gas
yield of a wet ton of matter delivered to a facility while others will refer to gas yield that comes from volatile fraction not
including the water weight. The first would be considered the gas yield of "wet solids" the other would be considered the gas
yield of the "volatile solids.”
1.3 PROCESS MODELING
A number of digester computer-based performance models exist. Some are available for a fee and others are available for
download at no cost. A process model is a key step in the typical stage-gated project development process where local area
wastes are profiled and waste quantities are projected. By inputting projected tip fees, resulting energy and compost sales,
projected Return on Investment (ROI) can be calculated to determine if a project meets investor financial metrics.
Running a number of iterations of the process model to optimize the local circumstances and nuances of a particular project are
of paramount importance to optimizing digestion facility size. As all models can be subject to "Garbage In - Garbage Out"
scenarios it is important to feed the models with good, hard costing information of system construction cost, projected energy
sales and projected site tip fees to make educated decisions. Many of the free models work fine for project screening but once
projects get past the screening stage and into the project sizing stage, these models become too complex for the no-cost models.
1.4 DIGESTION PROCESS
"Volatile Solids" are the components of the wastes that are amenable to converting to gas. These are different from the non-
volatile fraction, also known as the ash fraction. Much as the volatile fraction of woody waste goes up in smoke in a fireplace, for
example, the ash is the fraction which is left behind and not able to be volatilized. Digester designers require data on organic
matter concentrations in feedstocks and project what fraction of the organics can convert to biogas. Roughly 40-60% of the
organic matter or "volatile fraction" of the feedstock will convert to gas in the digester, given proper residence time. The more
time the waste is allowed to digest in the system the more the conversion. Some molecules like cellulose and other fibrous
material will sometimes resist breakdown in a digester but given the right conditions can be digested.
There is a tradeoff and balance between the amount of digestion time, the amount of energy one is able to produce and system
costs.
1.4.1 LOADING RATES
A recent Cal Recycle study gives reference on loading rates used in anaerobic digesters. Loading rates they refer to include 0.02-
0.05 pounds of volatile solids per gallon of digester tank volume each day.
Example: Loading rate of food waste into a 1 Million gallon digester:
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Assuming a food waste that was 70% water, 15% volatile solids and 15% nonvolatile (ash)
Assume a mid loading rate of 0.025 lb. of volatile solids per gallon of digester volume daily
As the food waste is 15% volatile one must first convert to total mass of food waste. That equates to 0.025/0.15 or 0.167
pounds of total food waste (or 2.6 ounces) per gallon of digester capacity each day.
So, for example, a typical 1 Million gallon digester tank might have about 167,000 wet pounds (1,000,000 gallons x 0.167
pounds per gallon per day loading rate) or 83 wet tons of food waste fed to it each day at these loading rates.
Common reactor retention times range from as little as a few days to as much as a month or two. The loading rate and retention
time varies with the type of waste and the type of digester being used.
1.4.2 GAS YIELD
A study from Sweden (Substrate Handbook 2009) quoted about shows that showed an average gas yield of 3.6 cubic of biogas
would come from the digestion of a pound of typical food waste:
Example: Gas Yield and Power Generation capacity for a large, 40,000 ton per year food waste digester:
40,000 ton / yr. x 2000 lb. /ton = 80,000,000 lb./yr. total food waste fed into digester
80,000,000 lb. of food waste x 3.6 cubic feet per pound = 288 million cubic feet per year of gas generated
288 Million cubic feet of biogas per year is 555 cubic feet per minute (SCFM)
Field data has shown a typical power gen system can produce 300 KW of power from 100 CFM of gas at typical efficiencies
(Bevington, 2013).
Electric Generation - Therefore a system that produces 555 CFM will produce (550/100 CFM or a 5.5 x factor) or 5.5 x
300KW or 1.65 Megawatts of electricity.
Vehicle Fuel - The same 555 SCFM of biogas = 800,000 cubic feet per day. Assuming 550 BTU in each cubic foot gives 440
Million BTU/day which also = 3140 GGE or gallon of gas equivalent (assuming 140,000 btu per gallon) of vehicle fuel.
In summary, one can get either 3140 gallons equivalent of vehicle fuel or 1.6 MW of electricity daily from 40,000 tons per
year of food waste in this case. The decision of which to produce would depend on local economics. If, for example, the
value of electricity was 8 cents per kilowatt-hour the value of this electricity would be $3168 per day. If in this case vehicle
fuel was valued at about $2 per gallon the value of this fuel would be about $6280 per day. It is also worth noting that the
vehicle fuel scenario incurs extra scrubbing costs, gas compression and extra digester heating costs compared to the
electricity scenario.
1.5 SUBSTRATES AND FEEDSTOCKS
Just as in the human body, anaerobic digesters are best fed a variety of substrates for a proper balanced "diet." This mix can
provide a balanced, buffered feed which makes a digester less prone to upset. Digesters function well with a baseload substrate
like municipal biosolids, animal manure or energy crops as they promote process stability. High energy feedstocks like fats and
oils are typically a minority of the feed load due to process stability and buffering concerns.
References:
CalRecylcle http://www.calrecycle.ca.gov/Publications/Documents/Organics%5C2008011.pdf page 52, Swedish Handbook
http://www.avfallsverige.se/fileadmin/uploads/Rapporter/Utveckling/U2009-14.pdf Page 31 translated from Swedish by Google Translate. Substrate Handbook for
Biogas Production, 2009, Gloversville Johnstown JWTP, 2013, Data from George Bevington, Operations Manager.
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2. TYPES OF DIGESTERS
There are many configurations of anaerobic digesters and can run at different target temperatures the most common of which
are Mesophillic (95 F, 35 C) or Thermophilic (125 F, 50C). There are different populations of anaerobic microbes that thrive in
these temperature zones. Digesters can combine all the main process chemistry steps (hydrolysis, acidification, acetogenisis,
methanogenis) either in a single process reactor tank or in two separated reactor tanks. While separation of digestion phases
allows for some additional process control, it incurs additional capital costs for the additional tanks and monitoring.
2.1 WET DIGESTERS
The most common digester style is called a "Wet Digester.” They are known
as "wet" due to all the substrates being able to be moved around as liquid
slurries and mixed by pumps. The consistency of these digesters contents is
usually 3-15% total solids. Typical retention times range from 20-40 days.
Farm based digesters also come in lagoon or in-ground plug flow reactors. A
newer digester style is an Anaerobic Membrane Bioreactor (AnMBR) that
uses a membrane filter at the back end of the facility to separate reactor
slurry solids from the digestate liquids and hold solids in the system. Yet
another system is a multi-phased digester with hydrolysis step and a
methanogenesis step, sometimes with interstage solids separation of inert
solids, which can allow for optimized residence time.
2.2 DRY DIGESTERS
Dry digesters keep the substrates in a stackable form and remain in a pile
during the digestion process. Food waste is mixed with green wastes such as
yard debris for structure and porosity and is put into a long, rectangular
vessel in a stack. The vessel is then sealed tight and warmed. Warm water, or
percolate, is sprayed over the waste stack, collected and recycled. The
percolate is biologically active which accelerates the digestion process.
Percolate is sent to a separate methanization digester tank where the biogas
is generated and the percolate recycled. There are also vertical down-flow
reactor configurations where waste is fed in the top and allowed to flow out
the bottom a number of days later while digesting along the way.
Dry Digester System
Front Door of Dry Digester Emptying Contents from Dry Digester Dry Digester Opened Doors
Wet Style Digester
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3. SETTINGS FOR DIGESTERS
3.1 MUNICIPAL WASTEWATER TREATMENT FACILITIES
Municipal treatment facilities commonly operate anaerobic digesters to convert the bulk of the volatile solids in their sludges to a
form that is more stable, has less volume, easier to dewater and reduced pathogens. Some municipalities have additional
available treatment volume and can take in outside substrates to gain tipping fees and increase energy production. Common
outside wastes taken by municipal treatment plants include food scraps, cheese and yogurt whey, beverage wastes, fats, oils &
grease (FOG) from sources like restaurant grease traps.
3.2 FARM BASED UNITS
Farmers have seen that anaerobic digestion can be an effective way to deal with dairy, swine and
poultry manures. The typical cow generates 20 gallons of manure each day. A large 2000 head
dairy farm, for example, can generate sizable quantities of manure. Digesters are able to reduce
manure odors, convert organic matter to energy, reduce pathogens, return solid bedding
materials to the barns and convert the nutrients from manure into more usable form. Farmers
are also realizing revenue opportunities in receiving outside feedstocks to feed into their digester
to increase gas yield. One thing for farms to be mindful of, however, are the additional nutrients
found in these outside substrates, as they will require proper management out the back end of
the digester.
3.3 MERCHANT FACILITIES
A number of merchant digestion facilities have started up in recent years
that take in food scraps as their predominant feedstock. These are materials
that would usually otherwise have been landfilled or composted. Sending
this material first to AD gives it a chance to supply renewable energy, odor
reduction and waste stabilization on the way to further composting. Other
popular substrates to these merchant facilities include brown grease, food
industry processing residuals (i.e. dissolved air flotation float), and
wastewater treatment residuals.
3.4 INDUSTRIAL - HIGH STRENGTH WASTES
Many food and beverage industries commonly have an anaerobic treatment system in the back of their facility. For example,
most breweries have anaerobic digesters. Many big protein processors will incorporate large anaerobic lagoons into their
operations with long detention times to achieve breakdown of protein-laden wastes.
3.5 COMMERCIAL / INSTITUTIONAL
Large institutions such as universities, resorts and others can install their own anaerobic digestion systems. AD can help drive
these institutions to help meet their Climate Action plans and make them more carbon neutral and more sustainable. Often
several campus utility vehicles can be fueled by installing one's own digester and converting food scraps to vehicle fuel. These can
be great education opportunities for area students, are useful community showpieces and generate compost for local use. A
good sized institutional digester can routinely generate the equivalent of 100-200 gallons of liquid fuel equivalent to fuel on-site
vehicles.
Centrifuge at Dairy Digest Happy
Farm Digester User
Large Urban Merchant Facility
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4. DIGESTER TANK DESIGN
4.1 HEATING
Digesters need to be kept warm for proper bacteriological function. Heating
coils can be mounted inside the tank itself or placed within concrete tank
walls. External heat exchangers can also be used and can include a plate and
frame, spiral or shell-in-tube designs. Ideally excess heat is used from the
facilities' combined heat and power (CHP) unit to keep the tank warm, year
round. Direct steam injection is also done by injecting steam into a recycle
loop. For systems without CHP units or other sources of heat, a boiler system
may be required for ongoing heat. A heat source should be considered for
system startup.
4.2 MIXING
Good mixing is important for digesters to ensure proper stirring of the tank,
suspension of heavier solids and proper contact between the microbes and
the waste. Mixing time can vary from continuous to periodic to save on
power costs. Various configurations of mixers are widely adopted in digester
design and should be considered a major point of focus for the system's long
term reliability and mechanical integrity. Over-mixing can be an issue where
excess mixing intensity can de-stabilize the microbes and lead to process
upset. Some digester projects will incorporate a combination of the
following mixing techniques in a given project.
4.2.1 MECHANICAL
Mechanical agitation can be done via a vertical shaft hanging from a fixed digester roof or by a side-mounted propeller style
mixers penetrating the tank wall. Submersible mechanical mixers can be mounted on rails connected to the interior tank wall
that allow for easy removal from the basin for maintenance. These mixers can be powered by a motor or by high pressure
hydraulics. Another style is a mechanical agitator mixer that is on a short shaft mounted inside the digester basin that spins
horizontally with paddles extended from the spinning shaft (as shown).
4.2.2 GAS MIXERS
Gas mixers compress digester biogas and reintroduce the gas back into the
tank bottom through long, gas lance pipes where large bubbles agitate tank
contents on their way back up to the tank surface.
4.2.3 JET MIXERS
Jet mixers operate by pulling sludge from tank contents and reintroducing
the sludge at a high speed back into the tank by use of a motive pump to
move the tank's contents, frequently spinning contents in a circular pattern
through several jets nozzles.
Heating Coils - Internal to Tank (w/mixer)
Top Mounted Roof Mixer
Horizontal Mixer
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4.2.4 VERTICAL LINEAR MIXERS (VLM)
Vertical Linear Mixers operate by pushing and pulling reactor contents up
and down at a rapid frequency via a flat disk located deep inside the tank
held firm by a vertical shaft which is moved by a drive located at the top of
the tank. This offers the benefit of keeping all wear parts out of the digester
tank.
4.3 TANKS
Concrete is commonly used for digester tanks. Poured concrete can be
formed in a cylindrical tank shape or an egg tank shape using a network of
forms that shape the concrete and hold it in place for proper curing. Precast
concrete panels that are formed at an off-site factory can also be shipped by
truck to the project site where they are tipped up vertically and then tied together with a network of horizontal cable ties (see
picture). Concrete tanks will sometimes have a coating applied to the tank inner wall especially in the corrosive gas/water
interface zone to ensure long term durability.
Steel is also commonly used for digester tanks as well. Steel tanks can be erected either as bolted together panels or as welded
steel panels. Steel can either stainless steel or be coated with an epoxy paint system or with a glass-fused-to-steel coating.
Material selection is key so as to ensure long term durability and resistance to acid corrosion. Tanks are attached to the concrete
foundation by means of an embedded ring cast into the tank foundation. Access hatches are installed for access to the tank
interior.
Digester tanks are commonly insulated with either spray-on foam or rigid foam that is attached to the exterior tank surface.
Subsequent metal cladding, brick veneer, split block or other materials often attached to the foam's exterior for durability and
aesthetics.
4.4 CONVEYANCE (PUMPING)
Various types of pumps are successfully deployed at digester sites. Progressive cavity
pumps move very high solids streams using an internal impeller that looks like a
corkscrew and rotates in a way that pushes product along through process piping.
Piston style pumps move in a linear motion as an engine piston to convey very high
solids streams. Rotary lobe pumps utilize rubber or stainless steel lobes that spin in a
way that push against themselves and forces high solids material forward. Chopper
and grinder pumps are used in waste pits where significant trash and grit can
accumulate and can be tough to convey. Centrifugal pumps use a spinning impeller
to move material and are useful for liquid aqueous streams. Piping must be sized
large enough to prevent plugging.
Precast Panels in Place to Form 26 ft. tall Digester Tank
Lobe Pump Used for Slurries
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4.5 ROOFS & COVERS
4.5.1 FIXED & FLOATING
Many municipal digesters will commonly have a hard fastened roof on their
digesters with mixers hard mounted on the rooftop. Another common
digester roof, again found mostly in municipal settings is a metal roof
structure that floats on the digester contents and rides vertically on steel
guide members and roller mechanisms.
4.5.3 DUAL MEMBRANE
These covers have an outer membrane that spans the tank and is inflated by
a blower (see picture) and provides protection from severe weather and
odor containment. There is a separate, inner membrane that moves based
on the quantity of biogas stored under the outer cover as shown in the
cutaway picture.
4.5.4 GAS BLADDER HOLDERS
A soft double membrane inflatable cover that is mounted at grade and holds
enough gas volume to buffer swings in demand (see picture). The outer
membrane is inflated by an air compressor while the inner layer holds the
biogas. Inner pressure settings can be adjusted to user’s gas pressure
requirements.
Dual Membrane Cover at Merchant Site
Cutaway Sketch of Complete Mix Digester showing layering of membrane covers
Domed Gas Holder
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4.6 PROCESS CONTROL
A stable digester can bring years of steady performance. Unstable digesters, on the other hand, that have been overstressed can
lose their process biology and gas yield can suffer. Two common tests that an operator generally runs on the digester contents
are VFA (Volatile Fatty Acids) and Alkalinity. These tests are simple to run on the lab bench and the ratio of the two parameters to
each other show if the system is running in balance or is upset much like a person might experience as an upset stomach
reflecting too much digestive acids. Wastes that are deficient in alkalinity may require supplementation via the addition of lime
or caustic soda to buffer against the acids generated in the process.
4.7 PRETREATMENT
4.7.1 PASTEURIZATION
A mandatory feature for many digesters in Europe, pasteurization is only
now starting to take hold at some US facilities. Pasteurizers will commonly
heat batch volumes of feedstocks to roughly 70C for an hour to achieve virus
and pathogen kill. They commonly run as several parallel batch heating
tanks. In other places, pasteurization is accomplished at 50C for 24 hours.
4.7.2 FOOD WASTE PROCESSING
Food waste commonly needs to be ground up into a liquid pulp before being fed to the digester to expedite the digestion
process. Grinding is commonly done in chopper pumps, macerators, hammermills, and hydropulpers. Each of these works like a
big blender. Grit can be controlled with hydrocyclones that spin grit out of suspension. Depackaging technology is used in settings
where damaged or expired packaged food is a feedstock and works by first slicing or breaking open the package, spinning out
product contents and rejecting the package material into a separate rejects bin. Post-consumer food waste (green bin) is
notorious for having contamination which often needs to be pulled out ahead of the digester
4.7.3 MUNICIPAL
Advanced pretreatment systems are gaining popularity that break open cells in waste sludges to assist in getting the AD process
started. Thermal hydrolysis and cell lysing systems that use microwaves, electrical currents, and mechanical shearing are
beginning to show value.
Batch Pasteurizers in Parallel Operation
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5. DIGESTATE MANAGEMENT
The resulting liquid from a digester contains dissolved organic matter,
fibrous material, and nutrients. Digester operations that have ample land
nearby that can apply this fertilizer seasonally to crop lands that are looking
for nutrients. Fertilizers derived from AD system can provide results that are
equal to or better than comparable synthetic fertilizers. The form of
nutrients in digestate is readily plant available. Nitrogen is present as mostly
dissolved ammonia, phosphorous as phosphate and potassium in the ionic
form. Furthermore, the fertilizers add hums and microbes to the soils
improving plant productivity.
Many farm based digesters have sizable storage volume to hold this nutrient
rich liquid until their crops call for fertilizer. Digestate can be further
processed as outlined below based on particular site needs.
5.1 DEWATERING
Liquid digestate commonly leaves a digester with roughly 2-10% Total Solids and thus
90-98%% water. Common devices used to squeeze the water out of these solids are
screw presses, belt presses and centrifuges. Screw presses press the solids laden feed
liquid against a firm plate which squeezes the liquid out from the digestate. Belt presses
utilize permeable belts that sandwich the solids between rollers that squeeze the water
from the solids. Centrifuges have a spinning bowl at the heart of the process which,
through centrifugal action builds a sludge cake on the inner surface of the bowl as
material flows through with relatively clean water emerging at the outlet. These
technologies generate a solid digestate material that is about 15-30% solids and 70%-
85% water. Fiber and cellulose in the incoming feed can help make for a better quality
solid digestate product out the back end. An operating cost to be mindful of is polymer
chemicals that are deployed as dewatering aids.
An analysis from a Midwestern US food waste digester showed raw liquid digestate
constituents of 6.8% total solids, 7.1% Ammonia nitrogen, 0.8% total phosphorous, 0.8%
total potassium, as an example.
5.2 DRYING & PELLETIZING
For those applications, looking for a very dry solid product a thermal drying
step can be used. Systems like paddle dryers, direct fired dryers or infrared
dryers can generate a solid fertilizer of greater than 95% solid matter.
Pelletizers add an additional amount of solid particle recovery control
generating a hard, nutrient dense, dry fertilizer. Ideally, there would be
enough waste heat at the site to drive the dryers and avoid purchased gas
for drying purposes.
Screw Press at Dairy
Centrifuge at Dairy Digest Happy Farm
Digester User
Solid Digestate
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5.3 MANAGEMENT OF LIQUID FRACTION
The liquid fraction of dewatered digestate presents both opportunities and challenges. The ideal scenario is for liquid digestates
to be simply land applied. In those instances where logistics prevent direct land application, other options need to be evaluated
such as discharge to the local sewer (POTW) or to treat the water to stream discharge limits. Digestates can have nitrogen and
phosphorous levels that are considered elevated for discharge. Technologies for addressing elevated nutrients in liquid fraction
of digestates include:
5.3.1 ANAMMOX
A biological process that converts dissolved ammonia to nitrogen gas utilizing a specialized bacteria. Most applicable where
nitrogen levels are over 500 mg/l. Achieves about 85% efficiency.
5.3.2 MEMBRANE FILTRATION
Common membrane filters include ultrafiltration which removes suspended solids and longer molecules and reverse osmosis
which filters out virtually all molecules and ions from solution and allows only water to pass through. All membrane filters have a
reject stream that requires management, has significant electrical demand to drive the high pressure pumps and periodic
membrane cleaning and replacement. Membrane bioreactors (MBR) can be deployed to biologically treat the nutrients.
5.3.3 EVAPORATION
Using excess facility heat to drive an evaporator can be an effective way to reduce the volume of digestate and concentrate the
nutrients. Common evaporator types include scraped surface designs where a mechanical scraper is used to keep material from
caking onto the hot surfaces.
5.3.4 AIR STRIPPING
Ammonia can be stripped out of solution using stripping technology as it is often easily volatilized depending on its ionic state.
This is deployed usually in a tall, packed-tower design. Increasing pH of the digestate, warming the water and pulling a vacuum
on the water all enhance the system efficiency. Commonly stripped gasses will be scrubbed with a chemical such as sulfuric acid
so as to make a beneficial precipitate like ammonium sulfate fertilizer.
5.4.5 STRUVITE PRECIPITATION
Excess phosphorous in combination with magnesium and ammonium in the
digestate can precipitate with high efficiency. A molecular matrix molecule
known as struvite forms in the presence of a 1:1:1 ratio of magnesium,
nitrogen and phosphorous in the liquid. Struvite crystals can be stored,
bagged and shipped to users in need of the phosphorous. Struvite can pose
operational issues if allowed to build up in digester piping in an uncontrolled
fashion.
5.4 MANAGEMENT OF FINAL COMPOST
For some uses, solid digestate can be stable enough for immediate use. In other instances, the material is still biologically active
and can benefit from additional composting or curing. Solid digestate compost can have beneficial plant fertilizer properties as it
is loaded with organic matter and high quality nutrients.
Struvite Fertilizer from Digestate
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6. GAS UPGRADING & HANDLING
6.1 HYDROGEN SULFIDE H2S
Hydrogen sulfide is found in all biogas streams to a varying degree based on the type of
feedstocks. Depending on the application, H2S levels can range from under 100 ppm to over
several thousand ppm. Due to its corrosive and odorous properties, removing the H2S is
generally a requirement. Additionally, chemicals based on iron salt chemistry, such as Ferric
(or ferrous) Chloride, ferric hydroxide or iron oxide can be added to digesters where the iron
will stabilize (oxidize) the sulfur in the sludge.
Alternatively, Iron Sponge filters use an iron based media, often iron impregnated wood
chips, that oxidizes the iron to a type of rust particle and requires periodic chemical
regeneration (see picture). Biological treatment scrubbers utilize a specialized aerobic
bacteria (Thiobacillus) that is applied in an upflow packed tower configuration (see picture).
The biology reacts with the sulfur in the biogas to form low pH sulfuric acid which can add
beneficial sulfur to final digestate upon blending.
Water wash systems utilize a high pressure water scrubbing concept which
will dissolves the H2S into the liquid stream. There are also processes that
use proprietary iron oxide granular media or activated carbon media as an
adsorbent that are effective at removing H2S. An additional approach is to
manage the H2S inside the digester. As shown in the photograph below this
digester has wooden beams in the gas head space that exhibit properties
favorable to the growth of a bacteria that will oxidize the H2S right in the
reactor. Oxidized sulfur will periodically fall back down into the tank
contents. Other suppliers will furnish a fabric netting in the gas head space
that achieves a similar result. A small percentage of oxygen is sometimes
injected in the digester head space to oxidize H2S but must be controlled to
<1% oxygen levels for safety purposes.
Biological H2S Scrubber
Iron Sponge Filters
Concrete Digester tank showing Wood Planks for Desulfurization, Epoxy Paint for Corrosion Resistance, Center Pier Structure and Submersible Mixers
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6.2 SILOXANES
Siloxanes are a class of compounds used in cosmetics and other personal
care products. They often find their way into digesters and biogas at
municipal WWTP and landfill settings. Proper removal by carbon filtration or
specialized adsorbents is critical to avoid formation of silica scale on hot
surfaces in downstream energy generation (see picture). Once formed, this
silica scale can be extremely difficult to remove. Fine silica can cause
premature wear and erosion of turbine or engine components leading to
failure.
6.3 HUMIDITY
Digester gas is saturated with water vapor. This can cause rusting and
corrosion in gas piping and create problems with downstream combustion equipment. As the gas cools, its vapor forms liquid
condensate which can pool in low spots and can plug improperly designed piping. Creating condensate either via refrigeration,
desiccant drying or through a series of knock-out pots can bring the dew point of the gas down to manageable levels. Condensate
management through properly designed piping and dehumidification will prevent a number of possible operational problems.
Furthermore, gas piping needs to accommodate and remove possible digester foam that can occur during process upsets. Simply
running biogas piping underground in northern climates can be very effective at knocking out moisture.
6.4 CO2
Biogas commonly has 30-50% CO2. Some downstream applications such as vehicle fuel or gas pipeline injection require reducing
that concentration to <2% CO2. There is a wide variety of commonly deployed approaches to this objective.
6.4.1 MEMBRANES
In a membrane filter system, pretreated gas is compressed and fed into a network of
fibers that are about the width of a human hair and packed into a vessel with many
thousands of such strands. Due to their ionic properties, methane molecules are rejected
by the membrane and the CO2 filters through the membrane. This allows for both a
purified CO2 and purified methane stream to be produced.
6.4.2 AMINES
These scrubbers incorporate a chemical reaction between the CO2 and a class of nitrogen
based compounds called amines to cleanse the gas. During the process, the amine
reaction first selectively scrubs out the CO2 and shortly thereafter the process is reversed
and the CO2 is vented and the liquid amine chemicals are reused.
Siloxane Filters
Amine Scrubber
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6.4.3 WATER WASH
Water Wash technology incorporates chemical concepts commonly found in making carbonated
soft drinks. CO2 does not dissolve well in water at ambient pressures but will dissolve in water at an
elevated pressure. Just as CO2 degasses out of a carbonated soft drink after the pressure is released
by opening the package the same happens in a water wash scrubber where biogas is scrubbed in a
pressurized water spray and later released from solution after subsequent depressurization.
6.4.4 PSA
Pressure Swing Adsorption technology extracts CO2
from biogas using a special adsorbent media and
allows methane to pass through. Much like a
charcoal filter, PSA systems operate several vessels
in parallel where at any given time one will be
filtering the gas and the others will be regeneration
done by backpulsing the beds with air to strip out the
adsorbed CO2. End purity of 98%+ methane is
commonly achievable.
Water Wash System
700 CFM PSA Unit on Digester Gas
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7. GAS USE
7.1 CHP
Combined heat and power (CHP) is the most prevalent means of utilizing
biogas. These units use engines similar to those used in cars and trucks
where pistons pressurize the gas, combust it and turn a shaft which, in turn,
spins a generator. A hard-shell jacket surrounds the exterior of the engine
that uses a heat transfer fluid like water or glycol to capture the heat that
comes from the combustion happening in the engine. Depending on the
quality of the gas, regular oil changes are a regular, significant, maintenance
expense. A rule of thumb is that about 100 cubic feet per minute of biogas
can drive a 300-Kilowatt engine which is enough power for about 300 homes
(reference - Operating data from Gloversville Johnston, NY). Connecting the
electricity to the electrical grid can help local utilities meet their Renewable Portfolio Standards (RPS). The connection from
digester to power grid can sometimes be a complex process, as Utilities tend to closely scrutinize projects that provide power
onto their grid for ensuring grid integrity.
7.2 OTHER - MICROTURBINES & FUEL CELLS
These units require a higher feed pressure and higher feed gas quality than CHP engines but can provide decades of reliable
service and very high conversion efficiency.
7.3 VEHICLE FUEL
Once the gas has been upgraded and the CO2 removed, it is ready to be
compressed and used in vehicles. Compressed Natural Gas (CNG) is routinely
compressed to 2500 psi in high pressure cylinders to store the gas.
Compressing the gas reduces the volume by a factor of 200 vs atmospheric
gas. Upgraded biogas has about 950 Btu of energy in every cubic foot of gas.
Diesel fuel, on the other hand has about 140,000 Btu in a gallon. Gas units
are commonly referred to in units of GGE or Gallons of Gas Equivalent for
vehicle fuel projects. For example, the energy in 1000 cubic feet of upgraded
biogas equals about 7.2 Gallon of Gas Equivalent (GGE) as each of these
units has about 1 Million Btu's of energy. The illustration below compares
how the equivalent amount of energy varies by volume in different gas
forms and pressures.
500 KW CHP Engine
High Pressure Bio CNG Trailer for Vehicle Fueling
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Biogas used in vehicle fuels can be considered an "Advanced Biofuel" as spelled out in the Renewable Fuel Standard (RFS2). This
is monetized by selling credits that are tracked by Renewable Identification Numbers (RIN). Biogas is considered the lowest
carbon intensity fuel and can qualify for California's Low Carbon Fuel Standard.
7.4 DIRECT CONNECTION TO GAS GRID
Upgraded biogas can also be injected into the natural gas utility grid as long
as local regulations allow and the grid is in close enough in geographical
proximity. Currently there are no national standards for upgraded
biomethane, so target gas quality and injection pressure is a locally driven
issue dependent on pipeline operator. Common specifications to connect
to the grid will be Methane, Oxygen, Nitrogen, CO2 levels and dew point.
An interconnect agreement has to be secured with the local pipeline in
order to connect to the grid. Once the facility is connected to the grid, the
gas can be sold to any user that uses natural gas from the grid.
7.5 GAS SAFETY
Gas safety equipment must allow a digester to vent gas should system
pressure elevate. Vented gas should be sent to a flare. Pressure relief valves
must be properly designed, insulated and heated to ensure proper year
round operation. Burst discs, foam traps and flame arrestors round out the
safety equipment needed.
Gas Safety Device
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8. PROJECT DEVELOPMENT AND FINANCE
Securing financing for a digester project can be challenging and takes significant time and effort. Each project progresses based
on its individual merits of owner's personal or corporate equity position, credit record, management resume and the projected
financial payback for investors. Often grants such as the USDA REAP grant, and other Federal and State grants are an integral part
of the financial backbone of a project. AD projects can also obtain a number of tax credits that can be of great value to businesses
that have tax burdens. AD projects can involve a complex web of securing the site, site permits, feedstock input agreements,
Power Purchase Agreements (PPA), off take agreements for fertilizer byproducts, equity financing, debt financing, construction
period financing, selection of the operations and maintenance crew and grant funding. The number of moving parts to a
successful AD project deal going forward can be daunting but generally makes for a great story when all the parts fall into place.
Public Private Partnerships (P3) are gaining in popularity whereby private companies can bring financing to project at municipal
settings in exchange for a long term partnership.
9. DIGESTER CONSTRUCTION METHODOLOGY
There are a wide number of ways to contract to build a digester project. Some projects will follow an EPC path
(Engineer/Procure/Construct). In the EPC case the owner deals with one single entity for all issues pertaining to system design,
process performance and construction. An EPC provider will often bring in a digester process provider onto their team for a
system performance guarantee. Early stage project geotechnical report and soil borings are required to understand site
constructability. Some urban sites require environmental site assessments in case of previous site contamination.
Some owners will chose to split projects into multiple contracts where they will contract separately for system design, permitting,
construction and the process and power generation equipment. This can put a heavier management responsibility on the owner
but can allow for some additional financial transparency, flexibility and hardware choices. This can provide additional
transparency and flexibility at the 30% design stage when system design and costing gets tightened up. A Basis of Design (BOD)
report is a common early stage deliverable that includes general arrangement drawings, process flow diagrams, equipment lists,
electrical one-line diagrams and process & instrumentation diagrams (P&IDs). At all times local building and construction codes
need to be understood and adhered to.
Each of these models provides their own level of flexibility and accountability for all participants involved. Some key points
involve payment considerations assumption of process performance risk, schedule risk, site condition risk, power output risk and
construction risks.
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Submersible Mixer on Support
Pole
Digester with Center Pole Cover Support Gas Storage Dome Showing Inflation Hose
Side Mounted Digester Mixer and Tank View Port
Complete Mix Digester Tank Showing Freestanding Mixers, Wooden Desulfurizers and Center Pier Column
CSTR Complete Mix Digester, Inflatable Gas Storage and
Containerized CHP Units Submersible Mixers on a Freestanding Support Structure
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11. US PROJECT EXAMPLES
.
Magic Hat Brewery in S. Burlington, VT
Cayuga County, NY Soil and Water Conservation District
Synergy Digester -- Wyoming County, NY
Lawnhurst Dairy - Stanley, NY
Reduces byproduct management costs by over 60% through
cutting waste trucking and municipal surcharges. Reduces
odors; truck traffic; BOD and phosphorus loading to the
municipal treatment facility. Generates one-third of the
brewery’s electrical demand while nestled in a residential
neighborhood. Digests spent grains and wastewater.
Co-Digests imported food waste and dairy cow manure from
1500 milking cows. Generates 541 KW of electricity. $5M total
installed costs
Co-Digests imported food waste and dairy cow manure from
1200 Head Dairy. Makes 1.4 MW of electricity. $7.7 M total
Capex. Includes Pasteurization
Fed by manure from 1500 cows. Community digester sends
heat and electricity to nearby prison and senior housing
development. 633KW electrical generation capacity. Hydraulic
Digester Technology. Biodesulfurization
$9.7 M total installed cost
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GenEarth – Berkeley County, SC (Charleston area)
JC Biomethane - Junction City OR
Clear Horizons - Dane County, WI
University of WI - Osh Kosh
Receives liquid industrial and municipal residual wastes from
local community and generates 1.6 MW power. $12M total
installed cost. Capacity – 60,000 – 75,000 wet tons per year of
wastewater treatment plant residuals (biosolids), Food
Processing Wastes, Urban GTW/FOG. Pasteurization for
achieving digestate/biosolids “unrestricted use” designation
under EPA 503 Class A biosolids. Start-up – Dec 2012
Receives preconsumer food waste, grasses. 1.6 MW of
electricity. 30,000 tons per year. Entec Technology – Wet
Digester CSTR. Design, build, own, operate, and maintain. 100
tons per day or about 30,000 TPY of commercial organics (post
consumer food waste), fats/oils/greases, and some agriculture
residues (manure and straw).
Cow manure from two large dairy farms conveyed by pipeline.
Community digester. $8M installed cost. Three large, complete
mix digester tanks.
Four fermentation vessels (70 ft. x 23 ft. x 17 ft. High), Runs as a
"dry" batch process that lasts one month for each cycle. Treats
8000 tons per year of food waste, yard wastes and crop wastes.
Biogas fires a 350 KW electrical generator
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Processes 40,000 tons per year of mixed food and yard waste from the
Metro Vancouver region (population 2.5 million). The batch two-stage high
solids anaerobic digester produces 2.2 MW combined heat-and-power and
15,000 metric tons of high quality compost hat is returned to local farms and
landscapes. Virtual tour at harvestpower.com/energygarden
Co-digests 120,000 tons per year of commercial food waste and biosolids
from local theme parks and businesses. The facility produces 6 MW
combined heat and power -- enough to power 2,000 Floridian homes -- and
3,200 metric tons per year of granular fertilizer for application on local
agriculture.
Uses low-solids anaerobic digestion to process 70,000 tons per year of
commercial food waste, producing 5.6 MW combined heat and power and
5,200 metric tons of granular fertilizer each year.
PSA unit from Guild. 385 cubic feet per minute free rate. Generates pipeline
quality gas of 98% methane.
Harvest Energy Garden - Richmond, BC
Harvest Energy Garden - Orlando, FL
Harvest Energy Garden - London ON
Biogas Upgrading System at GA Lagoon Based Digester
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SAMPLE LIST OF SIGNIFICANT MERCHANT FOOD WASTE DIGESTERS IN THE US
Name / Developer Location
Feed
(wet tpy)
Power
(KW)/ GGE
Harvest Power Orlando, FL 120,000 3.2 MW
Novi Energy Freemont, MI 100,000 3 MW
FCPC Renewable Gen Milwaukee, WI 100,000 2 MW
Zero Waste
(dry system)
San Jose, CA 90,000 1.6 MW
GenEarth Sumter, SC 70,000 1.6 MW
quasar Columbus OH 43,000 1.3 MW
JC Biomethane Eugene, OR 30,000 1.6 MW
Clean World Partners/ U C
Davis
Sacramento, CA 20,000 450 GGE vehicle fuel
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12. APPENDIX
TERMINOLOGY:
CSTR Completely Stirred Tank Reactor. Also known as a "wet" style digester
Feedstocks Any material including organics mixed wastes that are fed into a digester
Offtaker An entity that is buying fuels or fertilizer byproducts from a digestion facility.
Post-Consumer Waste Material collected from food plates from restaurants or cafeterias or home kitchen preparation
Preconsumer Waste Waste from food factories, grocery retailers
SSO Source Separated Organics - The system by which organic waste generators such as homes and
businesses segregate organic materials from other waste streams at the point of collection.
Substrates Term used interchangeably with "Feedstock"
Volatile Solids The fraction of the feed solids that is readily convertible to biogas. The opposite is the nonvolatile or
ash fraction.
FREE ANAEROBIC DIGESTION BIOGAS MODELS:
Anaerobic Digestion CREST Model
Biowatts
Energy 4 Farms
Additional Resources:
EPA Agstar
BioCycle Magazine
American Biogas Council
Digester.com - Industry blog & podcast
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ABOUT THE AUTHOR
Paul Greene is a Vice President with Natural Systems Utilities a project development company dedicated to building anaerobic
digestion infrastructure and Founding member of the American Biogas Council (ABC). NSU features its Community CoDigestion
Service Offering that builds, owns operates and finances AD facilities in community settings. He is a former Chairman of the ABC.
He can be reached at 518-951-5766 and pgreene@naturalsystemsutilities.com.
ACKNOWLEDGEMENTS
Amber Blythe BioFerm Energy Systems
Blake Sturke Turning Earth, LLC
Derek Hundert, Vicki Elliott PlanET Biogas Solutions
Earl Brubacher Bio-En Systems
Eric Fitch Purpose Energy
George Bevington Gloversville Johnstown Joint Water Treatment Facility
Meredith Sorensen Harvest Power
Michael Mataritan Guild Associates, Inc.
Patrick Johnson Sattler
Sara Martin O'Brien & Gere
Sherry Heinly KSB Mixing
Surya Pidaparti Novus Energy
Tom Lawson Envitec Biogas
Any suggestions on contents can be forwarded to pgreene@naturalsystemsutilities.com.