More Related Content
Similar to BIOENERGY PRODUCTION UTILIZING WASTEWATER IN REMOTE LOW-TEMPERATURE ALASKA
Similar to BIOENERGY PRODUCTION UTILIZING WASTEWATER IN REMOTE LOW-TEMPERATURE ALASKA (20)
Recently uploaded
Recently uploaded (20)
BIOENERGY PRODUCTION UTILIZING WASTEWATER IN REMOTE LOW-TEMPERATURE ALASKA
- 1. BIOENERGY PRODUCTION UTILIZING WASTEWATER IN REMOTE LOW- TEMPERATURE ALASKA CASEY BALLARD, CARLY FITZ MORRIS, ALEXANDER KASKO, JOHN THOMAS LENCKE, ANDREW LIN CLEMSON UNIVERSITY, CLEMSON, SC NOVEMBER 1ST, 2022
- 2. OUTLINE ● INTRODUCTION ○ BACKGROUND ○ RATIONALE ○ OBJECTIVES ○ APPROACHES ● LITERATURE REVIEW ● MATERIALS AND METHODS ● RESULTS ● CONCLUSION ● ACKNOWLEDGEMENTS
- 3. INTRODUCTION
- 4. BACKGROUND ● Alaskan temperatures lead to near year-round permafrost ● Communities are extremely remote due to Alaska’s size ● Modern plumbing appliances are infeasible if not possible ● Solution for human waste is a “honey bucket” paired with intermittent lagoon delivery ● Alaskans input their waste in a plastic bag in the honey bucket, tie up the waste, and discard in a lagoon ● Lagoons are sometimes far away and travel is difficult due to dirt roads and poor maintenance conditions
- 6. RATIONALE ● Rural Alaskans living in freezing temperatures reaching -20°C during the winter are without modern plumbing and waste disposal facilities ● By utilizing human waste through collection and anaerobic digestion, a sustainable source of heat in the form of biogas will improve the health and living conditions for many Alaskans
- 7. Goal The goal of this project is to design a waste management system to produce bioenergy for rural Alaskans by incorporating anaerobic digestion of human waste.
- 8. OBJECTIVES The specific objectives of this project are: 1. To design a collective waste system 2. To design a bioreactor 3. To store, transport, and utilize methane
- 9. Design a Collective Waste System ● TASK 1: To devise a structure that can store a community-wide amount of waste for up to an extended period of time ● TASK 2: To design a system for easy-access waste entry to the digester ● TASK 3: To incorporate an effluent removal system for cleaning
- 10. Design a Bioreactor ● TASK 1: To construct a psychrophilic batch reactor to produce methane from community waste ● TASK 2: To evaluate the amount of insulation needed to keep the bioreactor operating at 20℃ ● TASK 3: To determine the microorganisms required to allow for anaerobic digestion to occur
- 11. Store, Transport, and Utilize Methane ● TASK 1: To design a safe mechanism to collect methane gas to be used for bioenergy production ● TASK 2: To determine a safe handling method to store methane ● TASK 3: To engineer a process for the methane collected to be used as heat by the community
- 14. Waste Collection and Storage ● 2,000 gallon tanks ○ Each tank can hold waste for an estimated 40 days for a population size of 100 ○ Estimate each person produces 0.4 gallons of waste each day ○ 2,000 - 400 gallons (the amount of volume left at top of tank for gas) = 1,600 gallons ○ 1,600 / (0.4 *100) = 40 days ○ 40 days of fermentation is also enough time for the reactions to take place and methane to be produced ● Current AutoCAD drawing is based off of AutoCAD dimension from Snyder Industries Inc. ○ Chose this design based off of its ability for easy installation and meeting all sizing and pricing criteria
- 15. Operating Conditions of Digesters ● Upflow Anaerobic Sludge Blanket ○ Requires constant pumping ○ Usually seen with higher temperatures ● Mixed Anaerobic Digester ○ Considered mixing method - Pumping settled substrate upward ○ Mixing allows for simpler modeling method ● Flow Conditions ○ Intermittent inflow will be assumed do to practices of Alaskans ● Operating Times ○ It is assumed that anaerobic conditions will soon occur in digester ○ Each digester will be filled for 40 days then closed ○ Determined by internal temperatures
- 16. Operating Conditions of Influent ● Fecal Waste ○ Complex mix dependent upon diet ■ Carbohydrates, fats, proteins, and fibers ○ Various methods of quantifying substrate ■ BOD, COD, VSS, TSS, ODM ■ Wet Mass will be used ○ About 0.4 kg wet mass expected per person per day ● Urine ○ High in nitrogen concentration ○ Accumulation of ammonia is a inhibitor yet to be modelled ○ Urine considered for volume addition to digester ○ About 1 kg wet mass expected per person per day
- 17. Metabolism of Substrate ● Hydrolysis is the rate limiting step ○ The remaining steps are relatively spontaneous ● Environmental conditions for remaining steps have yet to be considered
- 18. Biogas Production ● Product Formation as a function of influent mass ○ Often considered as total output for set input, not kinetically ● Kinetic biogas production ○ Total methane production as a function of hydrolysis rate constant has been used when hydrolysis is rate limiting
- 19. On-Site Temperatures ● EPA representative Dr. Max Krause has shared temperature data collected from Fairbanks, Alaska over the past 14 years ● Temperatures range from -26°C (-15°F) to 22°C (70°F) ● Shows very cold temperatures will need to be accounted for in methane production ● Psychrophilic bacteria need to be kept between 0-30°C ● Digester heat generation is negligible, so an external source of heat will need to be applied
- 20. Bioreactor Heating ● A cattle water heater was chosen to heat the digesters ● Commonly used to heat large tanks of water for cattle consumption during the winter ● The anaerobic digesters are comparable to cattle water tanks due to their large water volumes ● Designed to heat the water automatically when below a certain temperature, making sure the reactor cannot freeze during operation ● Will not melt the reactors because they are designed for use in rubber, plastic, and steel tanks
- 21. Reactor Mixing ● A centrifugal pump was chosen to allow for mixing inside anaerobic digester ● Generally used to pump diverse ranges of head and capacity while outputting an adequate flow rate ○ Water, organic matter, oils, and sewage ● Centrifugal pump will allow for any settled solids to be mixed properly
- 22. Energy Generation ● On-site data collected by Dr. Max Krause shows reliable solar radiation values in Fairbanks, Alaska ● Solar panels were chosen as the main source of energy for the system ● Common uses of solar panels include electricity, heating and cooling, charging, and many more applications ● Solar panels allow for an economically sustainable energy source in remote areas
- 23. MATERIALS AND METHODS ● Bioreactor Design and Modeling ● Methane Production Modeling ● Reactor Heating Modeling ● Solar Power Generation
- 24. Bioreactor Design and Modeling ● The general design for the bioreactor consists of two anaerobic digesters and a composting tank. All of which is surrounded by a layer of insulation ● Additionally, within the anaerobic digesters a pump will continually mix the waste ● AutoCAD was chosen to model the design for a couple of reasons ○ AutoCAD is a modelling software used to create precise 2D and 3D drawings and models. ○ AutoCAD is easy to use and has multiple benefits including decreasing errors, better quality, and creating an ease of understanding. Governing Equations Volume = πr2h
- 25. Methane Production Modeling Using STELLA ● It was decided a semi-CSTR model would serve as an acceptable model for methane production and waste utilization. ● STELLA was chosen for a couple of reasons ○ STELLA is a modelling software used for time dependent processes. ○ STELLA is intuitive to use and is quickly adjustable for different inputs (e.g. number of persons, waste composition, temperatures) Governing Equations Retention Time = Volume/Flow Hydrolysis Rate = kh*S Biogas = (YP/S)*(1-EXP(-kh*t))*S
- 26. Heat Modeling Using COMSOL ● Sub-zero temperatures are very common in Alaska, so they needed to be accounted for in the design ● Heat modeling was done using COMSOL, a modeling software used to simulate multiple physics in a system ● Useful for changing variables to show a range of scenarios ● A COMSOL model was used to simulate different weather throughout the year and justify the use of heaters to keep the reactor running at a psychrophilic state ● COMSOL provided the ability to simulate the coldest weather conditions in Alaska to make sure the reactor would only freeze during the winter, when the system cannot be filled Heat Transfer Equations: qo= h · (Text-T) Qo = P/V = Q ⍴Cpu ·⛛T+⛛· q = Q + Qted
- 27. Solar Power Generation Calculations ● Monthly Solar Energy Output Formula ● E = A ⨉ r ⨉ H ⨉ PR (Bureau, 2016) ○ E = Energy [kWh] ○ A = Area [m2] ○ r = Solar Yield [%] ○ H = Monthly Solar Radiation [kWh/m2/month] ○ PR = Performance Ratio ● Calculations based on Dr. Krause solar radiation values for one 140 W Output Solar Panel
- 28. RESULTS
- 30. Bioreactor Heating Cold (-26°C) Average (0°C) Hot (22°C)
- 31. Bioreactor Heating ● These monthly temperatures give us the baseline for determining the months of operation for our reactor ● For the reactor to stay above 0°C at its coldest point, the outside temperature must be above - 13.5°C, which starts during March and ends during November ● This ensures that the digesters can operate at a minimum time of six months as long as the residents can make it to the site ● During months of operation, the reactor can be kept at an optimum temperature of 12°C
- 34. Going Forward
- 35. Project Flowchart ● Project Start/Background ● Research and waste collection design ● Bioreactor design and modeling ● Methane Utilization ● Design Finalization/Reflections ● End of project/Present
- 36. Gantt Chart
- 37. Acknowledgements We would like to acknowledge and thank Dr. Darnault, Dr. Max Krause, Dr. Dodd, Dr. Drapcho, Jeannie Williamson, and the Biosystems Engineering Department for their help in completing this project for Senior Capstone Design.
- 40. THANK YOU