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9. BIOMASS ENERGYTopics: Biomass types, Characterization, Conversion routes, Bio chemical
BIOMASS Biomass is biological/organic material derived from living, or recently living organisms. (The term is equally applicable to both animal and vegetable derived material, but in the context of energy, it refers to plant based material) Renewable energy source Stored in form of complex organic compounds of Carbon, Hydrogen, Oxygen and Nitrogen etc. It is a source of ‘5F’: food, fodder, fuel, fiber and fertilizer. It can be converted into useful forms of energy through different conversion routes. Gets converted into fossil fuels after several million years under certain conditions of pressure, temperature, air etc. fossil fuels are not renewable, hence, are not biomass.
EXAMPLES OF BIOMASS Wood: Trees, bushes, wood residue (Sawdust, bark etc. from forest clearings and mills) Wastes: Municipal Solid Waste (Paper, food and yard wastes, plastics, wood and tires), Livestock Waste, Process Waste, Sewage Crops: Starch crops (Corn, wheat and barley), Sugar crops (Cane and beet), Forage crops (Grasses, alfalfa, and clover), Oilseed crops (soybean, sunflower, safflower ) Aquatic Plants: Algae, Water weed, Water hyacinth, Reed and rushes
BIOMASS AND CARBON EMMISIONS Living biomass in plants and trees absorbs carbon dioxide from the atmosphere through photosynthesis Biomass emits carbon dioxide when it naturally decays and when it is used as an energy source Biomass causes a closed cycle with no net emissions of greenhouse gases
BIOMASS ENERGY Energy obtained from biomass is called biomass energy. Produced by green plants through photosynthesis in presence of sun light Sunlight 6CO2 + 6H2O (CH2O)6 + 6O2 + 636 kCal Chlorophyll t (biomass) Other living organisms consume green plants or their byproduct and generate biomass
ORIGIN OF BIOMASS ENERGY
BIO-FUEL Derived from biological carbon fixation of biomass Examples are Bioalcohols Biodiesel Green diesel Biogas Solid bio-fuels
BIO-FUEL (contd…) Bioalcohols Produced by the action of microorganisms and enzymes through the fermentation of sugars or starches or cellulose Biodiesel Produced from oils or fats using transesterification Green diesel Produced from traditional fractional distillation to process the oils of canola, algae, jatropha and salicornia
BIO-FUEL (contd…) Biogas Produced by the process of anaerobic digestion of biodegradable waste materials or energy crops The solid byproduct can be used as a biofuel or a fertilizer. Solid biofuels Raw biomass is burnt directly in a stove or furnace to provide heat Loose biomass (saw dust, rice husk) is densified by palletization/briquetting.
BIOMASS ENERGY RESOURCE The raw biomass for extracting secondary energy (fuel, organic chemicals, etc.) is called biomass energy resources. Biomass Energy Resource are broadly classified into two categories: Nurtured/Cultivated: Biomass from cultivated fields, crops, forests and harvested periodically, aquatic/marine plants. Waste Organic Material: Biomass from waste e.g. municipal waste, animal excreta/dung, forest waste, agricultural waste, bioprocess waste, Industrial waste, butchery waste, fishery wastes, processing waste etc.
PRINCIPAL BIOMASS ENERGY RESOURCES AND CONVERSION PROCESS Category Name of the Conversion Process Biomass Source Cultivated Trees, (Wood chips, Burning to produce heat Energy saw dusts) and electricity Resource Aquatic crops, Producing biogas and algae, green plants biochemicals Agricultural crops Production of gas (Wood gasification) Fruit farms Production of wood oil and charcoal (Wood to oil process)
PRINCIPAL BIOMASS ENERGY RESOURCES AND CONVERSION PROCESS (contd…) Category Name of the Biomass Source Conversion Process Waste – Rice and wheat husk Production of Biomass Baggase of sugar cane ethyl alcohol resources by Coconut husk, groundnut shell, straw from fermentation of rice, wheat etc. farms and of molasses, bio- Waste of furniture industry, wood beet root, industry industry fruits, Waste of poultry industry, fishery potatoes, industry, food industry, brewery, cereals tannery, butchery etc. Carbohydrates, glucose, fructose etc.
ADVANTAGES OF BIOMASS ENERGY Renewable and inexhaustible (theoretically) source of energy Biomass is very abundant. It is easy to convert to a high energy portable fuel such as alcohol or gas which are efficient, viable and relatively clean-burning. It is cheap in contrast to the other energy sources. Biomass production can often mean the restoration of waste land (e.g. deforested areas) Commercial use of biomass may reduce the problem of waste disposal
ADVANTAGES OF BIOMASS ENERGY (contd…) It may also use areas of unused agricultural land and provide jobs in rural communities. When direct combustion of plant mass is not used to generate energy (i.e. fermentation, pyrolysis, etc. are used instead), there is minimal environmental impact If it is produced on a renewable basis using biomass energy, it does not result in a net carbon dioxide increase as plants absorb it when they grow. Nitrogen-rich bio-digested residue from a biogas plant is a good soil conditioner and improves the fertility of soil
DISADVANTAGES OF BIOMASS ENERGY A dispersed and land-intensive source Low energy density Could contribute a great deal to global warming and particulate pollution if directly burned Still an expensive source, both in terms of producing the biomass and converting it to alcohols On a small scale there is most likely a net loss of energy- energy must be put in to grow the plant mass
SCOPE OF BIOMASS ENERGY Scope of biomass energy Rural applications of biomass energy. Urban and industrial applications of biomass energy. Biomass as a primary source for large scale electrical power generation. India has vast land based, aquatic, forest, agricultural biomass resources. Biomass energy processes serve many purposes: Energy supply: Fuel, biogas, Organic chemicals Rural development Waste disposal Environment balance
ENERGY PLANTATIONS (TERRESTRIAL) Growing of selected species of tree and plants on a short rotation basis on waste or arable land for energy generation point of view e.g. Acacia nilotica (Babul, grows even in wasteland) Dalbergia Sissoo (Sheesham, high calorific value up to 4900 kcal/kg) Prosopis Juliflora (Vilayati Babul, Root up to 50m) Albizzia Lebbeck (Siris)
ENERGY PLANTATIONS (AQUATIC) Growing of floating water plants e.g., water hyacinth in rivers, lakes, ponds etc in tropical / sub-tropical area (yield 25 T(dry)/ha/yr)
BIOMASS FROM WATER BODIES Algae biomass is an important renewable source of energy produced by photosynthesis.
BIOMASS FROM WATER BODIES (contd…) The algae is produced in algae farms. Algae contains organic matter which can be converted into methane gas (a useful fuel) in a simple biogas plant by the process called anaerobic digestion. Algae crops are likely to be cultivated on large scale to obtain renewable energy. After extracting the biogas, the organic residue from the biogas-plant is added to the algae pond. This acts as a food to the bacteria in algae pond. The algae-bacterial combination consumes the waste organic water in the pond, absorbs solar energy and results in rapid growth of algae.
BIOMASS ENERGY CONVERSION PROCESSES The biomass can be converted to useful energy forms such as: Heat Gaseous, Liquid and Solid fuels Organic chemical The biomass conversion process has several routes depending upon temperature, pressure, micro- organisms, and process conditions. These routes are classified in following three broad categories. Direct combustion (Incineration) Thermo-chemical conversion Biochemical conversion
BIOMASS ENERGY CONVERSION PROCESSES AND END PRODUCTS Conversion Biomass Resource Products Market ProcessSolid biomass (Wood, Combustion Heat Heat/CHP, ElectricityStem) Pyrolysis Bio oil, Fuel gas Transportation fuel Gasification Fuel gas Transportation fuelWet biomass Anerobic Biogas Electricity(Organic waste, digestionManure)Sugars and starch Hydrolysis and Bio-ethanol Transportation fuel,Plants (Sugarcane, Fermentation Chemicalbeet, cereals)Oil crops (rapeseed, Extraction and Bio-diesel Transportation fuelsunflower) Esterification
DIRECT COMBUSTION Direct combustion (rapid oxidation accompanied by heat and light) of biomass is the most straightforward method of energy production. Generally direct combustion is applicable to solid biomass including cultivated biomass and waste biomass. The heat released by direct combustion can be used for several useful purposes such as cooking, industrial heat, steam generation etc. The direct burning of biomass is the cause of a great deal of pollution and has contributed to global warming. Incineration is the process of burning completely to ashes. The heat generated is either used to generate electricity or to provide heat for industrial purposes and space heating
DISPOSAL OF PADDY STRAW
SATELLITE PHOTOGRAPH ON GOOGLEEARTH SNAPSHOT OF NORTHERN INDIA November 4, 2008 Source: Earth Observatory (NASA) Smoke due to improper combustion (Damage to environment and loss of huge source of energy)
A TYPICAL POWER-PLANT An electrostatic precipitator (ESP) controls particulate emissions Only Boiler & ESP needs to be redesigned
BIO-MASS STORAGE METHODS SILAGE PILING
BIO-MASS STORAGE METHODS (contd…) EURO BAGGING
THERMO-CHEMICAL CONVERSION Biomass is converted into another chemical form by thermo- chemical processes in which heat is the dominant mechanism. These processes include gasification and pyrolysis and are separated principally by the availability of oxygen and conversion temperature. Gasification is the conversion of a solid biomass into a gaseous fuel at a high temperature with controlled air. Pyrolyisis involves the heating of biomass such as wood or agricultural waste at around 500-900 oC in the absence of oxygen to decompose it into gas and charcoal (carbon). A major advantage of pyrolysis is that carbon dioxide, one of the main drawbacks to most biomass energy conversion processes, is not produced. A disadvantage, however, is that the biomass must be heated to relatively high temperatures, a process that itself requires significant amounts of energy.
BIO-CHEMICAL CONVERSION The process makes use of the enzymes of bacteria and other micro-organisms to break down biomass to produce liquid and gaseous fuels In most cases micro-organisms are used to perform the conversion process: anaerobic digestion, fermentation and composting. Other chemical processes such as converting vegetable or animal oils into biodiesel is transesterification.
ANAEROBIC DIGESTION Biological treatment can be done either in presence of oxygen (aerobic) or in absence of oxygen (anaerobic). In India, anaerobic digestion plants are commonly known as Biogas Plants or Gobar Gas Plants. In such plants slurry of cow dung and water is fed to the digester and is allowed to ferment for a few weeks. The biogas is released. The biogas contains about 55% of methane (CH4). This gas is used as a fuel. There are two types of Biogas Plants Fixed head Floating head
ENERGY ROUTE OF BIOGAS
TYPICAL BIOGAS COMPOSITION Sl. No. Constituents % (V/V) 1 CH4 60 2 CO2 38 3 H2S <1 4 H2O vapors ~1 Heating value = 4500 – 4700 k cal/m3
SCHEMATIC OF A FIXED DOME TYPE BIOGAS PLANT
SCHEMATIC OF A FLOATING DOME TYPE BIOGAS PLANTPosition a of dome with less gas in the dome. Position b of dome with more gas in the dome.
COMPARISON OF FIXED AND FLOATING HEAD BIOGAS PLANT Janta/Fixed dome type Floating Dome type Biogas Plant1 Gas is released at variable pressure Gas is released at constant pressure2 Identifying defects is difficult Identifying the defects in gas holder easy3 Cost of maintenance is low Cost of maintenance is high4 Capital cost is low Capital cost is high (for same capacity)5 Space above the drum can be used Floating drum does not allow the use of space for other purpose6 Temperature is high during winter Temperature is low during winter7 Life span is comparatively longer Life is short8 Requires move excavation work Requires relatively less excavation
SIZES OF BIOGAS PLANTS Biogas Size of Category Application Delivery DigesterVery small 0.65 - For small family of 3Biogas plant m3/day members having 2 cattle.Small biogas 2 m3/day - For family of 6 membersplant having 8 cattle.Medium (family 3 m3/day 1.6 m dia, For family of 12 personssize) biogas 4.2 m height having 12 heads ofplant cattle.Large (farm 6 m3/day 3.3 m dia, For a farm having poultrysize) biogas 4.65 m height diary etc., 20 cattle.plantVery Large 2600 1000 m3 Cattle 1000(community m3/daysize) (CO2 free)
ADVANTAGES AND DISADVANTAGES OF FLOATING DOME DESIGN Advantages Disadvantages• The slurry is constantly • Higher cost due to fabricated submerged below the dome. dome construction.• The pressure is naturally • Dome upper surface is exposed equalised. to sunlight and external• No danger of excessive pressure. atmosphere. The heat is lost• No danger of mixing between during winters. biogas and external air. Hence no • The outlet pipe between the danger of explosion. floating dome and fixed external• Gas is obtained at uniform and connection should be of flexible constant pressure. hose type. It is subjected to sun• Gas does not leak through the rays, rain and movement. It dome as the slurry provides needs regular attention and natural screen. maintenance.
LARGE BIOGAS PLANT AT VIJAYAVADA MUNICIPAL CORPORATION
TYPICAL GAS PRODUCTION FROM DIFFERENT FEEDSTOCK Sl. Typical Gas Yield Typical Methane Content Feedstock No. (liters/kg) (%) 1. Paper Waste 480 53 2. Bagass 330 57 3. Spent Tea Waste 235 57 4. Food Waste 160 62 5. Bamboo Pulp 145 54 6. Dry Leaves 118 60 7. Green leaves & twigs 100 65 8. Fruit waste 91 50 9. Bamboo dust 53 72 10. Distillery effluent 31 75 11. Black liquor (Paper Mill) 22 69 12. Animal Excreta - Cow/Bullock 36 60-65% - Buffalo 36 “ - Pig 78 “ - Chicken 62 “ 13. Human Excreta 70 “
FERMENTATION Process of production of ethyl alcohol from any feedstock containing sugar or starch or also from cellulose materials. Feedstock: Sugar: Sugar beets, sugar cane, sweet sorghum, Fruits etc Starches: Grains like corn, wheat, potatoes etc. Cellulose: Wood, solid waste, agricultural wastes etc. Process of production: Fermentation of fermentable sugar solution Fermentation of sugar solution to Ethyl alcohol Separation of ethanol from other by – products.
PROCESS OF PRODUCTION OF FUEL ALCOHOL Feedstock Milling Sterilization Cooking (enzymes & water added to form mess) Cooling Fermentation (yeasts addition) (2 days) Bear (10% ethyl alcohol) Distillation Dehydration Denaturation Fuel alcohol