We use food waste (spoiled grain ,overripe fuits , kitchen waste etc) and agricultural waste in place of low calorie inputs like cattle dung or animal waste to make highly efficient biogas Just 2-3 kg of such feedstock produces about 450-600 g of methane, and the process is completed with in 48-72 hours. The conventional biogas systems, using cattle dung, sewerage, etc. use about 35-50 kg feedstock to produce the same quantity of methane, and require about 40 days to complete the reaction. Thus, from the point of view of conversion of feedstock into methane, the system developed is more efficient than conventional system.
Conventional Biogas new Biogas system
required feedstock : 35-50 kg + 45 lit water 2-3 kg + 15 litwater
Nature of required feedstock: Dung Any starchy material
Processing Time : 40 days 48-72 hours
Standard size for household: 4000 lit 1000-1500 lit
Producing biogas from treating organic wastes such as food waste or other agricultural waste can provide us with acceptable amount of energy and also a high quality fertilizer . Biogas is not just for agricultural wastes but also for industrial.
Anaerobic digestion is a proven technology and is widely used for recycling and treating wet organic waste and waste waters. It is a type of fermentation that converts organic material into biogas, which mainly consists of methane (approximately 60%) and carbon dioxide (approximately 40%).
Sources for producing biogas
- Food residuals
- Animal manure
- Energy crops
- Algal biomass
- Crop residue
- Sewage sludge
- Grass clippings/garden waste
Biogas can be used in both spark ignition and compression ignition engines
Biogas will not self-ignite in a diesel engine. Therefore, it is necessary to use a little diesel (approximately 16-18 per cent) to ignite the fuel. The biogas enters the engine via the air inlet system, after the air filter. This needs a small modification to the air intake system . This option also allows for the engine to be operated on diesel fuel alone in periods when there is insufficient biogas.
An engine requires 0.6- 0.7m3 of biogas/kWh.
SI engine was modified to power a water pump for irrigation by using 100% biogas as fuel (gasoline starting). A gas mixing device was designed to meter biogas into air stream of amount dictated by the engine speed and the load to obtain a proper proportion of biogas and air that burn for SI engine operation
§ The injection of a small amount of oxygen (air) into the headspace of the storage fermenter leads to oxidation of H2S by microorganisms and hence the elimination of a considerable part of the sulphur from the gaseous phase. This is the most frequently used method for desulphurisation. It is cheap and can eliminate up to 95% of the sulphur content in the biogas.
§ Another option is external chemical treatment in a filter. The active material may be:
§ 1.Iron-hydroxide: Fe (OH)2 + H2S -> FeS + 2 H2O. This process is reversible and the filter can be regenerated by adding oxygen. Adsorption material may be iron-rich soils, waste material from steel or aluminium production;
§ 2. By Activated carbon.
Other uses of biogas
Application
1 m3 biogas equivalent
Lighting
equal to 60 -100 watt bulb for 6 hours
Cooking
can cook 3 meals for a family of 5 - 6
Fuel replacement
0.7 kg of petrol
Shaft power
can run a one horse power motor for 2 hours
Electricity generation
can generate 1.25 kilowatt hours of electricity
· the waste is reduced to slurry which has a high nutrient content which makes an ideal fertiliser
cost
as I describe above that biogas can be use in conventional diesel or gasoline pump which are available at very low costs and the cost for building food waste biogas plant is also very low because it requires less feedstock than conventional biogas system .so this is the cheapest system for farmers of bihar.
