Energy from Biomass is one of the most widely used options. With the availability of new technologies there are various means to convert biomass into energy efficiently.
The biogas yield from Gobar or cow dung is very low as compared to various other biomass, therefore there is a need to design biogas plants for digestion of other efficient material. The widely available vegetative biomass (usually weeds) and Kitchen waste form the important material for designing efficient biogas models. At the same time not compromising on food security issues, developing countries could also take up Energy Farming (Production of biomass on fields for energy utilization - beside food production and organic waste utilization). Anaerobic digestion and gasification technology are possibilities for Energy Farming.
I have developed a prototype mini-biogas plant called 'SRUSHTI' means creation. This model works with vegetative biomass (grass, leaves) and kitchen waste as raw material. It was created last year. This requires 2 kilograms of Kitchen waste and other green matter as feed, and releases about 2 cubic meters of biogas. Initially to activate dung of cattle should be added for introducing methane generating bacteria.
The challenge was to develop a very low cost and efficient bio-gas plant, for communities to adopt with out subsidy. This prototype was costing about Rs. 3,500/- or about $80 (USD).
The yield of biogas increases in this order for same quantity by weight of the raw material as it is : cowdung, pig litter, vegetable, poultry litter, bush waste, sewage, food waste, grass and vegetable oil. As compared to the lowest and the maximum the difference is at least 5 to 10 times.
Digester: A GI sheet drum as digester, an inlet (feed) and an outlet (digested slurry) system.
Controlling the temperature of the digester: Regarding keeping the temperature of the microbes at 37 degree centrigrade there are three options. The other option is to heat water through a simple solar water heater and circulate the water in the drum through copper tubes used for air conditioners which is adopted in this design.
Mixing the biomass: At the top of the drum a stirrer with handle arrangement is made, for rotating the material inside the drum. The shaft of the stirrer should be gas leak proof. Another traditional method is to rotate the floating drum.
Storing the gas: The gas is first stored in the floating drum and also in the extra plastic drum linked.I am keeping it under 'Open Source Technology' - any one could use the design as it is or modify for community and common good.
Requesting for suggestions to improve.