how to make bio gas small plant
Biogas
Welcome to the "Beginners Guide to Biogas".
Biogas can provide a clean, easily controlled source of renewable energy from organic waste materials for a small labour input, replacing firewoood or fossil fuels (which are becoming more expensive as supply falls behind demand). During the conversion process pathogen levels are reduced and plant nutrients made more readily available, so better crops can be grown while existing resources are conserved.
Since small scale units can be relatively simple to build and operate biogas should be used directly if possible (for cooking, heating, lighting and absorption refrigeration), since both electricity generation and compression of gas (for storage or use in vehicles) use large amounts of energy for a small output of useful energy. This concept is suited to "distributed" systems where waste is treated near the source, and sludge is also reused locally, to minimise transport and initial capital cost compared to a "centralised" system. As the distributed system will need a support network biogas contributes to the "triple bottom line"; benefiting the environment, reducing costs and contributing to the social structure.
source http://paksc.org