BIOTECH is an NGO based in Kerala, South India, which has developed biogas digesters for managing food waste and other organic waste in more than 20,000 households, 220 institutions and 19 municipal sites. The digesters are prefabricated from ferro-cement and gas collectors made from Fibreglass Reinforced Plastic (FRP) so that they can be installed quickly and easily on site and has no electric or moving parts.
Biogas is produced from the decomposition of the organic matter in anaerobic conditions, and in households and institutions the gas is used directly for cooking, giving savings of about 50% when displacing LPG use.
The main feedstock for the plants is food waste, but cow dung needs to be used initially to provide a culture of suitable bacteria to get the digestion process started. Food waste is simply mixed with organic wastewater from the kitchen in a bucket and poured into the plant inlet, and no additional water is needed. Biogas gradually collects in the gas holder as the waste decomposes, and a pipe is used to take it to a special biogas stove in the kitchen. A valve is used to open and shut the flow, and a regulator varies the flame. The effluent from the plants is virtually odourless and has a high content of nitrogen, phosphorous and potassium, so it can be used as a garden fertiliser.
Nearly 20,000 domestic plants have been installed, serving about 80,000 people.
Some systems take waste from toilets as well as kitchens, to reduce health risks and contamination of ground water, and with these systems up to 75% of LPG can be replaced. Larger systems are used at markets and municipal sites, and at these the biogas is cleaned and then used to run small engines to generate electricity for lighting.
The largest system is an integrated energy-from-waste plant that processes nearly three tonnes of organic waste per day, including sorted municipal waste and effluent from an abattoir. Here a number of individual digesters are used to manage the different types of organic waste, so that the bacteria in each digester become optimised for the specific waste type.
The cost of the plant is about 400$ and about half the cost is subsidized by grants from both the Ministry of New and Renewable Energy and the local body government. The pay back period for the system is less than 3 years.
It is encouraging to see such success stories and Panchabuta will aim to bring out such success stories in India. Readers are encouraged to contribute towards the same by sending an email to panchabuta.cleantech (at) gmail(dot)com.[youtube=http://www.youtube.com/watch?v=7O_l0d8vGms]