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Mrs Gayashree with her BIOTECH biogas plant and umbrella to protect it from falling coconuts.

Kerala is a relatively prosperous state in South India, with a growing middle-class population. Leaving out waste food is simply not acceptable in this suburban environment as it attracts crows and rats and smells bad. There is a demand for clean and hygienic disposal of waste for homes, institutions and municipalities. Many local councils do operate door-to-door waste collection services, but animals tear open rubbish sacks to get to food waste, and create more litter.

In 1994, driven by a desire to see an end to the dumping of waste in public places, Saji Das set up BIOTECH to focus on ways of managing organic waste to produce alternative sources of energy. Four years later BIOTECH launched its innovative biogas programme which uses unwanted food waste and other organic waste to produce gas for cooking and, in some cases, to produce electricity.

Mr Suresh Mohan, Ambalamukku is one of BIOTECH's happy customers: "My plant is one of the first that Biotech built. It is ten years old. It gives me one to two hours of gas a day. I sometimes ask for food waste from the local shops to get more gas. I get more coconuts from my trees when I use the effluent on the roots."

In order to have a real impact on the waste problem in Kerala and to produce significant amounts of clean energy, BIOTECH has developed biogas digesters that are not only suitable for domestic use but also for schools and hostels and larger municipal sites. To date BIOTECH has built and installed 12,000 domestic plants, 220 institutional plants and 17 municipal plants that uses waste from the municipal fish markets to produce biogas which is then used in a 3kW engine to generate electricity for lighting the market.

Around 160 of the domestic plants installed also use waste from 'eco-friendly' toilets. Using excreta in the digesters helps manage human waste at source and avoids ground water contamination. BIOTECH'S use of latrines is considered to be a major breakthrough in combating water and air-pollution. Mrs Anna Benedict from Kumbalangi island panchayat, comments: "Before we had the plant, all the waste went into the sea. Now we have a latrine and biogas plant, the waste is treated properly."

In Kadakal Panchayat (council) BIOTECH has installed the first integrated waste management system of its kind with a capacity of about one tonne of waste per day. The municipal solid waste is sorted by hand into wet waste, dry bio-degradable waste, glass, plastics and metal. The wet waste goes into a biogas plant and other materials are sold for recycling. Blood and wash water from a local abattoir is also taken by the plant, but uses a separate digester so that the bacteria becomes optimised for the specific waste type, and a suitable retention time can be established. The introduction of this system has paved the way for a new thinking in waste management projects across the state of Kerala.

The disposal of food waste and the production of clean energy are not the only benefits of BIOTECH's scheme. The plants also replace the equivalent of about 3.7 tonnes/day or 1,400 tonnes/year of LPG and diesel which in turn results in the saving of about 3,700 tonnes/year of CO₂, with further savings from the reduction in methane production as a result of the uncontrolled decomposition of waste, and from the transport of LPG.

"Before I had the plant, I had to walk 30 minutes to put my waste in the corporation bin. Before, one cylinder of LPG lasted 40 days, now it lasts 70. There have been no problems. Four or five friends have seen it and now want one." Mrs Dolly Ravikumar, NCC Nagar

Households with a biogas plant replace about 30% of LPG or about 44 kg per year, saving Rs1,200 per year. This means that the family can pay back their contribution to the cost of the plant in about three years, and even more quickly if they collect extra food waste from shops to increase their biogas production. The effluent or residue in the biogas plant also makes good fertiliser which results in higher food production.

BIOTECH's successful scheme is a great model for use in rapidly growing urban areas where the safe disposal of organic waste at source is important for hygiene and cleanliness, and the value of the gas produced is significant for households and institutions. However, there is perhaps even greater potential for replicability at the municipal level, where there are serious public health risks from large volumes of organic waste, including pollution of water supplies.

Ashden Award money will be used to publicise the benefits of the programme and to extend the use of the technology to other parts of India.