Pune is an affluent city in south India. However waste food is often discarded at the side of the road, attracting stray dogs, flies and rats and creating a public health hazard. ARTI has developed a biogas plant which uses food waste to supply biogas for cooking, replacing liquid petroleum gas (LPG) or kerosene. The plant is sufficiently compact to be used by urban households.
ARTI is a charitable trust, founded in 1996 by a group of scientists, technologists and social workers. It focuses on developing new rural technologies and on enabling other people to spread such technology to those who will benefit. The biogas project, begun in 2003, is one of over ten different projects run by ARTI. Many staff are involved in more than one project so there is continuous cross-fertilisation of ideas. Between 2006 and 2009, staff numbers grew from five to 29.
How does it work?
Biogas systems take wet organic material (feedstock) into an air-tight tank, where bacteria break down the material and release biogas – a mixture of methane with some carbon dioxide. A pipe takes the biogas to the kitchen, where it is used to cook with a biogas stove or for other purposes.
Most biogas plants in India and elsewhere are designed to use animal manure as their main feedstock, and are therefore only used in rural areas. ARTI developed a compact biogas plant which uses organic materials available in urban areas, such as waste flour or kitchen waste, as feedstock. This feedstock has a higher energy density compared to manure, and digestion takes place much more quickly (typically 1 to 2 days, compared with 30 to 40 days for a manure-based plant), so a smaller quantity of decomposing material needs to be held in the plant at any one time. One kg (dry matter) food waste feedstock produces about 0.25 kg of methane, whereas 20 kg of cattle dung feedstock would be needed to produce the same quantity of methane.
We use the effluent as a fertiliser for the plants. We also don’t have any odour problems (from the biogas plant).
How much does it cost and how do users pay?
US$1 = Rs 47 (Indian Rupees) [November 2009]
A compact biogas plant with a biogas stove costs about US$200 (Rs 10,000) to buy, but costs nothing to run if it uses only food waste. Even if waste flour is bought for feedstock, the running cost is only about US$0.04 (Rs 2) per day. There are no subsidies, so owners pay the full cost of the plant, although some suppliers accept payment in instalments.
How is it manufactured and maintained?
ARTI trains local entrepreneurs also representatives of other NGOs to produce and install biogas plants. By 2006, 30 people had been trained and ten had established themselves as entrepreneurs.
About 700 biogas plants were in use in 2006, in both urban and rural households in Maharashtra. A few have been installed in other parts of India and elsewhere in the world.
ARTI estimated that using only household food waste in a biogas plant halves the use of LPG or kerosene for cooking, saving a typical urban household 100 kg/year of LPG or 250 litres/year of kerosene. This is equivalent to 300 to 600 kg/year CO2. Further reductions in fossil fuel use and CO2 emissions arise from not having to transport LPG cylinders to be re-filled.
Indoor air pollution is reduced by cooking with biogas rather than wood or kerosene. This reduces respiratory and eye problems for those in the kitchen, most of whom are women.
Using food waste in a biogas plant means that less of it is now discarded by the roadside, reducing the public health hazard.
An ARTI biogas plant and stove costs about US$200 (Rs 10,000), compared with only about US$100 (Rs 5,000) for an LPG bottle and stove. However, LPG costs about US$0.60 (Rs 30) per day. If biogas halves the amount of LPG used, then the cost of a complete biogas system is saved within two years. Some families who use a pressure cooker for cooking and collect food waste from their neighbours have replaced all their LPG use.
Potential for growth and replication
ARTI estimates there are 500,000 potential users of compact biogas plants in Maharashtra State alone, and several other states in India have expressed an interest in the technology. ARTI has produced a CD showing how the plants are made, to encourage widespread adoption of the technology.
The plant can be used anywhere provided that there is enough space and the temperature is sufficiently high – anything above 30ºC. ARTI has looked at ways to insulate biogas plants to increase gas production in the coolest months.
Update: what happened next?
Since their 2006 Ashden Award, ARTI have developed other pilot installations such as the ‘balcony’ biogas plant for apartments, where space is limited; and a wood burning gasifier stove.
In partnership with GERES, the French NGO, ARTI has carried out a preliminary assessment of greenhouse gas savings from biogas plants in urban areas. The analysis assumes CO2 savings as a result of cleaner rubbish disposal and partial substitution of LPG as cooking fuel, and estimates that the average biogas plant saves approximately 0.3 tonnes/year CO2. However, the floating dome structure of the plant can result in leakage of methane, thus reducing CO2 savings. ARTI is currently working on design improvements to minimise the methane leakage without compromising user friendliness.