Biogas is a clean source of cooking fuel

The plants are tackling the ongoing problem of burning wood and kerosene in domestic stoves. Polluting to the immediate and wider environment, these stoves also do little for the working lives of users, many of whom are farmers for whom better crop yields are of prime importance.

This need to provide a robust economic incentive for adoption led VK-NARDEP to develop a plant that not produces valuable biogas for cooking but also processes the left-over slurry to make a high quality fertiliser as its by-product.

It’s safer than LPG, there’s less heat from the flame; so I feel I can relax. It’s quicker, too. We feed 350 here, all by biogas.

Mrs Ras Kumari, head cook, Donavur Fellowship

Background

The southern part of Tamil Nadu is hot and humid. Most people work in agriculture and grow rice, sugar cane, mangoes, coconuts and a range of vegetables. The biogas plants sold by VK- NARDEP use cattle manure to provide clean biogas for household cooking, replacing the use of fuelwood or Liquefied Petroleum Gas (LPG). Fertiliser is also produced from the biogas residue, and VK-NARDEP has developed a range of techniques to enhance the quality of this fertiliser.

The organisation

VK-NARDEP is part of Vivekenanda Kendra, a spiritual centre and research institute based at Kanyakumari in Southern India. The organisation focuses on energy efficient technologies for rural areas, watershed management, holistic health, sustainable agriculture and renewable energy. It also coordinates networks of self-help groups among the villagers in the region. In 2009, it employed 15 people. VK-NARDEP is financed by grants and charitable donations.

The solid residue from biogas plants replaces chemical fertilisers

The technology

How does it work?

Biogas systems take organic material such as cattle dung into an air-tight tank where bacteria break down the material and release biogas – a mixture of mainly methane and carbon dioxide. The biogas can be burned as a fuel, for cooking or other purposes, and the solid residue can be used as organic compost.

VK-NARDEP has developed techniques to increase the value of the residue, including using worms (vermi-composting) to enhance its fertiliser quality, or growing Azolla which can be used as animal feed or fertiliser.

How much does it cost and how do users pay?

US$1 = 47 Rupees (Rs) (July 2006)

The deenbandhu plants that VK-NARDEP supply cost from US$213 to US$745 (Rs 10,000 to Rs 35,000) depending on size. At the time of writing (2006), purchasers pay 80% of the cost and the remaining 20% is paid as a subsidy by the Government on condition that they engage an approved installer. VK-NARDEP helps the customer arrange credit from a rural development bank or co-operative society. It also ensures that the loans are used for the intended purpose and that the customer re-pays promptly. Generally loans can be paid back within two year through savings made on fuelwood, LPG and chemical fertiliser.

Biogas plant at the Swami Shivananda Hospital, southern India

How is it maintained?

VK-NARDEP is careful to ensure that users really want a biogas plant and understand how it works. To do this, the user must buy the materials (to a VK-NARDEP specification), provide food and lodging to the installer and have at least one member of the family help with plant construction.

The government pays VK-NARDEP a fixed annual service fee of US$15 (Rs 700) for three years after the installation of a plant. During this period, VK-NARDEP services the plant free of charge and provides any additional training to the customer. After three years VKNARDEP gives the owner a checklist for maintenance and continues to provide advice free on request, but payment is required for any work on the plant.

VK-NARDEP has also carried out a detailed analysis of more than 2,000 existing biogas plants across India, and used the findings to produce seven guides to biogas and farming in a range of languages which are distributed via the government and NGOs.

Benefits

Between 1986 and 2006 VK- NARDEP sold and installed 2,000 biogas plants in southern Tamil Nadu, directly benefiting around 12,000 people and indirectly benefiting many more through agricultural opportunities and plant maintenance work.

Cooking on biogas

Environmental benefits

The biogas produced for cooking usually replaces fuelwood or LPG, with wood previously purchased or collected by poorer people from forest areas. The 2,000 biogas plants installed by 2006 were saving about 5,000 tonnes/year of wood.

Where wood is from non-sustainable sources, this saving also reduces greenhouse gas emissions. The potential saving is around 4 tonnes/year CO2 per plant, or 8,000 tonnes/year CO2 in total. Households with biogas plants no longer store heaps of cattle dung, and the release of methane (a greenhouse gas) from stored dung is avoided.

The solid residue from biogas plants replaces chemical fertilisers, reducing the run-off of nitrates into ground water and the release of nitrous oxide (a greenhouse gas). The residue also suppresses weeds and reduces the need for chemical herbicides which contaminate water supplies.

The biogas residue and the composts made from it save on the cost of fertiliser and increase crop yields by 20-30%

Social and health benefits

Using biogas saves time previously spent collecting fuelwood and cooking. The kitchen stays cleaner, there is less smoke and soot, and the stove is more controllable. Women suffer less from respiratory diseases. The elimination of dung-heaps has reduced the number of flies around homes, and the incidence of fly-borne diseases.

Economic and employment benefits

The biogas residue and the composts made from it save on the cost of fertiliser and increase crop yields by 20-30%. VK-NARDEP estimates that the owners of a 4 m3 plant can save US$110 (Rs 5,100)/year on fertiliser, as well as US$180 (Rs 9,500)/year on fuelwood.

Azolla, grown using the biogas residues, reduces the need to buy livestock feed for animals and poultry, and has led to the production of better quality milk and eggs fetching higher prices.

Potential for growth and replication

The compost value of biogas residues could be improved for any type of dung-based biogas plant using the techniques developed by VK Nardep. There is thus significant potential for replication of these compost-enhancing techniques in other parts of India and elsewhere.

Update: what happened next?

By 2009, a total of 2,500 biogas plants had been installed by VK-NARDEP, including 100 of the VINCAP design. In total, about 15,600 people benefit from these plants.

Much of VK-NARDEP’s work since winning the Ashden Award has focussed on research and development. It received a US$100,000 grant from the Ford Foundation to look at purifying methane from the biogas and compressing this into a cylinder, to replace compressed natural gas in cars. It also received a grant from NABARD in Mumbai to install a number of small domestic biogas plants in different agro-climatic zones in India, in order to evaluate their performance and standardise a design. Finally, a grant from the National Research Development Corporation in New Delhi was used to produce a research paper on the production of methane from water clogging weeds.

VK-NARDEP is part of Vivekenanda Kendra, a spiritual centre and research institute based at Kanyakumari in Southern India. The organisation focuses on energy efficient technologies for rural areas, watershed management, holistic health, sustainable agriculture and renewable energy. It also coordinates networks of self-help groups among the villagers in the region. In 2009, it employed 15 people. VK-NARDEP is financed by grants and charitable donations.