The will, the waste and the water

In Germany it has been called a revolution: 1500 plants installed in the last ten years, and many hundreds more in the pipeline. In China, millions of families observe the daily routine of stirring, feeling for consistency, adding new material and water when necessary. The technology, so enthusiastically adopted, is indigenous to neither country, originating more than a century ago in India. So why, despite numerous pilot projects over at least the last 70 years, has production of biogas energy failed to find friends in Africa?

Water, or the lack of it, is a major factor. Unlike composting, production of biogas is an anaerobic process; the bacteria who constitute the 'main players' in the system need to be kept warm, dark, wet and oxygen-starved to maintain their prolific methane-making. Regular stirring of their slurry soup allows the stirrer to monitor and maintain their watery world, as well as keeping them circulating and feeding efficiently. But without regular additions of water, gas production falters. Failure in compost-making schemes are often attributed to lack of water, but with biogas the chances of success in water-scarce environments are even slimmer. Having sufficient waste matter is also crucial, a factor that tends to deny the technology to households with few livestock, and makes life difficult for those whose animals graze freely. Collecting dung deposited by grazing animals is an unpopular burden. A pilot scheme in Ghana's greater Accra region failed, in part because it was never established who would be responsible for collecting the waste material.

The right incentive
Human commitment may be fundamental to success, but such commitment depends on incentives. The experience in Germany has resulted from more than just the availability of water and dung. In 1999 a law was passed raising the price paid for electricity generated from biogas-powered turbines by 40%; suddenly biogas plants were worth the investment. In the African context, that incentive may have to be different. In Addis Ababa for example, an agricultural development project called the Biofarm has found a way of giving biogas production several vital functions within a much bigger enterprise. Not only is methane from the biogas digester used to power lights and stoves, but the digested slurry is piped, by force of gravity (the cattle barn and digester are located at the highest point of the farm), to garden plots for use as liquid fertilizer. There it supplies the nutrients for several hectares of premium organic vegetable production, sold to the urban market. The Biofarm has also devised a system for compressing and bottling the gas, and this technology has now been adopted by several 'bio-villages' linked to the original farm. Some of them are even using the bottled gas to power water pumps.

Surplus gas and slurry offer further incentives to production. While the former can now be bottled and supplied to consumers who are not directly connected to a biogas scheme, the latter can also be processed and packed for sale as dried fertilizer if the community are unable to make efficient use of it in their own plots. Agro-processing can also benefit from biogas power, particularly in remote areas where oil or electrical power are unavailable. For example, a pilot project in Nigeria has used biogas for drying and cooking cassava chips. However, in addition to such incentives there is also need for well-planned training. Keeping a biogas digester healthy and productive is often compared to looking after an animal. In China, it is said, the people have a 'feel' for how their digesters are functioning. The bacteria need daily attention to their food and water requirements, with no weekends or holidays for their keepers. Maintaining gas production demands a thorough understanding of the technical dynamics of the system, and, arguably, some belief in the broader advantages of renewable energy.

A costly exercise?
Beyond the need for incentives and training, there is of course a financial restriction. For most rural families, the cost of establishing a biogas system will be prohibitive unless they are able to pay in instalments. In Ethiopia, a small system suitable for one household costs US$500, roughly equivalent to the market value of between two and three years' firewood, for an average family. For cooking purposes, solar cookers are more cost effective in the right environment. The Biofarm has trialled an extremely efficient solar cooker which costs less than $100. This saving does, however, have to be considered in the light of solar systems' greater vulnerability to theft. Obtaining suitable lamps and stoves also has cost implications for biogas users, and any such equipment must be specifically designed to cope with the characteristics of the gas, including its powers of corrosion.

In Europe, belief in the earning potential of biogas has led some farmers to turn their fields over to biomass crops, literally cultivating energy. For some parts of rural Africa, particularly those suffering deforestation and poor infrastructure, the technology could supply the energy so badly needed to support agricultural development. But establishing production requires investment and incentives, and for these to come, the long-term viability of biogas systems in Africa still has to be proved.

For another example of a successful use of biogas see 03-2 Picture feature.