Overview of biogas extension

Abstract

An overview of biogas extension work considers the background to the development and use of the technology in less developed countries. The technology is placed in the wider global context of a concern for the environment since the early 1970s. It offers a long list of benefits to the users of the technology. A brief history looks at its origin in India and China, as well as applications for sewage processing in Europe and the USA. The benefits of biogas technology for small farmers led to programmes in China and India, which inspired the programme in Nepal. This book is the latest publication following a series of reports and a previous book about the biogas programme in Nepal. People in Europe and the USA have only lately realised that a technology for processing sewage is also a good source of renewable energy.

Keywords: biogas, anaerobic digestion, overview

The global context of the development of biogas extension programmes

Biogas has been seen as the classic example of a renewable energy technology or 'Appropriate Technology' since concerns were expressed at the rate of development in the world in the early 1970s. Several books at the time suggested that the world needed sources of energy other than oil. The key books were Limits to Growth (by Donella H. Meadows, Dennis L. Meadows, Jorgen Randers, and William W. Behrens III) (Meadows et al., 1972) from the Club of Rome in 1972; 'Small is Beautiful: A Study of Economics as if People Mattered ' by E.F. Schumacher in 1973 (Schumacher, 1973); and 'Our Common Future', the report of the Brundtland Commission (set up in 1983, but published in 1987) (Brundtland, 1987). The two oil price-hikes of 1973–74 and 1979–80, caused first by OPEC restricting their supplies and then by the first Gulf war, confirmed this concern, especially for leaders in developing countries that were badly affected by the price hikes.

In India and China, various groups had been experimenting since the 1930s with using animal dung to generate biogas. The idea had been fairly well known before that time. There are reports of a sewage gas plant built in Bombay in 1859 and the idea was brought to the UK in 1895, when the gas produced was used to light street lamps. The 1970s oil price-hike encouraged both the Chinese and Indian governments to invest in programmes to spread the technology into rural areas. The second hike encouraged greater emphasis on biogas in India and China; it also encouraged governments to start programmes in many other countries across the world, particularly in the USA, the UK and in mainland Europe.

The rapid drop in oil prices in the mid-1980s meant that many biogas programmes faltered. Those in the USA, Europe and many other places were abandoned. In China and India, biogas technology was seen as a way of offering development to rural farmers, encouraging them to stay on the land rather than moving to the cities. These programmes therefore grew slowly but steadily from their initial foundations, which allowed a large amount of expertise and experience to be built up. The Chinese government, in particular, has been keen to share its expertise with other countries, including African nations. Various groups in Germany, especially Bremen Overseas Research and Development Association (BORDA) and German Appropriate Technology Exchange or Deutsches Zentrum fur Entwicklungstechnologien (GATE) worked to spread information about these technologies in other parts of the world (Kossmann et al., 1999; Sasse et al., 1991).

The growing concern about the effects of climate change, combined with concerns about 'peak oil', since the early 1990s has triggered a new interest in biogas technology. The launch of the United Nations Framework Convention on Climate Change in 1994 (UN, 1992) and the subsequent Kyoto Protocol (UN, 2008) put pressure on many countries to develop alternatives to fossil fuels. Biogas is seen as an effective way to generate energy from agricultural and food residues that are often consigned as wastes for disposal.

The developed country that has taken most interest in biogas is Germany, based on its experience working in developing countries and also encouraged by the influential Green movement. Other European countries following close behind are Sweden, Denmark, Belgium and Austria. The USA has also developed a small, but steady, programme in biogas technology.

The countries that have built millions of biogas units, such as India and China, have a wealth of expertise that needs to be shared with the rest of the world.

Benefits of biogas technology

Biogas comes from anaerobic digestion, a process that uses naturally occurring microbes to break down food materials into methane and carbon dioxide in the absence of oxygen. The methane is very similar to natural gas, so is an easy-to-use high-grade fuel that can be used for cooking, heating or to run engines to generate shaft power or electricity. The presence of the carbon dioxide does reduce the heating value of the gas, but this does not seriously affect the value of biogas for these applications. However, the presence of carbon dioxide does make it more difficult to store biogas under pressure.

The microbes that break down food materials are similar to those used to compost the same materials. Aerobic composting generates water and carbon dioxide as well as heat. Using an anaerobic (without oxygen) process means the break down proceeds via a different pathway, so that energy is retained in the gas, rather than released as heat. The residue left after the digestion process is good compost, which can be used to enhance soil fertility and structure. The residue also has the huge benefit of having greatly reduced odour. Volatile fatty acids and other breakdown products are the source of the smells from rotting food and dung. Anaerobic microorganisms consume volatile fatty acids, which are the products of the breakdown of food materials by other microorganisms. Since methanogenic microorganisms use these volatile fatty acids to make biogas, they reduce the smell that the other microbes generate.

The microbes (which include both bacteria and archaea) that perform anaerobic digestion exist in the gut of cattle, as they help them digest grass and other plant foods. Most of the...