How Energy Is Produced - The Renaissance of Renewable Energy - page 136

residues into biogas for cooking and lighting, and digestate to fertilize crops (Al Seadi and
Lukehurst 2012 ; IEA 2007 ; OECD/IEA 2008 , 2009 ) .
Converting Biogas to Biomethane
The energetic value of biogas is low compared with natural gas, as almost half of it
comprises carbon dioxide, which doesn't burn. The carbon dioxide can, however, be
filtered out, leaving biomethane, which can be used as a fuel in gas-powered vehicles or
sold to a larger natural gas network. In some cases biomethane is already economically
competitive with fossil fuels. In Austria and Germany, for example, many farmers grow
crops for anaerobic digestion to produce fuel for their own tractors, and in Sweden more
than 50 per cent of the fuel used for transport comprises biomethane (Fabbri and Soldano
2010 ; Petersson and Wellinger 2009 ).
Figure 4.46. A small biogas plant installed in Kerala, India, by BIOTECH, an NGO that
has helped install biogas digesters in more than 20,000 households. Source:
www.biotech-india.org .
Figure 4.47. Development status of the main bioenergy technologies. Source: IEA
Bioenergy ( 2009 ) (modified).