© 2007 IWA Publishing. Organic Waste Recycling: Technology and Management. Authored by
Chongrak Polprasert. ISBN: 9781843391210. Published by IWA Publishing, London, UK.
4
Biofuels Production
With increasing population growth (Figure 1.1) and energy consumption (Figure
1.2), there have been a lot of interests worldwide to develop alternative sources
of energy to supplement the heavy demands on natural oil and gases. Biogas
(also called 'marsh gas'), a by-product of anaerobic decomposition of organic
matters (Equation 2.3), has been considered as an alternative source of energy.
The biogas can be used at small family units for cooking, heating and lighting,
and at larger institutions for heating or power generation. Another potential
source of renewable energy is ethanol, a liquid form of biofuel, which can be
produced from fermentation of organic wastes such as sugarcanes, molasses,
cassava and corn etc. Besides its current use as fuel, ethanol is also widely used
in the chemical, pharmaceutical and cosmetic industries.
The common raw materials used for biogas generation are often defined as
'waste materials', e.g. human excreta, animal manure, sewage sludge, and
vegetable crop residues, all of which are rich in nutrients suitable for the growth
of anaerobic bacteria. Although some of the above materials can be used
directly as fuels and fertilizers, they could be used for biogas production, as