PhD Thesis - Energy Systems Research Unit - University of Strathclyde

carbon dioxide via steam reforming. The biogas resulting from the gasification
process already contains these three gases, in varying quantities, and any
methane present can also be converted via steam reforming, if desired. These
three gases then react, in the presence of a catalyst, to form methanol, and extra
carbon dioxide may be added to allow a more complete use of any hydrogen
created by this process [21]. Well-proven technology exists on a range of scales
for this continual process, and heat is required to distil the methanol produced
[82,83].
2.5.7 Landfill Gas Processing
Landfill gas occurs naturally in landfill sites as the organic matter decomposes,
by anaerobic digestion, to create a methane-rich biogas (about 55% methane and
45% carbon dioxide). In fact, new landfill sites can be specially developed in a
configuration that encourages anaerobic digestion, and optimises biogas
recovery. As methane is around 21 times more effective than carbon dioxide as
a greenhouse gas, it is better, where it is being produced, to convert it to a less
harmful substance, while also gaining useful energy from it. Useful quantities
of landfill gas can be available from a site for 10 to 30 years, and a typical site
can produce up to 1000 m 3 /hr. Around 10% of the electricity made from the
biogas will be used for its recovery (for pumping etc) [16,52]. This resource
will gradually disappear as less waste is put to landfill, but is still a useful
interim source of fuel.
2.5.8 Waste and Biomass Processing Technologies
Many waste and biomass fuel sources require to undergo some type of
processing before they can be easily used in boilers, heaters, turbines, engines
etc. The purpose of this processing may be to increase the fuel density to allow
easier transportation or storage (e.g. briquetting or pelletising), to dry out a wet
feedstock (e.g. sewage or wood drying), to reduce the feedstock size (e.g.
chipping), or to create a more homogenous fuel (e.g. shredding of waste
materials). These processes all require energy in the form of heat and/or
electricity [52,84,85].
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