296 Energy andtransport for thefutureFigure 11.10The processes involved in the sugar cane industry.
other biomass fuel sources provided nearly eighty per cent of what is
required for the city’s heating.
But what about the greenhouse gas generation from waste inciner-
ation? Carbon dioxide is of course produced from it, which contributes
to the greenhouse effect. However, the alternative method of disposal is
landfill (most of the waste in the UK currently is disposed of that way).
Decay of the waste over time produces carbon dioxide and methane in
roughly equal quantities. Some of the methane can be collected and
used as a fuel for power generation. However, only a fraction of it can
be captured; the rest leaks away. Because methane is a much more ef-
fective greenhouse gas, molecule for molecule, than carbon dioxide,
the leaked methane makes a substantial contribution to the greenhouse
effect. Detailed calculations show that if all UK domestic waste were
incinerated for power generation rather than landfilled, the net saving
per year in greenhouse gas emissions would be equivalent to about ten
million tonnes of carbon as carbon dioxide.^39 Since this is about five
per cent of the total UK greenhouse gas emissions, we can infer that
power generation from waste could be a significant contribution to the
reduction in overall emissions.
Other wastes resulting from human or agricultural activity are wet
wastes such as sewage sludge and farm slurries and manures. Bacterial