Integrated Environmental Biotechnology - Environmental Biotechnology: Theory and Application - page 240

Figure10.4 Energyfrombiogasutilisation
The relative ease with which liquid fuels can be transported and handled,
coupled with their straightforward delivery to, and inherent controllability of
combustion in, engines makes them of considerable importance. Ethanol is a
prime example in this respect, since it can be used either as a direct replacement
for petrol, or as a co-constituent in a mix. Though at 24 GJ/m 3 , it has a lower
calorific value than petrol (39 GJ/m 3 ), in practice any performance discrepancy
is largely offset by its better combustion properties.
There are thriving ethanol industries in many countries of the world, generally
using specifically energy-farmed biomass in the form of primary crop plants, like
corn in the US and sugarcane in Brazil. In another example of the importance
of local conditions, the production costs of ethanol and the market price realised
by the final fuel depend on many factors external to the technology itself. Hence
the indigenous economy, employment and transport costs, government policy,
taxation instruments and fiscal incentives all contribute to the overall commercial
viability of the operation.
Brazil, where ethanol/petrol mixing has been routine since the 1970s is an
excellent example. Although the country's use of ethanol partial substitution has
a relatively long history, dating back to the 1930s, the real upsurge of accep-
tance of 'gasohol' lay in an unusual combination of events, partly driven by the
energy-crisis of the mid-1970s. Rising oil prices, which increased by over 25%
in less than two years, came at the same time as a fall in sugar revenue follow-
ing a slump in the world market. The Brazilian sugarcane industry, which had
shortly before invested heavily in an extensive national programme of moderni-
sation, faced collapse. Against this background, the production of fuel from the
newly available biomass crop became a sound commercial move, simultaneously
reducing the country's outlay on purchased energy and buoying up one of its
major industries.
The keynote of this chapter is the potential for integrating biotechnologies.
In the preceding discussion of biogas, this involved the marrying together of
the goals of biowaste treatment and energy production. In a similar vein, as was
described in an earlier chapter, there have been various attempts, over the years, to
produce ethanol from various forms of waste biomass, using naturally occurring