Integrated Environmental Biotechnology 237situation is less than ideal. For one thing, burning denies the bridge discussed
above, by allowing little or no opportunity for reclamation. If we extend this
to larger environmental issues, like reducing CO 2 production and the usage of
fossil fuels, biomass, and hence environmental biotechnology, comes to occupy
a pivotal position in the sustainability debate.
Bioenergy
The concept of obtaining energy from biomass material was mentioned earlier, in
respect of the biological waste treatment methods involving anaerobic digestion
and fermentation, and represents nothing particularly novel in itself. Methane
and ethanol have been long established as fuels in many parts of the world,
their production and utilisation being well documented. Both of these may be
described as derived fuels, biochemically obtained from the original biomass.
However, to many people around the globe, the most familiar forms of biofuel
are far more directly utilised, commonly via direct combustion and, increasingly,
pyrolysis. Around half the world’s population relies on wood or some other
form of biomass to meet daily domestic needs, chiefly cooking. Estimates put
the average daily consumption of such fuels at between 0.5–1.0 kg per person
(Twidell and Weir 1994a). This equates to around 150 W which is an apparently
high figure, but one largely explained by the typical 5% thermal efficiency of the
open-fire method most commonly encountered.
The energy demands of the developed world are well known to be enormous. In
the USA alone, the requirement for electricity has grown by 2.7% on average per
year over the past 10 years (Perkowitz 2000). TheExecutive Order on Biobased
Products and Bioenergy, August 1999, set out the goal of tripling US biomass
use by 2010, which has been estimated to be worth around $15 billion of new
income, while at the same time reducing carbon emissions by the equivalent of
removing some 70 million cars from the road (Feinbaum 1999). The European
Commission has also suggested that the EU as a whole should aim to double
the current contribution made by renewable energy sources, taking it to 12%,
also by 2010. Under this proposal, biomass energy was to provide an additional
90 million tonnes of oil equivalent (Mtoe) per year, raising its overall share to
137 Mtoe. Half of this would come from specifically farmed energy crops, while
other biofuel forms would account for the rest.
The energy of all biofuels derives ultimately from the sun, when incident
solar radiation is captured during photosynthesis, as discussed in Chapter 2. This
process collects around 2× 1021 joules of energy, or 7× 1013 watts, each year,
throughout the biosphere as a whole. During biomass combustion, as well as
in various metabolic processes described elsewhere, organic carbon reacts with
oxygen, releasing the energy once more, principally as heat. The residual matter
itself feeds back into natural cycles for reuse. It has been calculated that a yearly
total of some 2. 5 × 1011 tonnes of dry matter circulates around the biosphere, in