Environmental Engineering Reference
In-Depth Information
and thus can be used to compensate for the variations in the nondispatchable renewables and
the system load. Whether there will be suffi cient biofuels for this purpose will depend on the
available land area for energy crop production in relation to the amount of balancing plant
required.
Biomass resources in most countries are large; for example in the UK is has been estimated
that up to 20 million tonnes could be available per annum. It is important to distinguish
between fi rst generation crops that have been developed for food (sugar beet, oil seed rape
and wheat grain) that may be used for chemical conversion to biodiesel and bioethanol and
second generation lignocellulosic (biomass) crops that can be used as feedstock for heat,
power and liquid fuels.
First-generation technologies have in general a poor carbon footprint and represent an
'intermediate step' towards second-generation lignocellulosic feedstock. Research is needed
on the environmental impact of the wide-scale growing of biomass crops. At present there is
limited understanding on how the different bioenergy chains compare in environmental
impact.
There are also concerns that dedicating signifi cant land area to bioenergy crops will put
pressure on food production and result in unwanted increases in food costs. Impacts on
food prices in the USA and China have been reported recently, but these refl ect the use of
corn for the production of liquid fuels for transport, rather that fuels for electricity
generation.
8.5 The Future of Hydro and Marine Power
Although small scale hydro installations can make a useful local contribution to electricity
generation there are a limited number of suitable sites and thus the overall impact on
electricity system operation is limited. This is unlikely to change with time. Larger scale
hydro is a different matter. In countries like Switzerland and Norway with a large proportion
of hydro power, the power systems are already designed around these resources and
their characteristics. Some parts of the world have yet to develop their hydro potential
fully and as they do so attention will be paid to the creation of a suitable system
infrastructure.
Tidal power, as summarized in Chapter 2, has a large contribution to make in geographical
areas that experience a large tidal range. To date this resource has barely been touched. Since
the technology for barrage construction and turbine construction is already available, it can
be concluded that it is unfavourable economics that presently inhibits the use of this tech-
nology. It is known that large tidal projects could take decades to pay back their installation
costs. Even though the civil works would last well beyond such timescales, nearer term
market pressures make these projects impossible to fi nance. Nevertheless, there will come a
time when fossil fuel shortages and rising energy costs will make the construction of large
barrage schemes attractive despite the adverse local environmental impact on wading birds
and other wildlife. Indeed the recent concerns for security of supply that are giving hope to
the nuclear industry should be prompting a re-examination of this technology, which poses
investment challenges that are not dissimilar. Both nuclear and hydro involve massive upfront
costs and these need to be paid back with profi t over their considerable lifetimes. As with
nuclear, states will need to decide how to facilitate the construction of large tidal barrage
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