Geography Reference
In-Depth Information
Table 53
(contin
ued)
Source
Specific problems to be overcome
Biofuels
Based on deriving these products from crops rich in sugar or starch or oil.
Mixed with regular gas or petrol, a result of national regulations not initially
commercial viability, it contributes about 10 % of the fuel used in U.S.
vehicles in 2012. The big problem is that many use food crops for the feed-
stock, for example creating ethanol from corn, resulting in a large proportion
of the American crop devoted to ethanol production because of the subsidies
available for the processing. But this has helped increase the cost of com and
produced a 'food versus fuel' argument. If more and more corn or other food
crops are used, the cost of food will increase, which will cause problems for
the poor in a growing world, while the approach does produce a low energy
output, given all input costs in growing and processing. Small amounts of
second general bio fuels are being manufactured, using various techniques;
these break down plant waste or woody crops into sugars to produce a
cellulosic ethanol. The product is still more expensive than the previous
approach but initially seems more sustainable since waste, such as sugar
cane and grain stalks, leaves and wood chips are used. Yet some of these are
a traditional ingredient for fertiliser, while there is increasing concern that
plantations of imported plants to provide the biomass will upset local ecologi-
cal balances, which may lead to a 'vegetation versus fuel' debate. Moreover
the biomass feedstock required for large scale plants is also very big, which
means high collection costs and often the consumption of vast acres of land
that may soon be needed for food, if production is to be drastically increased.
So although a useful addition to total liquid fuel supplies, there are clearly
some negatives when the indirect and effects are added to the direct effects.
Research in the use of algae to create a biofuel is promising, but is still a long
term solution.
Bio-gas
Derived from two sources with the advantage of being available near cities
creating low-transmission costs. One is by anaerobic decomposition of rub-
bish that creates methane that can be used to generate electricity, as in the 60
year old Los Angeles 500 ft high landfill that supplies 70 thousand homes.
Another is by combusting household waste, or waste from forestry plants to
produce gas to drive turbines. This involves the expense of obtaining waste
and the development of conversion plants. Pollution from waste-generating
plants in the past led to a reduction in this approach. But new Waste-To-
Energy technologies show much promise and offer an alternative to landfills
or recycling rubbish. They are based on high energy burning at over 850 ﾰC,
which breaks down the molecular bonds in toxins such as dioxin and furans,
making them harmless, while the flue gases can be used to produce stream to
drive turbines that creates electricity. This approach is likely to increase in use.
Wind
At first sight a free and available source to drive turbines on windmills that
produce electricity. But not all areas have regular winds. Generation is often
intermittent and greater at night, but high electricity demands are in the day.
Generating capacity, given varied wind supply, averages only 25 % of capac-
ity of the turbines under current technology, though offshore sites are often
50 % more efficient because of stronger winds. Local noise and aesthetic
intrusion, as well as hazards for bird life, has led lo increasing opposition to
land wind farms. Extra costs come from adding transmission lines from rural
production sites to distant urban places. Technological advances in turbine
design mean costs are increasingly competitive with fossil fuels. But storage
of excess wind power is still a problem, although it can be used to pump
water to hydro reservoirs in hilly country or to geo-thermal stores.
