The World in 2030

204 The World in 2030
But leaving aside the fortuitous re-use of cooking oils,
general transport biofuels include diesel replacements
(biodiesel) and sources of such energy range from sugar
cane (the most efficient) to wood (at present, the least
efficient). All sorts of issues affect how carbon-efficient,
or inefficient, biofuels may be. These include the energy
and water used to grow the fuel feedstock, the quality
of agricultural land required for growing, the carbon
emitted to assist the growing (in the production and use
of fertilisers, for example) and the energy efficiency of the
refined fuels themselves. For example, sugar cane provides
between eight and nine times the energy used in producing
them, while energy from rape seed oil and other similar
temperate crops produces only one to three times the
energy used in their cultivation. 388 Then there are the issues
of the energy used in converting specific crops into usable
energy and the energy consumed in transporting such fuels
to their final destination. Also of vital importance is the
issue of giving land over to the production of biofuel (in
some cases leading to the destruction of forested areas or
the usurpation of food-producing land).
Because these issues are so complex many consumers
are, at present, unable to make a meaningful choice about
biofuels; far more information is needed on this topic and
governments will soon have to regulate to ensure that only
the most efficient and environmentally benign forms of fuel
make it onto the gas station forecourts. Environmentalists
have a useful rule of thumb on this topic. They say that a
biofuel must emit at least 50 per cent less carbon (during its
cultivation, transportation and consumption) than the fossil
fuel it will be replacing to make it a useful substitute.