69
Reading Passage
9
Biofuels backlash
A
Biodiesel and bioethanol are cleaner, sustainable alternatives to petroleumbased
fuels, which continue to deplete. Biofuels can be grown repeatedly from crops making
them 100% renewable. Bioethanol is made in a similar way to ‘moonshine’ by fer
menting cereals like corn and maize and then distilling the brew to evaporate the
ethanol. Biodiesel is manufactured from the vegetable oils found in sunflower seeds,
rapeseed and the oil palm. Gasoline (petrol) engines can be tuned to run on 90%
ethanol blended with 10% petroleum and biodiesel is a direct replacement for exist
ing road diesel.
B
Carbondioxide is the principal manmade greenhouse gas. It traps heat in the
atmosphere and increases global warming, causing polar ice to recede and sea
levels to rise. Energy crops offer one solution to the deleterious effects of carbon
dioxide emitted from vehicle exhausts. Biofuels are 100% carbonneutral, which
means that there is no net gain or loss of carbon to the environment when the fuels
are burnt. The carbondioxide does not add to the total amount in the atmosphere
because the crops absorb the equivalent amount of carbondioxide by photosynthesis
as they grow. Consequently, the ‘carbon footprint’ of gasoline and dieselpowered
vehicles can be reduced by switching to bioethanol or biodiesel. The latter burns
more efficiently than petroleum diesel leaving less unburned hydrocarbons, carbon
monoxide and particulates, which means less atmospheric pollution as well as less
global warming. Biofuels are less toxic than fossil fuels and biodegrade if spilt on the
ground.
C
Not everybody believes that biofuels are the ideal alternative to fossil fuels. The
status of biofuels as environmentally friendly can be challenged on several counts.
Firstly, to provide space for energycrop plantations, trees are felled and burnt which
creates a surplus of carbondioxide. Secondly, in tropical rainforests the loss of trees
threatens biodiversity by destroying habitat. Thirdly, deforestation increases the
evaporation of water from the ground, which can lead to extensive droughts. These
deficits can be discounted if the energy crops are planted on existing agricultural
land, but if this is done it reduces the supply of food crops, creating a surge in food
prices. Furthermore, in developing countries people have barely sufficient food to eat
and switching to fuel crops could threaten their meagre food supplies.
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