Environmental Engineering Reference
In-Depth Information
Noah's contemporaries had not only mastered the art of selective cultivation, they had
also learned to apply the natural reaction known as fermentation, one of the earliest forms
of biotechnology. This involves microscopic unicellular fungi (yeasts) that feed on the
sugars in fruit and vegetables releasing carbon dioxide and alcohol as waste by-products.
Both of these by-products have been harnessed by humans; the former to make dough rise,
the latter to make merry. After World War II, the use of fermentation spread from food
production to the pharmaceutical and energy industries. Thus was born the first generation
of biofuels; bioethanol from sugarcane or corn, biodiesel from vegetable oils and animal
fats, and biomethane from the anaerobic digestion of wet biomass.
While grains and sugarcane store energy in the form of starch or sugars, other plants,
such as olive, rapeseed, or palm, store their energy in the form of fats, in seeds or fruits.
The process of exploiting plant oils is more mechanical than biochemical; the seeds are
simply crushed or squeezed to release the oils. The vegetable oils we use in the kitchen are
alreadysuitableasfuels.Theyhaveacalorificvaluesimilartodiesel,justdifferentphysical
properties. The main obstacle to the direct use of vegetable oils in cars is their density
fats can be converted into the more fluid and easily flammable biodiesel. Its energetic and
physical properties are so similar to fossil diesel that a 5 per cent blend can be used in a
Grassoline
: The Promise of Second-Generation Biofuels
Most of the feedstocks used to produce first-generation biofuels are food crops. As more
countries embrace biofuels, both as an alternative to oil and in response to climate change,
their impact on the price of agricultural commodities grows. Already in 2007, a quarter of
the American maize crop was destined for biofuel production (Kingsbury
2007
). In 2008
there was a sharp rise in the global price of key food commodities, such as maize, wheat
and soybean. Many, including the World Bank and several leaders of developing countries,
were quick to blame biofuels, and the 'food versus fuel' debate made international
headlines. This was often characterized as a choice between the gas tanks of the world's
richest people and the bellies of its poorest. Jean Ziegler, the UN Special Rapporteur on
the Right to Food, went as far as to call for a five-year moratorium on the production
of biofuels. Subsequent analysis revealed that the main cause of high food prices was
food and energy demands continue to increase, this debate is unlikely to abate. Both the
Food and Agriculture Organisation and Greenpeace caution against too strong an embrace
