Ethanol is used to make alcohol, distillation of the mixture leads to the isolation of pure ethanol, a good alternative to petrol. there is a debate among ecologists and scientists whether to use corn or cellulose to manufacture ethanol.

There are a group of scientists that believe cellulose is a better feedstock for ethanol than corn. it has been argued that the expansion of corn ethanol is damaging wildlife and the environment. As more cornfields are grown, protected land is being lost, and the birds are unable to use the corn as a habitat.

Corn requires large amounts of fertiliser, this takes a lot of energy to produce. Corn ethanol therefore only produces approximately 25% more energy than is required to produce the crop. The fertilisers used pollute streams killing marine life. running a car on corn ethanol only produces 13% less greenhouse gases than gasoline.

Studies show that cellulosic ethanol from native grasses could be a solution. Monitored plots of switchgrass (a large part of their mass is cellulose) has been shown to produce cellulosic ethanol that yields upto 15 times more energy than used in production. much less greenhouse gas is released as the plants remove more carbon dioxide than is released in production, unlike corn. By using plants a diversity can be used making it a better haven for wildlife.

The process of extracting sugar from cellulose is more complex than for corn starch. This is because cellulose consists of long flat chains of glucose which are packed very tightly together. The OH groups in the chain form hydrogen bonds making the cellulose hard to break down because of the numerous tightly packed hydrogen bonds.

Corn is a starch which is easier to break down. The polysaccharides in starch are branched chains that are connected in a way that they cannot be packed tightly together.

However cellulosic ethanol has big potential energetic and environmental advantages.

References

Jim Giles, (2007), can biofuels rescue American prairies? , New Scientist, 195, pp8 - 9

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