長文ですいません、和訳お願いします。
In principle, burning biofuels merely releases the carbon the crops accumulated when growing. Even when you take into account the energy costs of harvesting, refining and transporting the fuel, they produce less net carbon than petroleum products. The law the British government passed a fortnight ago - by 2010, 5% of our road transport fuel must come from crops - will, it claims, save between 700,000 and 800,000 tonnes of carbon a year. It derives this figure by framing the question carefully. If you count only the immediate carbon costs of planting and processing biofuels, they appear to reduce greenhouse gases. When you look at the total impacts, you find they cause more warming than petroleum.
A recent study by the Nobel laureate Paul Crutzen shows that the official estimates have ignored the contribution of nitrogen fertilisers. They generate a greenhouse gas - nitrous oxide - that is 296 times as powerful as CO2. These emissions alone ensure that ethanol from maize causes between 0.9 and 1.5 times as much warming as petrol, while rapeseed oil (the source of more than 80% of the world's biodiesel) generates 1-1.7 times the impact of diesel. This is before you account for the changes in land use.
A paper published in the journal Science three months ago suggests that protecting uncultivated land saves, over 30 years, between two and nine times the carbon emissions you might avoid by ploughing it and planting biofuels. Last year the research group LMC International estimated that if the British and European target of a 5% contribution from biofuels were to be adopted by the rest of the world, the global acreage of cultivated land would expand by 15%. That means the end of most tropical forests. It might also cause runaway climate change.
The British government says it will strive to ensure that "only the most sustainable biofuels" will be used in the UK. It has no means of enforcing this aim - it admits that if it tried to impose a binding standard it would break world trade rules. But even if "sustainability" could be enforced, what exactly does it mean? You could, for example, ban palm oil from new plantations. This is the most destructive kind of biofuel, driving deforestation in Malaysia and Indonesia. But the ban would change nothing. As Carl Bek-Nielsen, vice chairman of Malaysia's United Plantations Berhad, remarked: "Even if it is another oil that goes into biodiesel, that other oil then needs to be replaced. Either way, there's going to be a vacuum and palm oil can fill that vacuum." The knock-on effects cause the destruction you are trying to avoid. The only sustainable biofuel is recycled waste oil, but the available volumes are tiny.
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お礼
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