英文议论文素材大全——生物能源的利与弊

Pros Cons

Biofuels are the best way of reducing our emissions of carbon dioxide and other greenhouse gases responsible for global climate change. As with fossil fuels, burning biodiesel or ethanol to drive an engine or generate electricity releases carbon into the atmosphere. Unlike with fossil fuels, however, growing the plants from which biofuels are made takes carbon from the air, so overall the process is carbon neutral. This means policies to increase the use of biofuels could greatly reduce overall levels of carbon emissions, and so be a major part of tackling global climate change. They can also help improve local air quality as mixing ethanol with fossil fuels helps meet clean air standards. In theory biofuels appear to reduce overall carbon emissions, but in practice they are much less environmentally friendly than their boosters claim. Although growing plants absorb carbon from the atmosphere, the whole process of turning a seed into fuel is very energy-intensive. Modern farming uses large inputs of fertilisers, as well as fuel for running machinery and transport. Turning a crop into biofuel that can be used in an engine also requires a lot of energy. All of this produces additional carbon emissions and means that biofuels are often not much better for the atmosphere than the fossil fuels they seek to replace, especially as more fuel needs to be burned to travel the same distance (because they are less efficient than fossil fuels). Some biofuel crops (e.g. sugar cane) do produce much more energy than is needed to grow them, but making ethanol from maize may actually take 30% more energy than it generates as a fuel – and it is maize-based ethanol that US policy is backing so heavily.

Unlike oil, biofuels are renewable and sustainable. At present mankind is using up fossil fuel resources at an alarming rate, and often damaging the environment in order to extract them. If we go on relying on fossil fuels they will one day run out, and not only will our descendants no longer have viable energy reserves, but they will also have to cope with the ecological damage coal, oil and gas extraction have inflicted on the earth. Making fuel from crops provides a perfect, sustainable solution. The increased production of biofuels presents a growing environmental threat. If biofuels are to meet a significant part of our energy needs, vast areas will need to be devoted to crops such as oilseed rape, maize, sugar cane and oil palms. These monocultures are very bad for biodiversity, denying wildlife and native plants places to live. And as the crops will not be grown for human consumption, it is likely that there will be greater use of pesticides, herbicides and

genetically-modified crops – all very bad for the natural environment. The greatest environmental threat will be in the developing world, where profits from biofuel production provide strong incentives to cut down the remaining rainforest areas to create sugar cane or palm oil plantations – a process which can already be seen in Brazil and Indonesia.

There is plenty of scope to produce much greater quantities of biofuels without squeezing food production. Many developed countries have been overproducing crops such as wheat in past decades, leading to programmes such as the EU’s set-aside scheme whereby farmers are paid not to grow crops on some of their land. Agricultural productivity continues to rise, especially in the developing world where new techniques and strains of seed, including types

genetically-modified to suit harsh conditions will Using agricultural land to grow biofuel crops means that less crops are grown for human consumption (or for feeding livestock). This pushes up the price of food for everyone but especially affects the poor, both in developed countries and in the developing world. Already Mexicans have found the price of their staple tortillas has risen sharply, as American maize is diverted to subsidised biofuel plants in the Mid West. The prices of sugar and palm oil have also experienced steep increases recently. If biofuel