The world's farmers are rapidly moving from their traditional products - food, feedstock and fibre - to producing vehicle fuel. Simple logic says that making fuels from crops can save lethal greenhouse gas (ghgs) emissions - the CO2 released in burning the fuels is absorbed from the atmosphere by next year's growing crops (the carbon cycle).

The world's farmers are rapidly moving from their traditional products - food, feedstock and fibre - to producing vehicle fuel. Simple logic says that making fuels from crops can save lethal greenhouse gas (ghgs) emissions - the CO2 released in burning the fuels is absorbed from the atmosphere by next year's growing crops (the carbon cycle). But is this really right?

Well, increasingly environmentalists are concerned by the huge changes being made to agriculture and the biosphere across the globe, and no one really knows if biofuels make net savings or losses of energy and carbon emissions when their whole production lifecycle is evaluated.

This is hotly debated, and even "pro camp" research doesn't look good - a 2002 US Department of Agriculture report found that for every gallon of ethanol, the equivalent 0.92 gallons of fossil fuels was needed for its production. This year a much hyped paper in Science magazine found production was only "net energy positive" when co-products such as cattle feed were included. Some scientists contest even these modest fossil fuel savings asserting that, in a more complete analysis, no biofuel has a positive energy balance.

Why? Energy inputs for mega-scale production include petroleum-based herbicides, pesticides, and fertilisers, and fossil-fuelled tractors and trucks plough the fields, harvest the crop, and ship the crop to the fuel refineries. In the case of the US ethanol industry, the fossil-fuelled trucks ship the fuel halfway across the country from the population sparse corn belt to population and car dense states like California and Texas. Biorefineries are themselves fired by fossil-fuels in enormous quantities to ferment, and then purify ethanol from the watery fermentation product.

Can we trust this industry, based on disputed science, as it rapidly grows, driven by very powerful vested interests? Do they care about the eco-system, when they throw caution to the wind at the whiff of profit?

Rapid growth must concern us - current global production is over 12 billion gallons, nearly tripled since 2000. It is set to triple again by 2012 with Brazil and the US leading. There is now a global agro-chemical-biotech-oil industry based around refineries producing millions of gallons of fuel product per annum, and commodity markets trading billions of tonnes of corn, soya, sugar, wheat and oil palm per annum. Worldwide vast new areas of GM soya, sugar, maize, sorghum, sunflower and rape seeds are planted as bio-refineries spring up.

This is already forcing food and fuel producers to compete for the same crops. After a 20pc rise in corn prices (April/May 2006), the Financial Times reported US farmers are diverting more of their harvests towards producing fuel rather than food or feedstock for animals. Lester Brown, the director of the Earth Policy Institute, is quoted: "Service stations are now competing directly with supermarkets for food commodities".

Such food-fuel competition could be devastating in an unregulated market - countries in the global South may devote ever-expanding areas of cash crops for vehicle fuels, displacing local food production and decimating the livelihoods of small farmers and local people. Soon food prices and supply could become subsidiary to the global energy market - wealthy western car drivers literally pitted against hungry consumers in developing countries.

Environmental damage is rife as enormous areas of forests are displaced for crops, releasing huge amounts of greenhouse gasses with untold loss to wildlife and entire species. We can also expect vast monoculture and constant cropping to deplete soil and destroy biodiversity, whilst production and manufacture requiring huge amounts of water will deplete water supplies.

All this leads to the sad conclusion that large scale biofuels production is an extremely energy intensive, CO2-emitting and polluting process causing rapid damage through its growth.

Can we make better use of the carbon cycle? Yes, if we develop biomass for heating and power instead of vehicle fuels. This is efficient in energy and CO2 savings in local small and medium scale energy plants (tinyurl.com/j4a8d). It has been shown that such biomass power on a decentralised grid could ensure our energy security within 20 years without any new nuclear build (see tinyurl.com/zohwr).

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