Fruits of the forests?

Biofuels. They’ve got to be a good thing, right? You’re not getting hydrocarbons from the ground, you’re getting them from crops, so there are no greenhouse gas emissions to worry about and you can fill your petrol tank and drive with a clear conscience.

Right?

Well, no.

A United Nations report has now summarised many of the concerns over biofuels. The problem is that they’re an agricultural product, and the demand for fuel is so high that they could lead to a rapid increase in intensive farming. Land used to grow sugar cane or oilseed rape for fuels can’t be used to grow food, leading to price rises that could be crippling for poorer countries. Famine is a real concern, as there just isn’t enough land to farm animals and crops for food, and to raise crops for fuel-making.

And there are other risks. In the tropics, there are already concerns that demand for palm oil — a particularly useful starting material for biofuels — is leading to the destruction of rainforest for palm plantations, which are less efficient at absorbing CO_². Production of biofuel under these conditions could lead to the emission of even more greenhouse gases than burning fossil fuels. There are also concerns over loss of biodiversity, soil erosion, and water usage.

It’s enough to make the environmentally-concerned motorist throw up his hands in despair and consider swapping that SUV for a mountain-bike after all. But, as in so many cases, there’s a role for the engineering community here.

Many of the concerns over biofuels apply only to what’s called ‘generation one’ of the technology. Generation two biofuels are made from agricultural wastes — wood chips from the timber industry, the stalks and leaves from maize, the chewed-up fibres from sugar cane. Theoretically, with these products, food production and biofuel production can live together without increased pressure on land use.

It’s not that simple, of course; development on G2 biofuels is at a relatively early stage, and the reactions to transform agri-waste into diesel are too slow to be commercially viable. The engineering communities still need to do a great deal of work, and public funds might well be needed.

In the meantime, it might be best to heed the UN’s words on this. Biomass is probably best suited for combined heat and power, it says. Fuels from crops can keep the lights on, but they can’t make the wheels go round.

Stuart Nathan