Biofuels are not short of fans. Made from crops maize, sugarcane and rapeseed, they make environmentalists happy because they help reduce greenhouse gas emissions by offering an alternative to conventional transport fuels.  But their growing popularity is a cause for concern among African recipients of food aid, most of whom would rather eat maize than see it converted into ethanol.

Over the past three years, venture capital investment in biofuels has increased 800 percent, and the International Energy Agency predicts that production will double by 2011.  In the U.S., for example, this has meant a 300 percent increase in the amount of maize used to produce ethanol since 2001. And Africa itself has increased ethanol production from 100 million gallons in 2006 to over 160 million this year.

All this has some humanitarian aid agencies nervous. While biofuels aren't entirely to blame, they have played a part in pushing up the price of maize across sub-Saharan Africa.  In South Africa, for example, the price of white maize has jumped 186 percent over the past two years, up to $245 per metric ton.  As a result, humanitarian groups can no longer rely on it as a main supplier.  This comes at a tough time for southern Africa: the size of what the UN terms the "food-insecure population" has doubled in South Africa in the past year, and there are food shortages in Swaziland, Zimbabwe and Mozambique. The World Food Programme is now scrambling to procure maize from Malawi, which can offer it for less--around $180 per metric ton.  But if estimates for biofuel demands are accurate, Malawian prices won't stay low for long.