carbon limited

Biofuel is all over the news right now. The recent agreement between US and Brazil, Al Gore’s presentation at the World Biofuels Conference, and the latest UK budget are just a few examples. At first glance biofuels promise to be a key element in a sound strategy to mitigate climate change. But under the surface rages a fierce debate.

In order to be successful, biofuels must have a positive energy balance (i.e. they must result in more useful energy than is required to cultivate and process the feed stocks) and they must result in lower carbon emissions than their fossil fuel counterparts.

In temperate zones, land already under the plough might produce feed stocks with lower carbon than fossil fuel diesel. But recent papers have found that these fuels are net energy losers (see links at end).

Some of the best energy returns are achieved from palm oil plantations grown on deforested land in the tropics. But because of the impact of change of land use, the carbon emissions associated with the resulting biofuel have been estimated to be more than eight times that of the equivalent fossil fuel diesel.

Certainly biomass has an important role to play in reducing the impact of climate change. Organic waste streams can be a valuable resource for producing cellulosic ethanol. Wood waste and biomass crops can provide fuel for low carbon heat. But instead of helping to reduce CO2 and dependence on fossil fuel, large scale cultivation of feed stock for the production of ethanol may only be an efficient means of subsidising agribusiness in the developed world and making a profit through the exploitation of labour and natural resources in the developing world.

This isn’t my area of expertise so that’s it from me. But here are some sources I came across while trying to find out more (many thanks to Almuth at Biofuel Watch for his assistance and emails):

The Sarasin Bank issued their report in the summer of 2006, Biofuels–Transporting Us to a Fossil-Free Future?, in which they place the present limit for the environmentally and socially responsible use of biofuels at roughly 5 percent of current petrol and diesel consumption in the EU and US. Here’s a summary.

A paper by Tad Patzek, a professor at UC Berkeley’s Department of Civil and Environmental Engineering, on the negative energy balance of corn ethanol

Much of the debate on ethanol production on existing farms in the developed world centres on how much carbon and energy credit you give yourself for the use of by-products. Here is another paper by Patzek with discussion on this topic.

Here is an article from Science Vol 311, Jan 27 2006 in which Alexander Farrell and co-authors suggest that corn ethanol has a positive energy balance. This provoked a strong response in the subsequent letters page of Science.