Biofuels are a Bummer

Here’s a summary of a piece in a recent ScienceDaily that reports an April 2007 study by SRI Consulting. An oldie but goodie.

EU legislation to promote the uptake of biodiesel will not make any difference to global warming, and could potentially result in greater emissions of greenhouse gases than from conventional petroleum-derived diesel.

Here’s the picture. Transportation accounts for more than a fifth of all greenhouse gas emissions emitted in the EU, and the 2003 EU Biofuels Directive aims to increase the levels of biofuels to 5.75% of all transport fuels by 2010, up from roughly 2% currently. This will be further increased to a 10% share in 2010, the Commission announced in January this year (2007). It is expected to help meet the EU's Kyoto commitment to reduce levels of greenhouse gas emissions by 8% by 2012 relative to 1990 levels, and by 20% by 2020.

Rapeseed-derived biodiesel is the major renewables-derived biofuel used across Europe. However, the results of the study show that biodiesel derived from rapeseed grown on dedicated farmland emits nearly the same amount of greenhouse gas emissions (defined as CO2 equivalents) per km driven as does conventional diesel. But there’s more to the story. Petroleum diesel emits 85% of its greenhouse gases at the final stage—when burnt in the engine—but 2/3 of the emissions produced by rapeseed-derived biodiesel occur during farming of the crop, when cropland emits nitrous oxide (N2O), otherwise known as laughing gas. And N2O is 200-300 times as potent a greenhouse gas as CO2! If the land used to grow rapeseed was instead used to grow trees, petroleum diesel would emit only a third of the CO2 equivalent emissions as biodiesel.