Interesting, but as with all of these studies, the assumptions made by the authors can drastically alter the result. Without more information about their methodology etc it is hard to comment on it, but regardless, this article is definitely worth a read:
Biodiesel could increase rather than reduce greenhouse emissions compared to conventional diesel, says analysts at SRI Consulting, a chemical business research firm. They also cited that â€œEU 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 dieselâ€, in a new study reported in Chemistry & Industry, the magazine of the SCI.
The analysts have compared the emissions of greenhouse gases by the two fuels across their overall life cycles from production to combustion in cars. The results showed 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.
However, 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, SRI Consulting said.
Petroleum diesel emits 85% of its greenhouse gases at the final stage, when burnt in the engine. By contrast, two-thirds of the emissions produced by rapeseed derived biodiesel (RME) occur during farming of the crop, when cropland emits nitrous oxide (N2O), otherwise known as laughing gas, that is 200-300x as potent a greenhouse gas as CO2, according to the study.