Imperium Renewables, which built the largest biodiesel plant in the U.S. at Grays Harbor, gets a lot of flak from protesters who think the Seattle-based company uses palm oil as feedstock – thereby contributing to massive deforestation in Malaysia and Indonesia. The company says it uses canola oil instead, mostly imported from Canada, a crop perceived to be much friendlier to the environment.
But a recent study is casting doubt on canola’s green credentials, too. A group of international scientists concluded that canola-based biodiesel may generate as many or more emissions as its fossil fuel equivalent, The Oregonian reports.
The reason: Fixed nitrogen, used as fertilizer, generates great quantities of nitrous oxide, a greenhouse gas. While previous research has concluded that less than 1 percent of nitrogen fertilizer becomes nitrous oxide, the study’s authors – who include a Nobel Prize winner – say that the percentage is three to five times larger, possibly negating the environmental gains of burning biofuels that originate from feedstock requiring a lot of fertilizer, like canola (also known as rapeseed) and corn.
The report says:
The effect of the high nitrogen content of rapeseed is particularly striking; it offsets
the advantages of a high carbon content and energy density for biodiesel production.
The study does not purport to provide a complete life-cycle analysis of the greenhouse-gas effect of biofuels production, and says that other factors – such as useful byproducts that could fuel crop-growing – could be beneficial to the environment. But it highlights the challenges of controlling global warming, a phenomenon that’s influenced by many factors other than fuel used in transportation.
The report also underscores the promise of cellulosic ethanol, since grasses and forest products do not require much nitrogen fertilizer.