Today's entry into the top 5 biofuels sweepstakes is rapeseed. This mustard green is also known as oilseed and canola. Though it is indeed a leafy green, it's largely grown for its seeds, which are about 40 percent oil. China and Europe produce most it, to the tune of about 47 million tons per year in total.
Rapeseed has been used for making soap, oils and plastics manufacturing, but it really shines as a biofuel. In fact, Europe is the leader in making biodiesel from rapeseed oil. Why? Mainly because they heavily subsidize the stuff in Europe, much like the United States does with corn. The EU wants to have 10 percent of its vehicles running on biodiesel by the year 2020 and rapeseed looks to be a major player.
Right now, producing rapeseed biodiesel is about two to three times as expensive as producing traditional petroleum, so there's clearly some work to be done on this front. But it's good enough to end up as our number four biofuel.