Biodiesel: cultivating alternative fuels

Environmental Health Perspectives, Feb, 2007 by Charles W. Schmidt

Food for Fuel

Biodiesel's rapid expansion--combined with that of other biofuels such as ethanol--has led some to worry that fuel generation could divert agriculture from food, leaving some people hungry. Margarine manufacturers in Germany and France, where nearly 860 million gallons of biodiesel were produced in 2005, already complain they're being sidelined by crop diversions to the fuel industry. Could that signal a more dramatic competition to come as biodiesel production accelerates?

Most experts say no. Grant Kimberley, who directs market development for the Iowa Soybean Association, says that in the United States, the soybean oil used for biodiesel so far comes from existing surpluses, meaning the industry hasn't diverted any oil into the fuel market yet. And Jobe emphasizes that by making soybean oil more valuable, biodiesel production lessens the pressure on solid soy meal (the portion with the protein) to generate dollars for the industry. "And that will allow farmers to get more money for the whole bean while driving down the cost of meal that generates protein for livestock feed," he says. "The only people who might go hungry are those who subsist on french fries, margarine, and Italian dressing."

Moreover, experts anticipate that future biodiesel feedstocks will generate higher oil yields than soybeans. Whereas soybeans yield 18-20% oil, other crops produce much more; the oil yield from canola, for instance, tops 40%. Jake Stewart, vice president for strategic development at Organic Fuels, a Houston, Texas-based refinery that made 30 million gallons of biodiesel in 2006 (making it the largest producer in Texas and the third largest producer in the United States), says the industry has barely scratched the potential when it comes to higher-yield crops.

While declining to speak specifically about his company's leanings in this area, Stewart suggests the industry will look to completely different species with higher oil yields, such as shrub trees. The biggest contender of all, Stewart says, is algae, which has an oil yield of up to 50%. "That's the only feedstock with the potential to really displace petroleum in this country," he says. Whereas soybeans generate roughly 50 gallons of biodiesel per acre, algal species can produce up to 8,000 gallons per acre per year, according to Michael Briggs, a PhD candidate in physics who investigates biodiesel production at the University of New Hampshire. This makes them the most promising potential feedstock by far.

The trick is to somehow grow algae in systems that allow producers to control production. Open ponds are problematic, says Briggs, because it's hard to control species distribution. To make a uniform product, manufacturers need a system that grows just one selected species, without infiltration by others.

Briggs says the favored approach employs closed bioreactors that keep unwanted species out while allowing for precise control of light, water quality, and nutrient inputs. In one blue-sky scenario, producers could install bioreactors throughout the country and grow algae with nutrients obtained from wastewater treatment facilities, he says. A total of 15,000 square miles, equal to about 12.5% of the area occupied by the Sonora Desert, could generate 140 billion gallons of biodiesel--enough to replace nearly all the petroleum used for transportation in the United States today (assuming gas-driven cars switched to diesel technology).