Scientific American:Is Algae Worse than Corn for Biofuels?

"Is Algae Worse than Corn for Biofuels?A new analysis suggests so because of the need for copious fertilizer"
http://www.scientificamerican.com/article.cfm?id=algae-biofuel-growth-environmental-impact
Fertilizers come directly from fossil fuels so in this light:
"Interest in algae-based biofuels has blossomed in the past year, sparking major investments from Exxon Mobil Corp. and Dow Chemical Co., and it has gained steam on Capitol Hill, as well."
Also from same article:
The culprit, the researchers say, is fertilizer. Growing algae in open ponds is akin to producing them in a shallow swimming pool, Clarens said, so all of the nutrients -- nitrogen and phosphorus -- needed to keep them alive and boost their production come from outside sources.

And that fertilizer has an environmental impact because it's often made from petroleum feedstocks, Clarens said.

"If you grow corn, you rotate the field with soybeans so you get nitrogen fixation," Clarens said. "You still have to fertilize a lot, but if you're growing algae ... all that fertilizer has to come from you, and the fertilizing demands are much higher."

"Trees cause more pollution than automobiles." Ronald Reagan