Study: Pros and Cons of Algae Biofuel

Posted by Jared Killeen on January 26, 2010 at 10:17 am

One of many methods of growing algae. (image: Paul Francis Harrison via flickr.com)

A recent study published in Environmental Science and Technology proposes that algae-based biofuel might not be as environmentally friendly as is commonly believed. The problem is not with burning it, but with growing it: because algae production requires fertilizers, which emit nitrous oxide (a greenhouse gas), algae-based biofuel can end up producing more pollution than it absorbs.

While corn and switchgrass can draw nitrogen from soil, which reduces the amount of fertilizer needed, algae requires that additional fertilizer be added to the water in which it grows. “Nutrients are going to be the limiting factor,” said Dr. Andres Clarens, an Assistant Professor of civil engineering at the University of Virginia and an author of the study. “We’re humans. We need to eat dinner, and you can’t expect to have algae that provide a bunch of energy without feeding it nutrients.”

However, there are still several benefits that recommend algae over soil-based biofuels. For starters, algae grow atop water and do not compete with food crops for land space. Also, they have a higher energy yield than other biofuels, including corn and switchgrass. Such qualities have led some scientists to extol algae as the most promising of biofuels and the future of global energy.

Moreover, scientists have suggested a clever way of producing algae without using tons of fertilizer. Because algae can grow pretty much anywhere, or in anything, producers like Simply Green Biofuels have considered channeling municipal wastewater into algae plantations. The nitrogen-and-phosphorous-rich sewage would provide the growing algae with all the nutrients it needs. At least some fuel companies think this system will work: last summer, energy ExxonMobil devoted $600 million to the project.