Pond scum isn't usually something intentionally cultivated, as its overgrowth in surface waters because of excess agricultural fertilizer runoff—aka algae blooms—can be toxic to marine life. However, this algae’s potential as a source for next-generation biofuels, not to mention its ability to clean pollutants from brackish water, has scientists actively growing microalgae and working to extract the lipid content on a scale that could eventually be economically viable.
One such algae biofuel project is looking to turn the Salton Sea, one of California’s most polluted lakes thanks to high levels of nitrogen and phosphorus from fertilizer runoff, into a virtual scum farm that could be responsible for cleaning up that body of water while also producing a low-impact biofuel feedstock. The Salton Sea Biomass Remediation Project (SABRE), which is funded by the Department of Energy’s Bioenergy Technology Office (BETO), is currently using solar power to slowly pump water through a 900-foot (274-meter) “Algal Turf Scrubber” raceway. Inside, native algae species growing in the system consume the excess nutrients and return clean water to the local wetland. The algae is then harvested and sent to Sandia National Laboratories, where biochemists are working to develop effective and economical methods of extracting biofuel from the pond scum.