Humans often have too much waste, and not enough clean energy. The need to turn one into the other applies both in space, and on the ground. So, inspired by life-support systems for travel to distant planets, NASA has cooked up a low-tech application here on Earth growing biofuel in floating bags of algae.

NASA researcher Jonathan Trent, normally pondering spacecraft systems, created an experiment to feed wastewater from sewage treatment plants into floating plastic bags of algae for biofuels. The bags, composed of the common plastic polyethylene, are filled with fresh water and can float anywhere from saltwater bays to treatment ponds.

Algae is among the most efficient converters of sunlight to energy in the form of oil, but the process to harvest it has been beset with expensive complications: overcrowding, overheating, microbial competition, and other issues that have kept the sector well below commercial volumes for more then a decade.

NASA’s $10 million, two-year project has at least shown that it’s possible for floating plastic bags full of algae and wastewater to yield as much as 2,000 gallons of biofuel per acre annually under favorable conditions. This solves a few problems associated with land-based bioreactors, lowers costs, and takes advantage of open waters to grow the fuel. However, the bags’ integrity in seawater, and their ultimate disposal, remain problematic, as does the system’s economics: NASA is studying whether the numbers will actually support a commercial venture.

For now, NASA seems ready to pass the torch on its larger effort known as the OMEGA project (Offshore Membrane Enclosures for Growing Algae). “The next step,” says NASA on its website, “is for other organizations to deploy larger-scale systems offshore in protected bays to determine if OMEGA can be used commercially for biofuels production, environmental remediation, wastewater treatment or carbon sequestration.”