NASA is applying space technology to a decidedly down-to-earth effort that links the production of algae-based fuel with an inexpensive method of sewage treatment.
The space agency is growing algae for biofuel in plastic bags of sewage floating in the ocean.
Jonathan Trent, the lead researcher on the project at NASA's Ames Research Center in California, said the effort has three goals: Produce biofuels with few resources in a confined area, help cleanse municipal wastewater, and sequester emissions of the greenhouse gas carbon dioxide that are produced along the way.
"Algae are the best source of biofuels on the planet that we know about," Trent said in an interview. "If we can also clean [wastewater] at the same time we create biofuels, that would great."
The process is amazingly simple. It starts with algae being placed in sewage-filled plastic bags, which in true NASA style have a nifty acronym, OMEGA, for "offshore membrane enclosures for growing algae."
The OMEGA bags are semipermeable membranes that NASA developed to recycle astronauts' wastewater on long space missions. In this case, the membranes let freshwater exit but prevent saltwater from moving in.
Then the algae in the bag feast on nutrients in the sewage. The plants clean up the water and produce lipids – fat-soluble molecules – that will be used later as fuel.
Just as in algae biofuel production on land, the floating OMEGA bags use water, solar energy and carbon dioxide – which in this case is absorbed through the plastic membrane – to produce sugar that algae metabolize into lipids.
Oxygen and fresh, cleansed water are then released through the membrane to the ocean.
"It's energy-free," Trent said. "It doesn't cost us anything. Osmosis works by itself."
The system is foolproof, he said. Even if the OMEGA bags leak, the salty ocean water would kill the algae, preventing the escape of an invasive species.
"Freshwater algae can't compete in the marine environment," Trent said. "We're not putting something out there that could become an invasive species."
And if the wastewater spills, he said, "the only thing we're putting in the water is already in the ocean anyway."