With an inexpensive method of sewage treatment, NASA's Ames Research Center in California is researching to produce algae-based fuel by growing algae in plastic bags of sewage floating in the ocean.
The lead researcher on this project, Jonathan Trent mentioned that the research effort aims at:
(i) Producing biofuels utilizing few resources in a confined area,
(ii) Cleansing municipal wastewater, and
(iii) Sequestration of greenhouse gas emissions produced during the process.
"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 starts by firstly putting the algae in plastic bags filled with sewage having an acronym called OMEGA. These offshore membrane enclosures allow the freshwater exit but prevent saltwater from moving in. Then the algae start feeding on the nutrients in the sewage. The floating OMEGA bags utilize water, solar energy and carbon dioxide, absorbed through the plastic membrane to produce sugar. In the process of feeding, the algae clean up the water and metabolize sugar produced into lipids that will be used later as fuel. The Oxygen and cleansed water are then released through the membrane to the ocean.
After the process is finished, the plastic OMEGA Bags could be recycled as plastic mulch or chopped and used to improve soil quality and help retain moisture.
"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."
Feasibility
"We don't think this would be cost-effective if we just go after the fuels," Trent said. "But we're functioning on at least three different levels: making the products -- fuel, fertilizers -- then wastewater processing and carbon sequestration. The economic model becomes more reasonable."
"We've solved the problem of evaporation, weeds, structure," Trent said. "And we think we've added other benefits like processing sewage and sequestering carbon."
"It seems huge, but it's a small area in the overall oceans," he said. "And we imagine [the OMEGAs] distributed around, locally distributed ... or franchised and monitored by fishermen."
Hurdles
The researchers are still trying to find plastic capable of withstanding pounding waves and cold temperatures without becoming too brittle for osmosis.
"On a planet with a population growing at exponential rates and resources dwindling, we're almost in a state of emergency on a timeline measured in decades," Trent said. "I think it's important, this process of coming up with alternatives. ... I don't know if OMEGA is the solution, but it's something that should be carefully scrutinized."