The system is designed to reduce the cost of making fuel from algae by making it possible to put algae farms near wastewater facilities, which offer a large source of nutrients.
But it may prove difficult to implement. For one thing, it will require a lot of plastic. In one possible setup, five square kilometers of plastic bags would be used to produce 2.4 million gallons of algae oil per year—a drop in the bucket compared to the 800 million gallons of oil the U.S. consumes every day. And the bags will likely need to be replaced every year.
The setup has been tested in four nine-meter-long plastic bags at a wastewater plant near San Francisco. The researchers demonstrated that they can grow enough algae to produce nearly 2,000 gallons of fuel per acre per year—if the weather cooperates. So if a commercial system gets built, it may need to be in someplace warmer and sunnier.