A Green Scrub

Algae tumbling in plastic tubing on the roof of MIT’s cogeneration power plant are helping to make the Institute greener. Cambridge, MA-based GreenFuel Technologies is using the plant as a test bed for its smog-reducing system, which connects tubes filled with algae that eat nitrogen oxides—a major contributor to smog—and carbon dioxide to part of the plant’s emission stream. Each day, the feeding algae remove more than a third of the pollutants that pass through the tubing. A device that controls how quickly fluids move through the system manages the algae’s growth by tempering their exposure to light. Still, the algae grow quickly, so GreenFuel technicians remove some daily and replace them with salt water and nutrients, giving the remaining algae room to grow. The harvested algae can then be used to make fuels, plastics, or food products.

GreenFuel is enthusiastic about the system for several reasons. The process can be tailored to a specific plant through the selection of the algae species best suited for the type of gases emitted and the amount of natural light available. The system is also much cheaper than any available technology for nitrogen oxide emissions reduction and may be the only economically viable process available to cut carbon dioxide at the source.

MIT is delighted to be part of the project, says Peter Cooper ’70, MIT’s director of utilities. “We’re just pleased to help GreenFuel prove its technology and to bask in any reflected glory,” he says. If the test at MIT is successful, GreenFuel will bring its smog-reducing contraptions to the wider world.