ALGAE are being put to work performing a unique double duty: cleaning up sewage waste while simultaneously producing biofuel.
All algae feast on phosphates and nitrogen-containing compounds, converting them to lipids. Some of these oils can be converted to biofuel, but only a few algal species produce lipids of the right type and quantity to be easily converted to fuel. In theory, though, algae are a perfect renewable fuel source. The main obstacle is that brewing the right nutrient mix can be prohibitively expensive.
Now, in work for a master's thesis, Eric Lannan, a mechanical engineer at Rochester Institute of Technology (RIT) in New York and colleagues have identified three types of microalgae - Scenedesmus, Chlorella andChlamydomonas - that efficiently convert nutrients to fuel on a diet of municipal waste water, while happily living in its harsh, salty environment. In a lab test, it took just three days for the algae to gobble up 99 per cent of the ammonia, 88 per cent of the nitrate and 99 per cent of the phosphates in a broth resembling that from a domestic sewage treatment plant, turning themselves into rich sources of fuel even as they purified the water.
"People had looked at algae to clean waste water, others to make biodiesel," Lannan says. "We're putting those ideas together."