Last year, Frogblog blogged about GreenFuel, an American company working on using algae farms to reduce greenhouse gas emissions from power plants. Exhaust gases from burning coal, natural gas or whatever are piped through an array of tubes containing a fast-growing green algae, which strip out up to 40% of CO2 and 86% of NO2. The algae can then be processed into biodiesel and bioethanol, sold at a profit, and used as transport fuel. While this is simply delaying the original emissions from the power-plant, if these biofuels displace fossil fuels, then the result is a real reduction in emissions.
Berzin [Greenfuels' founder] calculates that just one 1,000 megawatt power plant using his system could produce more than 40 million gallons of biodiesel and 50 million gallons of ethanol a year. That would require a 2,000-acre "farm" of algae-filled tubes near the power plant.
The US has about a thousand power plants of this size. New Zealand has only one, at Huntly. By my back-of-the-envelope calculations, and working around the archaic American units, installing such a system there would produce enough biofuels to meet about 5% of our demand for petrol and diesel in one go. Similar systems at our major gas-fired power plants (at Southdown, Otahuhu B and New Plymouth) could produce roughly another 3%. That's not enough to solve our greenhouse gas problem, of course - but it would be a big hole in it, and help set us on a path to greater sustainability.
As useful as it sounds, the real prize with this technology isn't scrubbing emissions from power plants with biofuels as a byproduct, but primary biofuels production. This snippet gives an idea of the possibilities:
One key is selecting an algae with a high oil density - about 50 percent of its weight. Because this kind of algae also grows so fast, it can produce 15,000 gallons [around 55,000 L] of biodiesel per acre. Just 60 gallons are produced from soybeans, which along with corn are the major biodiesel crops today.
At that rate, it would take less than 200 square kilometers of algae farms to substitute for our entire annual diesel consumption - or about 1% of our current land used for permanant crops.
The technology is still in its experimental stages - the first full test on a 1000 MW power station is scheduled for next year - but in the long-term this looks like an excellent way of reducing our overall emissions and moving to a sustainable economy. All we have to do is adopt it...