Global Green Solutions reported on the technique at the AAAS Annual Meeting in San Francisco, US.
The company's Vertigro high-density vertical bioreactors grow algae that use photosynthesis to produce a vegetable oil. This is then refined to make biodiesel.
The company claims its technology can produce up to 180 000 gallons of oil per acre, compared to just 600 gallons per acre for a crop such as the oil palm or 125 gallons per acre for rapeseed. And unlike oil-producing crops, the algae bioreactors can be built on non-arable land and require very little water.
The algae is grown in high-density vertical bioreactors constructed from plastic sheeting. Flow paths formed within the plastic sheeting allow water and algae to circulate constantly through the bioreactors and use the power of sunlight to convert carbon dioxide and water into vegetable oil. The reactors can use carbon dioxide from air, but are much more efficient if using industrial emissions that contain enriched amounts of the greenhouse gas.
"Because our reactors are closed, we can pump in carbon dioxide from industrial flue stacks, thus reducing carbon emissions," says Doug Frater, president of Global Green Solutions. "The demand for bio diesel is growing fast but there is a shortage of feedstock. Using algae to produce feedstock gives very high yields and major environmental benefits."
As well as consuming carbon dioxide, the process of making vegetable oil from algae also produces useful by-products that suit a variety of applications, including solid fuels, feedstocks, fertilisers, nutritional supplements and pharmaceuticals.
Frater admits the idea of using algae is not new. "In the 1970s the US government looked into growing algae in open ponds of water, but this is limited to a thin layer on the surface and open to contamination," he says. "This system is also limited to producing up to 15 000 gallons of oil per acre per year."
There have been multiple attempts at developing bioreactors that provide additional light using fibreoptics or another inserted light source to increase yield. Many of those systems encountered problems with algae attaching to the light source, thus blocking the light from thoroughly penetrating the bioreactor tank. Other algae farm technologies grow algae in plastic bags that are periodically emptied to harvest the algae in a batch process.
Global Green Solutions' Vertigro bioreactor is a closed loop system continuous flow process and is also harvested continuously to give significantly higher yields. The Vertigro system can produce 180,000 gallons (or 4,000 barrels) of oil per acre per year at an estimated cost of $20 per barrel.
"We currently have a pilot plant in El Paso, Texas, US, and hope to be building commercial plants by the end of this year," says Frater. "We hope to have 1000+ acre projects worldwide in 2008."