By David L. Brown
A company in Massachusetts, GreenFuel Technologies Corp., is developing a process through which CO2 generated in power plants can be captured and used to grow algae, which in turn can be processed into various forms of fuels including biodiesel and ethanol. The system is designed to be retrofitted to existing power plants, thus helping both to mitigate future emissions of greenhouse gas and to provide an alternative source of energy.
An article in New Scientist magazine (6 October, 2006) describes the process:
Two of the world’s greatest energy users are electricity generation and transport. Both are responsible for huge quantities of greenhouse gas emissions, as most power plants and vehicles still rely on fossil fuels. Now GreenFuel and others are hoping to marry the two together with an emerging technology that uses a by-product of one to supply fuel to the other. Doing so could dramatically reduce their overall carbon dioxide emissions.
At the heart of the technology is a plastic cylinder full of algae, which literally sucks the CO2 out of a power plant’s exhaust. The algae can in turn be converted into biofuel, creating a cycle that takes the carbon from the smokestack to the gas tank before it enters the atmosphere.
If successful, the technology could capture all of a power plant’s CO2 emissions. “Right now, when you say CO2, people want to hide under the table. Carbon dioxide is not something you want to pump underground, it’s something you want to reuse,” says [Isaac] Berzin [the company’s founder and chief technical officer].
According to the company’s website, its patented Emissions-to-Biofuels™ (E2B™) process “harnesses photosynthesis to grow algae, capture CO2 and produce high-energy biomass. Using commercially available technology, the algae can be economically converted to solid fuel, methane, or liquid transportation fuels such as biodiesel and ethanol.” The entry continues:
Building on many years of work sponsored by the DOE and international agencies, GFT installed its first field unit on a 20 MW cogeneration facility at the Massachusetts Institute of Technology in 2004. Its second, larger unit was commissioned at a 1,060 MW combined cycle facility in 2005 in the southwest United States. The bioreactor productivities suggest annual yields of 5,000-10,000 gallons of biodiesel and a comparable amount of bioethanol per acre.
The company posted this diagram showing how the process could work:
The New Scientist article also discusses other efforts in a similar vein:
Although ahead of the competition in terms of developing prototype bioreactors, GreenFuel is not the first to use algae to produce samples of biofuel from power plant exhaust. In March Laurenz Thomsen and his team at the Greenhouse Gas Mitigation Project at the International University Bremen in Germany used microalgae to produce 10 millilitres of biodiesel. Thomsen is now working on a possible joint venture with GreenFuel to develop algae farms at CO2-belching coal-fired plants in eastern Europe.
“Using technology based mainly on GreenFuel, we can mitigate 50,000 tonnes of CO2 per square kilometre per year,” he says. Building a 1-square-kilometre facility would cost approximately $20 million, he estimates, but the payoffs would be equally large. “I think we are close to the point where we can gain $5 to $10 million a year by selling the fuel.”
Another company building a pilot algae reactor is New York-based GreenShift. The company plans to begin testing its reactor at a bioethanol plant in Iowa in early 2007, where waste CO2 is emitted when corn is converted into ethanol. “Roughly one-third of the corn that goes into a facility comes out as ethanol,” says Kevin Kreisler of Greenshift. “With algae and other technologies we can increase that to two-thirds.” Like GreenFuel, the company eventually plans to use the technology at power plants.
Instead of exposing the algae directly to sunlight, Greenshift uses an array of mirrored troughs and fibre optics to carry sunlight to the plants. Algae don’t need strong sunlight for photosynthesis, so the bioreactors could feasibly be housed in buildings or underground. “It’s all about efficiency,” says Kreisler. “By diffusing the light we can take one square metre of sunlight and spread it out over 10 square metres of growth plates, thus reducing the amount of land we need by a factor of 10.”
Such technologies may seem far-fetched, but the clear benefit of this system is its potential to capture and recycle carbon dioxide as we continue to burn fossil fuels, while providing an alternative to petroleum. The downside of this is that when the biofuels are burned they in turn will emit CO2 into the atmosphere, so the first problem will not actually be solved, but will put the emissions to good use as we search for better solutions. In the longer term, we must develop renewable non-polluting energy sources if we are to have any hope of mitigating climate change. That will involve systems that either do not emit greenhouse gases, or which use processes that convert them permanently into materials that are not harmful to the environment or to sequester them in some way.