Electricity from Living Plants – “Green Electricity” from Your Food Garden
Plant-e technology – Produce food on your roof and charge your cell phone at the same time
Plugging in to Plant Roots- Marsh grasses can power small fuel cells
By Lucas Laursen
Cast-off electrons in a plant’s roots can provide electricity, a Dutch team reports. Now, through a spin-off company, it hopes to grow grassy generators on rooftops and promote decentralized electrical production in wetlands in developing countries.
Plants exude a variety of waste products that microbes consume, such as glucose, acetate, butyrate, and propionate. The underground interaction leaves spare electrons in the surrounding soil and water, which researchers—led by Bert Hamelers at Wageningen University, in the Netherlands—began tapping in experiments in 2007. They were already working on using so-called microbial fuel cells (MFCs) to treat wastewater when they realized that plant roots improved the performance of the fuel cells.
In a series of experiments, the team measured the performance of its fuel cells as used in conjunction with plants. When bacteria consume a plant’s organic waste, they release electrons, carbon dioxide, and hydrogen ions. The plant-microbial fuel cell passes the ions—but not the electrons—through a membrane to an oxygen-rich cathode, creating a potential difference. Wageningen environmental technologist Marjolein Helder and her colleagues built a pilot plant on the roof of a building at the university that has produced an average of about 0.44 watts per square meter of planted area, which they reported in the January/February issue of Biofuels, Bioproducts, and Biorefining. “With the power output we’ve achieved, we don’t have an economically practical green electricity technology…but we’ll definitely be able to compete soon,” Helder says.
See a small globe spin using plant electricity. “Plant-e planet makes the world go round”.
She’s comparing the plant-microbial fuel cell to other biomass energy technologies, such as growing trees and burning the wood or fermenting waste biomass into a liquid fuel. The amount of energy per unit land area the team has achieved is already the same order of magnitude as that of at least one estimate of old-fashioned wood-burning, of about 0.7 W/m2. The advantage of plant-MFCs is that although they’ll require occasional maintenance, they won’t require harvesting or transporting wood.