State of the Planet

News from the Columbia Climate School

A Renewing Interest in Energy

Common Soil
Common soil in which Bacillus Subtilis can be found. Photo: Juandev

By Lazaro Dubrocq

Should Ozgur Sahin, associate professor of biological sciences and physics of Columbia University, continue expanding upon his work in researching how the tiny movements of microbes can be harnessed to create electrical and mechanical energy, it may pave the way for a world fueled in part by bacterial spores.

Basing his research on the common bacteria Bacillus, specifically the Bacillus Subtilis, which are found in the soil, Sahin has found a way to utilize a specialized behavior of the bacteria to achieve a relatively large amount of usable energy. When deprived of food or water, Bacillus shrinks and forms a rigid dormant spore as a survival mechanism to protect its genetic material, similar to a grape shrinking to a raisin under sunlight. In humid conditions, the spore absorbs moisture to expand dramatically; the opposite occurs in dry conditions. Sahin and his fellow researches theorized that in order for the bacterium to accomplish this, it had to be storing great amounts of energy.

As Sahin explained in his publication in Nature Nanotechnology, “changing size this much is highly unusual for a material that is as rigid as wood or plastic. We figured that expanding and contracting spores can act like a muscle, pushing and pulling other objects. We noticed that we could harness the motion of spores and convert it to electrical energy.”

Bacillus Subtilis. Photo: CDC/ Dr. William A. Clark

“The biggest power source in nature is evaporation,” Sahin said. “Our climate is powered by evaporating water from the oceans, and we have no way of accessing this energy.” No way until now, perhaps.

Sahin built a prototype generator modeled after a wind turbine. Using this prototype, Sahin demonstrated that the energy from the spore’s movements could be harnessed and utilized as expendable energy.

The fundamental idea is rather simple: the researchers apply a thin layer of spores to a flexible, elastic rubber sheet and connects it to a turbine generator. The expansion and contraction of the bacteria bend the sheet, creating mechanical energy that can be converted into electrical energy. This video simulates the process. Sahin could also utilized a spore-coated rubber as an cantilever that would drive a magnet to produce electricity.

The potential industrial use for these spores could be widespread. The simple process of attaching the spores to a sheet and harvesting the movement as energy could be of use to large energy-dependent industries such as electrical production. Sahin compares the energy output to that of solar energy. The spores have been shown to be able to produce up to 1,000 times more force than the human muscle with only a small amount of moisture needed to activate the mechanism.

Sahin hopes that his research could eventually lead to the development of a battery to harness and store this energy from the spores. The U.S. Department of Energy is currently supporting further research to study the energy output of the movement within the sheet, as well building new types of material so that the spores can be applied to much larger structures.

Using this technology, Sahin hopes that “this may be an opening for a completely new energy platform.”

Lazaro Dubrocq is a sophomore studying chemical engineering at Columbia University, and currently interning for the Earth Institute Center for Environmental Sustainability.

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