How a microbial electrolysis cell works

The transportation infrastructure is accountable for 20 percent of all carbon dioxide emissions. This figure can be reduced to zero simply by replacing internal combustion engines—the kind you have in your typical gas-powered automobiles—with hydrogen fuel cell engines.

However, hydrogen fuel cells have been slow to market, primarily due to the high cost of clean hydrogen. Today, researchers at Penn State are developing ways to generate hydrogen at a fraction of the current cost, through the use of common bacteria.

Waste to Energy
Wastewater treatment facilities exist in every country, state and city. These facilities degrade the incoming wastewater so that it can be safely discharged. The key to the degradation lies in the billions of microorganisms in the wastewater.

Just like humans, bacteria extract energy from food to sustain their day-to-day life. The process by which microorganisms eat, called fermentation, inherently breaks down a fraction of the organic matter to hydrogen gas and other organic materials. However, the amount of hydrogen produced typically is not substantial, nor has it been optimized.

What researchers found was that by adding a small amount of electricity (~0.2 volts), these bacteria can degrade substantially more organic waste, which allows for greater hydrogen production. This technology, Microbial Electrolysis Cell (MEC), is similar to water electrolysis, which decomposes water into hydrogen gas and oxygen using electricity.

However, instead of splitting water to create hydrogen, the MEC splits organic matter with the aid of microorganisms. Additionally, the MEC only requires ten percent of the electricity needed for the water electrolysis process.

Thus, through the use of microorganisms, we may be able to finally see a foundation for a hydrogen vehicle infrastructure.

This article is the result of the workshop, "Communicating Your Research to the General Public," presented to the departments of mechanical and nuclear engineering and civil and environmental engineering in August 2011. The author, Marta Hatzell, is a mechanical engineering doctoral student advised by Dr. Bruce Logan, Kappe Professor of Environmental Engineering.

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