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A Potential Energy Source, All Around Us

Cities across the U.S. could soon harvest their own concentrated, energy-rich biomass and generate low-cost electricity.

Stefanie Kring, a Clarkson doctoral student in environmental science and engineering, studies the pools where used water is treated and she found something significant.

“Wastewater lagoons are full of zooplankton,” she says. “These are the same types of organisms we see in lakes or rivers, but the biomass here is much, much higher.”

And this biomass can be turned into fuel. According to Biology Professor Michael Twiss, wastewater ponds would have to be re-engineered, but significant changes are not required.

“Right now,” he says, “these lagoons are designed to treat water, but subtle modifications could also generate the production of biofuel — such as biodiesel. And this means that we may have found a new, local source of energy.”

Wastewater systems are common everywhere. While each lagoon may hold only a limited amount of biofuel, there are many lagoons.

“Cities and towns are looking for inexpensive ways to generate electricity and they would prefer a green, renewable option,” says Twiss. “These pools could be that resource. Streetlights, traffic signals, these things could be powered by wastewater treatment ponds.”

The ponds have a unique characteristic, uncovered by Kring in the course of her research.

“It’s the fish,” she says, “or the lack of them. In natural lakes, there are more fish and they eat the zooplankton, making these organisms less plentiful and certainly less concentrated. However, in wastewater lagoons, predation is less of an issue. This is why we are seeing so much biomass here, and that makes it easier to harvest.”

Kring found another aspect to these lagoons that increase their potential as sources of energy: The zooplankton are, in a way, refining oil naturally.

“They’re eating the algae, which is the source of the oil,” she says. “They break apart the algae in their digestive tracts and they preferentially accumulate the oil in their structures and eggs. Due to their larger size, collecting zooplankton from water is much easier than collecting microscopic algae. So, harvesting zooplankton is less energy intensive than microscopic algae.”

Kring and Twiss recently published the results of this research in the journal Environmental Technology.