Electrifying Opportunities from Beer Waste

MnDRIVE investigators are developing distributed wastewater treatments that transform carbon waste into clean electricity

Microbreweries are on the rise in Minnesota — as is the wastewater they produce. While many have come to appreciate the rich diversity these venues offer, most remain unaware of the waste per pint produced. Researchers at the BioTechnology Institute (BTI), however, are designing new strategies for purifying and transforming on-site waste into on-site electricity.

“Food-based industries are responsible for a lot of the carbon load discharged to our Metropolitan wastewater treatment plant,” says Paige Novak, an environmental microbiologist, engineer, and BTI faculty member in the Department of Civil, Environmental, and Geo-Engineering. As currently treated, this carbon-rich wastewater results in a huge energy demand when it reaches the treatment plant.

Local food-based industries like dairy, sugar beet, and beer routinely produce large quantities of carbon-rich waste water. According to the Brewers Association, brewing one pint generates seven pints of wastewater on average. While some larger craft brewers can cut that figure down to only a couple of pints, others (typically microbreweries) sometimes produce as much as 15-20 pints of waste per pint of beer.

“The bacteria I study chew up the carbon in brewery wastewater to generate electrons. Then they push these electrons past their outer surface and onto a metal surface,” says Kane. “That movement of electrons is the energy-driving force in cells.”

Kane is developing tech that harnesses this movement of electrons to generate power. Instead of inserting bioreactor cassettes into waste tanks, Kane envisions a system in which the pipes that carry wastewater are lined with a carbon cloth material that accepts electrons. Bacteria could then form biofilms along this material and eat carbon out of the water as it flows through the pipes — and in the process, generate electricity. This system might reduce the need for large waste tanks, allowing carbon-cleaned water to flow directly down the drain.

Kane gets her wastewater samples from Fair State Brewing Cooperative in Northeast Minneapolis, where Caleb Levar, a doctoral graduate of the Bond Lab, is the resident microbiologist on staff. “Right now, dumping wastewater down the drain is the easiest way for brewers to get rid of it,” says Levar. “Instead of putting yeast slurry down the drain, small breweries can sometimes ‘sidestream’ their waste by removing yeast slurry from the tank, killing it with steam, and feeding it to cattle.”

Yet sidestreaming is not always feasible or scalable. “If we could instead use that carbon to feed a bioreactor, there is an opportunity to significantly improve the waste treatment process,” says Levar. “But it does require some foresight in how to integrate these systems appropriately. It has to be something that’s easy for us to do as brewers.”

As they progress through the design process, Novak and Kane remain acutely aware of the practical need for their systems to be both cheap and easy to install. “If we want to put something out there that’s going to be useful, we have to make sure we know what people actually want,” says Novak, noting that most brewers are not as concerned about recovering energy as they are about reducing fees paid for wastewater treatment.

Furthermore, both researchers describe a need for collaborative efforts to address the fundamental problem of keeping waterways pure and clean. “Whatever tech gets us closer to solving a problem, the better it is,” says Novak, noting that a hybrid system fusing elements from her system with Kane’s (or others’) might end up producing the best results. “We are excited to take this amazing science from the lab and bring it to the real world to solve an important problem,” adds Kane.

“We have this wonderfully unique and abundant water resource in Minnesota,” says Levar. “We also have this wonderful resource at the University of Minnesota. These two resources should work together, the one protecting the other, to the betterment of industry in Minnesota.”

Currently, there are no cheap and easy ways to treat carbon waste on-site. Therefore, most businesses simply adjust the pH and dump it down the drain. Downstream at treatment facilities, however, the massive resources committed to purifying wastewater churn out greenhouse gas emissions. In response, the largest contributing industries are annually slapped with charges for waste treatment.

The good news is that Minnesota regulators are investing in promising new techniques to address these problems. In addition to an infusion of MnDRIVE research funding at the University of Minnesota, the Metropolitan Council of Environmental Services (MCES) has initiated a first-of-its-kind program of financial incentives for industries to clean up their own waste and keep it from ever reaching centralized treatment facilities. This idea of distributed wastewater treatment is catching on, but there’s a lot of work to do before researchers have hammered out how such systems could be practically implemented.

Novak’s idea is to develop bioreactors that enable finely-tuned microbial populations to eat excess carbon directly out of wastewater. As it turns out, the high concentration of carbon in beer wastewater is ideal for the specialized microbes she studies. In her research, she uses wastewater samples directly from Fulton Brewery in Downtown Minneapolis to develop and test new tech.

“Some of the microbes I study produce hydrogen as a byproduct,” says Novak. “Their other products can be eaten by different microbes that make methane from it.” The resulting gaseous combo could be used as a clean, combustible fuel to produce electricity on-site — but there must also be an efficient way of collecting the gas.

Novak is therefore collaborating with environmental and mechanical engineers to develop a hollow, sheet-like material. Microbes are encapsulated in the wet outside layer of this material and emit gas into its dry, hollow center. The gas can be siphoned out and used to turn motors that generate electricity. Novak envisions that sheets of this material could be folded into cassettes and inserted into existing waste tankage on site — first at breweries, and eventually in other industrial settings.

Aunica Kane, a post-doctoral BTI researcher working with Daniel Bond and Jeffrey Gralnick, BTI faculty members in the Department of Microbiology & Immunology, approaches the same problem of using microbes to clean wastewater, albeit with a different strategy. Kane studies bacterial populations that respire onto metallic surfaces. That is, rather than using oxygen to breathe, these bacteria breathe insoluble metals.

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