MnDRIVE investigators are developing distributed wastewater treatments that transform carbon waste into clean electricity
by Colleen Smith
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 huge energy demands when it reaches the treatment plant.
Local food-based industries like dairy, sugar beet and beer routinely produce large quantities of carbon-rich wastewater. 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.
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.