Clean Energy from Beer Waste?

MnDRIVE-funded researcher harvests natural gas from brewery wastewater

By Nick Minor

From industry pioneers like St. Paul’s Summit Brewery to small-town brewpubs, Minnesota’s craft beer industry has become a point of pride for local beer enthusiasts. But for every pint that flows through the tap, 3 to 10 pints of wastewater–high in carbohydrates, acids, and alcohol–end up in the municipal waste stream to be treated by the city. Breweries pay a premium to remove and treat this wastewater. Still, that same nutrient-rich content provides an ideal food source for hungry microbes capable of turning the waste into energy at the brewery.

With funding from the University of Minnesota MnDRIVE Environment Initiative, researchers led by Professor Paige Novak set out to treat this brewery wastewater while achieving two additional benefits: reducing the load on municipal water treatment systems and producing energy to help fuel brewery operations. 

Kuang Zhu, a recent PhD graduate from Novak’s lab, designed a 2-stage process to treat the brewery wastewater. In the first stage, microbes (called acetogens) feed on the wastewater. Housed in an airtight, oxygen-free compartment, they digest the carbohydrates in the wastewater, producing hydrogen and acetate as byproducts. These byproducts are then siphoned into a second oxygen-free compartment where microbes (called methanogens) consume the acetate, and produce methane, a significant component of natural gas. One of the team’s original innovations was to house the microbes in beads made of a carbohydrate derived from brown algae. This keeps the active microbes in the reactors where they can do their work simply and with little energy expenditure. Hydrogen collected from the first stage, and methane collected from the second can be used to generate power for the brewery while the treated water, significantly cleaner, flows to the local municipal wastewater treatment facility.

Scaling up this research from the lab to the brewery, presented its own set of challenges. Partnering with Fulton Brewing in Minneapolis, the team embarked on “months and months of troubleshooting,” Novak recalls. There were constant tweaks, leaks, and spills; parts to replace, cross-contamination, and even a small wastewater “explosion,” all within a wastewater storage room that averaged a steamy 85 degrees Fahrenheit. 

But this process, slow and tedious though it may be, is a critical part of science. Novak credits the demonstration grant from MnDRIVE, a state-funded initiative that aims to connect basic research with real-world impacts, for making this possible. “It’s such a different kind of trial and error and troubleshooting process,” explains Novak, “and there are so few funding sources for that kind of work. Going through this demonstration project has been invaluable because we figured out all those things we need to pay attention to when we do this again.” 

“Plus,” Novak adds, “it’s been really fun.”

One part of that fun is a public art exhibit that was stimulated by a requirement of MnDRIVE grants to have a public outreach component. After meeting local artist Aaron Dysart at a conference, Novak knew his data-driven approach to art would be a perfect fit for her project and for making the required outreach component much more visible. Dysart plans to create a disco ball suspended outside the Fulton taproom. Not just any disco ball, Dysart’s installation will spin at a rate proportional to the gas produced by the bioreactors. It will project color sequences linked to the ratio of hydrogen and methane. Mounted sideways, Dysart’s disco ball project will be a stream of data bubbling up from the wall of the brewery’s outdoor beer garden.

Of course, getting the bioreactor design into the real world won’t just involve science and engineering. It also requires understanding how the bioreactor fits into the marketplace. Again, thanks to MnDRIVE funding, Novak was able to partner with the Carlson School of Business to conduct some preliminary market research. “They analyzed the technology and the market,” Novak says, “and evaluated different food and beverage industries that would be a good match for our technology.” To Novak’s surprise, Carlson’s research showed that breweries weren’t the only market for the bioreactor. “Breweries don’t typically spend enough money [for this to make a big difference for them].” Instead, potato chip makers and candy manufacturers, both of which generate high concentration wastewaters, could benefit more from the team’s design. Furthermore, the business school team clearly showed that before the technology will be accepted by industries, the design must be plug and play and ready to work out of the box, regardless of the nature of the waste stream.

This goal is now much closer to reality thanks to progress made through the demonstration grant. One day, Novak hopes high concentration industrial wastewater treatment will be as simple as “getting your beads, dumping them in, and watching them go to work no matter what.” MnDRIVE funding not only helped move the technology forward, it also allowed the team to identify industries most likely to benefit from the research and provided an opportunity for consumers to learn about wastewater treatment through a public art installation.            

Nick Minor is an alumnus of the Science Communications Lab, pursuing a master’s degree in zoology and physiology at the University of Wyoming. He can be reached at minor092@umn.edu.