By Paul Tower
Gundersen Lutheran has proved the old adage that “one person’s trash is another’s treasure.” In this case, City Brewing’s wastewater is Gundersen Lutheran Hospital’s heat and electricity.
Prior to working with Applied Filter Technology, City Brewing flared methane gas from its wastewater treatment process. With the proper equipment, City Brewing has been able to harness this gas and use it to help Gundersen Lutheran Health Systems achieve its goal of being 100 percent carbon neutral.
Most people don’t realize that the wastewater treatment process produces an impressive commodity that — when conditioned correctly — can provide a carbon-neutral energy source. Biogas, a naturally occurring byproduct of the anaerobic digestion process used by wastewater treatment facilities, is more than another waste to be disposed of. When harnessed properly, this power source can strengthen a plant’s bottom line and provide environmentally friendly power to on-site operations or nearby facilities.
Gundersen Lutheran and City Brewing’s recent venture demonstrates the potential value of mutually beneficial biogas partnerships. To deal with the complexities and nuances of the filtering and conditioning process, the partners contracted with Applied Filter Technology. AFT’s engineering analyses indicated that the waste stream was robust enough to allow Gundersen Lutheran to power a 633 kW generator, which in turn would provide 8 percent of the power for its La Crosse and Onalaska campuses in Wisconsin.
Gundersen Lutheran Health System, like medical facilities across the country, recently realized two important truths about the current business environment: Energy costs are spiraling out of control — GLHS spent $4 million on energy in 2007 — and customers and shareholders are increasingly demanding environmentally responsible and sustainable decisions from even the most unlikely organizations.
To address both issues, Gundersen Lutheran identified a group of green energy sources it could draw on and set a goal of being 100 percent energy neutral by 2014. As part of that energy mix, the company started working with City Brewing in 2009 to turn the brewery’s wastewater into a source of renewable energy for two of its hospitals.
As one of the largest beer makers in the United States, City Brewing was the perfect partner for Gundersen Lutheran because the beer-making process creates an enormous amount of wastewater — anywhere from three to 10 liters per liter of beer. The brewery produces almost 50 million cases of beer each year and has its own on-site wastewater treatment plant that processes 2 million gallons of wastewater daily. City Brewing recognized that converting its wastewater byproducts into a clean power source using anaerobic digestion and biogas power generation represented a significant financial opportunity.
Before entering into a partnership with Gundersen Lutheran, City Brewing needed to meet the first mandate that drives decision making at all wastewater treatment operations: produce clean, safe, disposable water from raw wastewater input. Wastewater treatment at a brewery is similar to many facilities’ multi-step treatment:
- First, the water runs through a process designed to remove coarse solids and large pollutants. Through flow equalization, screening, grit removal and gravity sedimentation, large waste like glass, bottle caps, labels, grit, grains and sand is removed.
- After solids are removed, the water is chemically treated with a pH adjustment and flocculation to remove toxic materials and colloidal impurities.
- Finally, the wastewater moves on to an anaerobic digester that removes the remaining contaminants, leaving as byproducts waste sludge and methane-rich biogas. The remaining water is clean enough to be released into local streams, rivers or sewers.
This process isn’t particularly new or exciting: Thousands of plants treat wastewater streams and produce clean water. But many of them squander an additional resource when they simply flare the methane byproduct into the atmosphere. With the appropriate equipment and treatment, this methane can be conditioned and upgraded to a variety of uses including electricity and heat generation, or purified to natural gas.
Brews to BTUs
City Brewing worked with a local company to install 633 kW Jenbacher generators, through which biogas would be routed then distributed on to the LaCrosse power grid. But City Brewing knew that the generators wouldn’t work for long unless the biogas was cleaned of the sort of contaminants breweries tend to create.
In brewery wastewater treatment, fluctuations in sulfur levels can be a concern. Although the corrosive effects of sulfur were well-known, there was as yet no proven, established process to effectively deal with the variability of sulfur contamination inherent in brewery wastewater treatment. The project team worked with Applied Filter Technology to implement a new sulfur-filtering process developed by British company DPS that uses SulfrStrip to clean and upgrade the biogas to meet the tolerances of the Jenbacher generators.
City Brewing’s gas cleaning skid, which helps turn two million gallons of wastewater into renewable energy every day.
First the biogas is washed, which dissolves the hydrogen sulfide in water. Next, the remaining gas reacts with iron during a state in which it cannot be converted to iron sulfide. Finally, hydrogen peroxide simultaneously oxidizes the sulfur and releases it from the iron.
Once the biogas was sulfur-free, it could be used to power generators to create electricity for nearby Gundersen Lutheran Hospital, with any excess distributed to the grid. The local utility then paid Gundersen Lutheran six cents per kW hour for the energy sent back to the grid. City Brewing benefitted because the waste heat from the generator and the engine exhaust was captured and used to power the digesters the brewery uses to treat its wastewater. Remaining liquid and solid wastes are converted into farm fertilizer, yielding another commodity byproduct from the wastewater treatment.
Challenges
Like most uncharted projects, this one was not without its challenges. It has taken more than a year to get the system up and fully operational. Though SulfrStrip provides excellent conditioning of biogas for sulfur, engineering errors by DPS in designing the system caused the project to run six months beyond the original timeline and the budget to double from $500,000 to $1 million.
After DPS abandoned the project, Applied Filter Technology, City Brewing and Gundersen Lutheran continued on. Applied Filter has absorbed nearly $500,000 in time and labor to re-engineer and install a new system that processes the sulfur effectively and generates consistent power. Even though the project is now operational and considered successful, the warranty continues: Applied Filter has given Gundersen Lutheran and City Brewing a 10-year gas-quality guarantee.
Conclusion
This project is expected to generate around 3 million kW hours of power a year. In addition to using biogas to power hospitals, Gundersen Lutheran incorporates wind power as a renewable energy source and another step toward its goal of 100 percent renewable power use. Gundersen Lutheran stands to make about $180,000 from the energy it sells back to the power company.
About the Author: Paul Tower, president and CEO of Applied Filter Technology, is a seasoned biogas professional with more than 30 years of experience in the field. During that time he has been an engineer, a salesperson, an advocate and an inventor. He holds a master’s degree in environmental engineering from the University of Wisconsin.
