Something’s Brewing in Elaborate Michigan Project

Grand Rapids builds biodigester as part of renewable energy

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Much of the history of Grand Rapids, Mich., is borne in beer. Michigan’s first brewery, City Brewery, opened its doors in 1836 and German immigrants pouring into the city helped suds sales soar. Grand Rapids Brewing Company, brought on by the consolidation of six major local breweries, formed in 1893 and became the largest beer producer in West Michigan, producing 600,000 barrels annually.

The temperance movement in the early 20th century sparked a last call for the first breweries in the city, and for 46 years Michigan’s founding city for brewers did not have a single one. Canal Street Brewing Company, now called Founders, started the brewing comeback in 1997, and now, the city is regarded as a beer industry leader. USA Today awarded Grand Rapids the title of “Best Beer Town” and the city’s “Ale Trail” boasts more than 80 breweries. Founders was ranked among the top breweries in the U.S. last year by the American Homebrewers Association. Nearly every minute of every day, something is brewing in Grand Rapids.

Beer brewing, however, also puts serious strain on water resources. Craft brewers produce an average of three gallons of wastewater for each gallon of beer produced. For large breweries, the average is seven gallons of wastewater per gallon of beer. Founders, which sparked the brewery renaissance in Grand Rapids just 22 years ago, plans to produce 900,000 barrels per year when it completes an ongoing expansion project.

Founders is one of the key participants in a new project in Grand Rapids that will use wastewater to deliver renewable energy. The city is building a $57 million biodigester that will convert food waste to energy. Grand Rapids is committed to developing 100 percent renewable energy to power city buildings by 2025. “This coming together of the public and private sectors in the name of sustainability will have a positive impact on the future of our brewery and our city,” said Brad Stevenson, Founders chief production officer.

Work on the project started in February 2018, and some systems in the biodigester are expected to be operational in October or November 2019. The city expects gas produced by the project will generate 60 percent of the wastewater plant’s electricity needs. “We looked at future demand and other options,” said Mike Lunn, Grand Rapids’ utilities director. “But those options would have been more than $120 million. We calculated that this was going to be the best solution for future growth.”

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Strategy of the System
The system centers on three air-sealed tanks that will have a capacity of 1.4 million gallons. Organic waste will be combined with microorganisms to create the energy. Two tanks will be used for municipal biosolids, and the other tank is an anaerobic membrane bioreactor to quickly reduce other organic waste, such as that from the brewery and other Grand Rapids businesses feeding into the tanks.

The biodigesters will convert carbon to carbon dioxide and methane. The biogas produces energy—primarily electricity—that can be used to power and heat the buildings at the city’s Water Resource Recovery Facility.

Fats, oils, greases, and food waste create the most biogas when put into a digester. The tanks do not have any oxygen, and they must be maintained at an optimum temperature for anaerobic bacteria to digest the material. Many large biodigesters are kept at temperatures ranging between 86˚F and 100˚F. Bacteria working in the digester are sensitive to temperature, so cooler digesters require more time to break down biodegradable matter.

The city installed a 10-inch transmission pipe that will carry concentrated food waste from Founders and other businesses to the treatment plant. The waste will then be recycled through the biodigester to create the biogas. The pipeline was installed in June 2018. The next phase of the project, building the biodigester followed by start-up and testing, is expected to be completed in January 2019. Grand Rapids will also allow people who pay a surcharge to transport waste to the concentrated waste tank.

The project is being funded with tax-exempt municipal bonds. Electricity production from the biodigester is expected to offset the costs of the investment and will help keep consumer rates steady. The sale of city-generated phosphorus recovery once the biodigester is fully operational could eventually add an additional revenue stream for the city.

Grand Rapids has traveled down the biodigester route before. A biodigester was included in its first wastewater treatment plant in 1931. The system remained in place until the late 1970s, when increased industrial waste and inefficient performance resulted in the closure of the biodigester.

While some communities have invested in biodigesters, high capital costs and risk to investors have been primary reasons why they are not more common. According to the American Biogas Council, there are only 1,241 wastewater treatment plants in the United States using an aerobic digester, and fewer than 900 use the biogas they produce.

Building the Infrastructure
Earthwork, foundations, concrete, and masonry work started in March 2018. Electrical and mechanical work started in November, while the two-mile sanitary pipe that carries waste from Founder’s Brewery and other businesses to the Water Resource Recovery Facility opened in June.

Tetra Tech, a California firm, designed the project and The Christman Company, based in Lansing, Mich., is serving as the project’s general contractor. Nicholson Construction and Menard Group USA developed the groundwork where the biodigester will be located.

There have been construction challenges from the start. Nicholson needed 15 feet of fill across the site to support the structures. “The combination of unsuitable soil, fill, and the proposed structural loads required ground improvement to meet the settlement criteria,” the company said on its website.

Additionally, construction workers found onsite contamination from waste at a nearby rail yard when the project began.
“We had planned on some of that, but it was in excess of what we
had planned,” Lunn said. “That was one of the biggest challenges.”

Another potential challenge could emerge when the biodigester is fully operational. The neighboring city of Lowell closed a biodigester in February 2018 after less than three years in operation because of odor control issues. Decaying food waste created an odious stench that tormented residents for months. The biodigester nearly exploded, and thousands of gallons of waste spilled onto the ground.

Lunn said carbon filters and other technologies will be used to control odor in the Grand Rapids biodigester. A similar system has already proven effective in the city’s wastewater treatment plant to control odors from raw solid waste. “Any time you take on a big project you have concerns,” Lunn said. “I think we have this one designed with significant resources so that odor control will not be an issue. We’ve done a good job in the design phase and we’re confident we won’t have those concerns.”

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Safe Access to Equipment
Pumps and other mechanical equipment power the digester, and they require access for repair and inspection. Christman selected 19 products from The BILCO Company, including floor doors and roof hatches, that will allow workers access to equipment when the biodigester becomes operational. Architectural Building Products of Byron Center, Mich., provided the doors.

“BILCO provides a wide range of sizes that we need and could deliver to the project on time, including very large custom-built units,” said Eric Sawatzki, the assistant project manager for Christman. “A really appealing feature is the fall protection grating option for our standard-sized floor openings. This provides immediate protection from falls through the floor opening for construction personnel as well as users at the plant. It saves the expense of installing a rail system around every opening.”

The project includes eight 4’ x 4’ roof hatches with safety railings on the roof exterior. There are also 11 floor doors of various sizes, including some with drainage. Some doors were also customized for the application. The doors are made with stainless-steel hardware and corrosion-resistant materials. They also include engineered lift assistance for one-hand operation.

The safety grate provides a permanent means of fall protection. It includes a safety-yellow powder coat paint finish, and stainless-steel hardware for corrosion resistance. BILCO, which has been manufacturing specialty access products for more than 90 years, can install grates on doors prior to shipment. Retrofit kits are also available for field installation.

“Most of the products from BILCO are floor hatches that will allow them to be opened to lift pumps and equipment through the floor if service or replacement is needed,” said Sawatzki, who led the Christman team along with project manager Andy Brown. “Others are for access to the large concrete tanks to perform inspections. They are going to be an important part of maintenance and upkeep of the biodigester.”

Committed to Sustainability
Going green is not an accident in Grand Rapids. The city was ranked among the top five medium cities (population 101,000–350,000) by Expedia for its initiatives. “Between its Silver Line fleet of hybrid electric buses and the thousands of acres of parkland, Grand Rapids is eager to make the earth a better place,” Expedia said in a report.

In her first State of the City address in 2017, Mayor Rosa­lynn Bliss said environmental sustainability was one of her top priorities. One of her projects is the Mayor’s Greening Initiative, an environmental goal for a 40 percent tree canopy citywide. The city planted more than 2,000 trees in 2016 alone. The city was named “America’s Greenest City” by Fast Company, and the Water Environment Federation recognized Grand Rapids with a “Utility of the Future” award for its comprehensive plan in the recovery of resources, such as water, energy, and nutrients.

The Grand Rapids business community has also done its part to help the city’s commitment to sustainability. Rick Baker, president of the Grand Rapids Area Chamber of Commerce, said the entire community has shown commitment to environmental causes. “It is more of a conscious and intentional effort about what we should be doing and how we can contribute,” he said in a report on Groundworkcenter.org. “It is also an expectation from the workforce; our own employees insist on recycling and things like that.”

The biodigester is one more innovative step in the city’s commitment to sustainability and preserving the environment. Beer production, one of the city’s first major industries that helped Grand Rapids become the second largest city in Michigan, will play an important role in that effort.

“As energy recovery becomes more valuable, a lot of other communities will be looking at biodigesters,” Lunn said. “We’ve always been engaged in resource recovery. This is a project that could be a template for a lot of other communities.”

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