By Thomas Renner
The movement toward using renewable energy is just beginning to evolve in many United States communities. According to a report in Fortune in 2018, 18 percent of all electricity in the United States was produced by renewable sources in 2017, an increase of three percent from the previous year. The share of renewable energy consumption doubled in the United States since 2008, according to the report.
The city of Grand Rapids, Michigan, has been far ahead of most other communities in the commitment to green. The city was named “America’s Greenest City” by Fast Company magazine, and has received worldwide recognition for its efforts. The city’s initiatives include the world’s first Community Sustainability Partnership – which was formed in 2005 – and it includes more than 270 local partners across various sectors working together to advance sustainability in Grand Rapids.
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,’’ Baker said in a report on Groundworkcenter.org. “It is also an expectation from the workforce; our own employees insist on recycling.”
As part of its green initiative, the city is investing $57 million in a biodigester that will convert food waste to energy. The goal is to develop 100 percent renewable energy to power city buildings by 2025. Construction on the biodigester began in 2018, and it is expected to be operational by November. The city expects gas produced by the project will generate 60 percent of electricity needs for the city’s wastewater plant. “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.”
How biodigesters work
Anaerobic digesters produce biogas, which is mostly made of methane and carbon dioxide plus small amounts of other gases. Biogas contains about 55-75 percent methane and 24-44 percent carbon dioxide.
The anaerobic digester is a large, air-tight container or tank that does not contain any oxygen. The tank is filled with organic material, such as wasted or spoiled food, plant clippings, animal manure, meat trimmings and sewage after it has been treated. The bacteria, which can only live in places where there is no air, break down organic, biodegradable material over time and converts it to biogas and an inorganic fertilizer.
The Grand Rapids system revolves around three tanks with a capacity of 1.4 million gallons. Two tanks will be used for municipal biosolids. The other tank is an anaerobic membrane bioreactor that will quickly reduce organic waste.
Concentrated food waste from city businesses will be carried through a 10-inch transmission pipe that was installed by the city in 2018. The next phase of the project is the building of the biodigester, which is expected to be fully operational next year. People who live in Grand Rapids can pay a surcharge to use the pipeline as well.
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 phosphorous recovery once the biodigester is fully operational could eventually add an additional revenue stream for the city. The project is being funded with tax-exempt municipal bonds.
Biodigesters are uncommon in the United States. 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. High capital costs and risk to investors are primary reasons why biodigesters are not more common.
Building the system
Tetra Tech, a California firm, designed the project and The Christman Company, based in Lansing, Mich., is serving as the project’s general contractor. When construction began in March 2018, Nicholson Construction and Menard Group USA – the companies developing the groundwork where the biodigester will be located – discovered some early challenges.
Nicholson started preparing the foundations for the biodigester, but almost immediately encountered unforeseen obstacles. “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.
Workers also found onsite contamination from waste at a nearby railyard 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.”
The system requires pumps and mechanical equipment to power the digester, and workers need access to that equipment 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.
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.
“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, who led the company’s team along with project manager Andy Brown. “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.”
One of the key participants in Grand Rapids’ biodigester is Founders Brewing, which has been in business since 1997. The brewery recently embarked on an aggressive expansion plan, and expects to produce 900,000 barrels per year when the project is complete.
Founders was ranked second in the nation by American Homebrewers Association’s Top Breweries of 2018. But the Grand Rapids “King of Beers” has a lot of company. The city’s “Ale Trail” boasts more than 80 breweries, and was awarded the title of “Best Beer Town” by USA Today. The city also has a rich brewing history. The first brewery in Michigan, City Brewery, opened its doors in 1836.
Beer brewing, however, strains water resources. Craft brewers produce an average of three gallons of wastewater for each gallon of beer produce. For large breweries, the average is seven gallons of wastewater per gallon of beer. With the expansion plans of Founders, the company looked at options to handle wastewater, but that would have required investing in more equipment and dedicating space to handling waste. It worked out a solution with the city to become one of the first contributors to the biodigester.
“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, Founder’s chief production officer.
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 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. Clearly, the city takes its commitment to renewable energy seriously. The biodigester is one of its most notable examples.
“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.”
Thomas Renner writes on construction, manufacturing and other trade topics for United States trade publications. He can be reached at firstname.lastname@example.org.