Renewable Revolution: A Michigan City Looks to Leave Fossil Fuels Behind

Grand Rapids water and wastewater utility projects provide a big boost toward the city’s goal of 100 percent renewable energy.

Renewable Revolution: A Michigan City Looks to Leave Fossil Fuels Behind

An artist’s rendering shows the Grand Rapids biodigestion facility, which is under construction. The three digesters are the cylinders in the foreground.

When the city of Grand Rapids, Michigan, committed to achieve 100 percent renewable energy by 2025, Mike Lunn knew the water utility would need to make big plans for conservation and energy production.

As in most cities, drinking water production and wastewater treatment in this Michigan city are the biggest electricity users. Lunn, utilities director, estimates that those two account for about half the city’s power consumption.

Providing all that power from renewable sources will be a big chore, but the utilities are used to big projects. In 2015 for example, the city completed, four years ahead of schedule, a nearly $400 million project to separate its storm and sanitary sewers. The resulting reduction in wastewater volume translated to nearly 30 percent lower power consumption for treatment.

The Grand Rapids Water System covers about 137 square miles and serves some 280,000 people. Although the city is on the Grand River, it draws water from Lake Michigan, 38 miles west. The 110 mgd (design) Lake Michigan Filtration Plant pumps about 40 mgd on average. The Water Resource Recovery Facility (61.1 mgd design, 40 mgd average) is operated by the Environmental Services Department and serves Grand Rapids and 11 other municipalities.

Reducing the load

Grand Rapids had no renewable power sources in 2005 when the city first set renewable power goals. It hit the 20 percent milestone in 2007 and reached 34 percent by early 2019. That means the goal of 100 percent renewables by 2025 is still a long way off. The next step, already under construction, is a $57 million biodigestion project that will provide 50 to 60 percent of the Water Resource Recovery Facility’s power.

Three digesters will produce biogas for a turbine-based combined power and heat system connected to the utility power grid. Turbine heat will be captured to keep the digesters at the optimal temperature. Electricity beyond the recovery facility’s demand (3.5 MW summer and 2 MW winter) will be available for sale to the utility.

Two of the digesters will be for wastewater treatment biosolids. The third, an anaerobic membrane biological nutrient removal system, will process food waste from sources such as Amway, Coca-Cola and Founders Brewing Co. “We brought in a concentrated waste line for the variety of wastes we would normally surcharge,” Lunn says. “That will reduce the loading we bring to the front of the plant.”

The solids from that digester will be transferred to the other two digesters, while the liquid will go back to the plant headworks. Eventually all the solids will go to dewatering and then to a landfill. Ground was broken for the project in December 2017.

Present and future

Grand Rapids already had some experience with renewable power. Solar power is in operation, and the city is evaluating whether and where to install additional solar. A 125-kW solar array is on the roof of the Water and Environmental Services Department building and another 500-kW array, in the planning stages, could help the Water Resource Recovery Facility shave its peak power loads.

In addition, Grand Rapids is evaluating solar power at the filtration plant. City officials hope a solar array there could power normal operations except during the peak summer months.

Geothermal resources are also in operation. The administration building at the Water Resource Recovery Facility uses heat from the effluent stream to heat the building. In addition, renewable natural gas is in the mix. Lunn expects the three new digesters to produce an excess of biogas that can be scrubbed and fed to the natural gas utility system.

Role for conservation

Water utilities usually can’t generate all the power they need to be 100 percent renewable without reducing consumption. “We have numerous projects to conserve electricity,” Lunn says. “The water system is evaluating all their pumps and motors. They just did some improvements to the pumps that move water from Lake Michigan to town. We put variable-frequency drives on the low-lift pumps that greatly reduce their costs.”

One way Grand Rapids has invested in renewable energy is through Green Generation, a program from Consumers Energy that allows customers to purchase renewable energy generated in Michigan. “We’ve been buying green energy blocks for a number of years,” Lunn says. “If we want to, we can buy renewable energy credits. They are very inexpensive.”

With the combined power and heat project under construction and renewable natural gas on the horizon, Lunn is confident Grand Rapids will reach its goal: “I’m 100 percent sure we’ll get there. I’m not 100 percent sure as to the process. It will be a combination of strategies. We’re going to reduce consumption, do some energy-efficient things and put in some solar. We’ll probably buy some renewable energy credits to offset the balance.”



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