GRAND RAPIDS, Mich. (WOOD) — Despite some false starts, the city of Grand Rapids’ biodigester is now up and running.

The $85 million project is designed to reduce the amount of solid waste the city sends to landfills from its wastewater treatment plant and turn that solid waste into usable commodities.

The biodigester at the Grand Rapids Water Resource Recovery Facility on Market Avenue SW. (Aug. 3, 2022)
The biodigester at the Grand Rapids Water Resource Recovery Facility on Market Avenue SW. (Aug. 3, 2022)

There’s all kinds of biology, physics and engineering that go into the biodigester, but the best way to describe how it works is from the gut.

“When we talked about the digester, we always go back to we’re running a stomach,” Mike Grenier, Grand Rapids’ director of environmental services, said.

It starts with the solids that are mixed in with the 40 million gallons of water that flow into the wastewater treatment plant along every day.

Biodigester machinery at the Grand Rapids Water Resource Recovery Facility. (Aug. 3, 2022)
Biodigester machinery at the Grand Rapids Water Resource Recovery Facility. (Aug. 3, 2022)

“The sludges, the things we take off the bottom of the tanks, that’s solids — poop, dead bacteria we used to clean the wastewater,” Grenier explained.

The solids are scraped up and pumped into one of three biodigesters tanks at the Grand Rapids Water Resource Recovery Facility on Market Avenue SW near I-196.

“We basically let the bacteria that normally exists there break down that material just like you would in your guts,” Grenier said.

Among other things, the recipe produces methane gas.

“We capture the gas. We go ahead and clean that up to the DTE pipeline standard specs, which means it just has to be methane, Grenier said. “This year, we’re budgeting about $2 and a half million in gas revenue.”

The process eliminates much of the waste produced by the traditional treatment methods. Phosphorus released in the process can be used as fertilizer. The heat generated is used to heat and power the operation. The amount of sludge removed from the plant and taken to a landfill has been reduced by up to 40%.

Biodigester machinery at the Grand Rapids Water Resource Recovery Facility. (Aug. 3, 2022)
Biodigester machinery at the Grand Rapids Water Resource Recovery Facility. (Aug. 3, 2022)

“We’ve been talking about sustainability for a number of years. This is one way we can carry out those values,” Grand Rapids Managing Director of Public Services James Hurt said.

What began five years ago as an estimated $35 million project ended up with a price tag of $85 million. Add-ons, like the system capturing natural gas, and cost increases, some fueled by supply chain shortages, added the additional $50 million. City leaders say it was either build the biodigester, which actually makes something out of the waste, or expand the plant’s traditional treatment capacity.

“If we were to expand the plant, it was about $130 million in today’s dollars,” Hurt said.

If the project works the way it’s supposed to, there is room for expansion.