An ongoing effort to expand a waste-to-energy facility in Brunswick could eventually reduce the amount of sewage sludge and other refuse that needs to be buried in Maine landfills.
Last spring, a firm called Viridi Energy bought the anaerobic digester in Brunswick Landing, which for almost a decade has created energy out of organic waste, such as the solid material that’s removed from sewage at wastewater treatment plants.
Now Viridi is trying to scale up its production of electricity and natural gas at the biodigester, and it has partnered with a leading provider of waste services in Maine, Casella Waste Systems, to deliver sewage sludge as the fuel for that process. It will take more than a year to launch the expansion.
In addition to creating additional energy, the companies say that their partnership will help to stem the increased amounts of sewage sludge that have been sent to landfills in Maine in recent years — after it became clear that the sludge can be contaminated with PFAS chemicals and a 2022 law banned its use as fertilizer on fields.
Casella, which has a contract to run the state-owned Juniper Ridge Landfill, has been under some pressure to reduce the volume of sludge that it accepts there in recent years.
Last year, it successfully argued that more bulky construction and demolition debris would need to be buried at Juniper Ridge to stabilize the increased sludge deliveries, despite previous legislation meant to reduce the amount of that bulky waste coming to Maine from other states. But some officials and environmental organizations have questioned whether there are other ways to reduce the sludge deliveries and cut Maine’s dependence on other states’ construction debris.
Now, Casella says the bio-digestion process in Brunswick could reduce the volume of a sludge delivery by nearly 90 percent, for example shrinking 85,000 wet tons to 10,000.
There is growing urgency for Maine to reduce how much waste it sends to landfills, in part because two other facilities in Orrington and Hampden that are meant to turn trash into different forms of energy are in varying stages of closure or reopening.
However, Jeff Weld, a spokesperson for Casella, said the expanded Brunswick digester will not be able to remove PFAS contamination — also known as forever chemicals — in the sludge.
“I think where everybody would like to get to is a place where we’re implementing treatment technologies that take PFAS out of that waste, and then ultimately destroy those chemicals. I don’t think we’re there yet at this point in time from a technology standpoint,” Weld said.
Under the vision of the expanded digester, Casella will truck in waste from several wastewater treatment plants and give it to Viridi to treat. Microorganisms in the processor, when deprived of oxygen, will then eat the organic waste and produce methane. Viridi will then clean up the methane and use it in two ways: producing a renewable natural gas to heat homes, and fueling a generator to produce electricity.
In the process, the microorganisms will eat up the wet waste and leave behind the reduced volume of biomass that Casella will then take to a landfill.
The new system is set to be up and running by the first quarter of 2026, according to Bill Keller, the executive vice president of Viridi.
The Brunswick processor first opened under a different owner in 2015, providing 1 megawatt-hour of energy per hour, which is enough to meet the average electric needs of 1,000 homes.
The new plant, however, aims to provide additional electricity to the entirety of Brunswick Landing, which includes apartments, businesses and the Brunswick Executive Airport. It will also provide enough renewable natural gas to heat 3,600 Maine homes, according to Viridi.
That should cut energy costs for residents and businesses in the area, Keller said.
Brunswick’s city council recently approved a stricter zoning process for projects around the Landing, in part because of questions about how much more truck traffic, noise and odors could be created by the expanded digester and other projects.
But Keller said that, while the digester is operating, his goal is for it to be nearly invisible to the public.
“We don’t want anyone to be hearing us, we don’t want anyone to be smelling us,” Keller said.
Weld said the process will have the added environmental benefit of creating energy from a byproduct that would otherwise be going directly to landfills.
“If there’s value in the material, and you wouldn’t have to extract natural resources to create natural gas, and you don’t have to extract natural resources to create electricity, if it can come from your waste, you’re getting that much closer to a circular economy,” Weld said.
