A Michigan county sees success with a bioreactor project that helps pumpers and provides energy for the community.
Eight years ago, Smiths Creek Landfill in St. Clair County, Michigan, was searching for a source for its bioreactor landfill project. At the same time, area pumpers were looking for alternative places to dispose their septic waste — especially in winter when land spreading is not allowed. The landfill’s Research, Development and Demonstration Project, which takes in septic waste to feed its bioreactor, solved both problems.
“It’s been a win-win situation for both us at the landfill and for the pumpers,” says landfill manager Matthew Williams. “We’re getting rid of waste and creating energy. We get something to fuel our bioreactor and the pumpers get a cost-effective, easy way to dispose of their septic waste.”
As pumpers across the country face more restrictions regarding land spreading, interest is rising in what Smiths Creek Landfill is doing.
The county worked with consultant CTI and Associates Inc. to develop the project, which was the country’s first septage bioreactor landfill. Using septic waste in the bioreactor speeds up decomposition in the landfill and helps stabilize waste faster. The landfill gas is captured and then used as a power source.
“The septic waste decays faster and creates more airspace, which will lengthen the landfill’s life span,” Williams says. “We can also capture more gas that we can use for renewable energy.”
CTI estimates the bioreactor produces nearly 40 percent of the methane gas for the landfill, which is about 60 miles north of Detroit. That gas powers two electric generators that produce up to 3.2 megawatts of electricity, which is enough to power 1,900 homes.
The process begins when pumpers hook up and then swipe an ID card to keep track of who is visiting the landfill and how much they are discharging. The septage travels through a rock trap that removes heavy items and then into a Muffin Monster manufactured by JWC Environmental that removes trash and mixes up the load so it’s more consistent. From there, the waste travels through a pH meter and then into a JWC Honey Monster that screens out solids and separates the liquids.
Solids — which make up about 2 percent of the septic volume — are dumped into bags that are buried in the landfill. The liquid is discharged to two 4,100-gallon lift stations outfitted with Gorman-Rupp pumps, through a 2,500-foot force main into a 50,000-gallon bladder tank. From there, it goes into another 50,000-gallon bladder tank. The first one is used to settle suspended solids, which originally got caught in the lines, so a second one was added, Williams says. The second bladder tank is connected to the bioreactor where the liquid is gravity fed through perforated lines into 10-foot layers of garbage. Four-inch perforated pipes extract the biogas.
Williams says the first couple years of the project were a learning curve as landfill workers adapted to working with septic waste.
“We were a pilot project so everything was new,” he says. “That first year, we had some frozen lines, but we learned from it.”
The county has benefited financially from collecting the septic waste, through both the nominal fees collected from pumpers dropping off their waste and the ability to generate more methane gas to create electricity, Williams says.
For the pumpers involved, using the landfill service is a quick option since they can quickly unload their tanks. It also costs less than going to the wastewater treatment plant and is faster than land-applying, Williams says.
Right now, the landfill only takes in waste from septic tanks in St. Clair County.
“We have a pretty consistent list of haulers who come here,” he says. “We’ve never had a problem getting enough septic waste for our project.”
On average, the landfill takes in about 4,000 gallons of septic waste a day.
The landfill’s Research, Development and Demonstration Project has garnered a lot of attention.
“We’ve had visits from state regulators, the EPA and other landfill operators to see what we’re doing,” Williams says. “We’re in active talks with two landfills who are interested in doing what we do here.”