SANDPOINT — A recently-installed generator at the waste treatment facility is saving the city a tidy sum on utility bills — and it didn’t cost a dime.
A new machine installed at the treatment plant in August is using methane produced during the system’s process as a means to generate power. A combined heat and power generator, the new addition stands to save the city an estimated $40,000 a year in electrical costs, said City Planner Jeremy Grimm. The purchase and installation of the machine was funded through American Recovery and Reinvestment Act dollars distributed to the Idaho Department of Energy.
“We looked at several different options, and this gave us the biggest return for lowest upfront cost,” Grimm said.
When Grimm and other city staff learned that they had been awarded the grant to use for efficiency projects, they began investigating the money’s possible uses. They checked out approaches like solar panels and other measures before investigating the possibility of installing a woody biomass generator as for energy creation. The approach seemed promising until staff discovered it posed an issue for environmental regulations.
“As we got further into it, we learned that to meet air quality standards, we would need to add a very expensive precipitator,” Grimm said.
With the woody biomass project nixed, city staff reoriented the project toward methane power generation. The region’s waste water treatment system uses digesters in which microorganisms break down biodegradable material. These digesters require precise heating to function properly.
“They work a lot like human stomachs,” Grimm said. “When the bacteria in there processes waste, it produces methane as a byproduct.”
The methane was previously treated as a waste product with no practical benefits. However, in an odd reversal, staff members are now researching ways to increase the level of methane produced by the system. They used some of the grant money to build a titration system that provides a range of benefits. For one thing, it allows companies like Litehouse and Laughing Dog Brewery to dump their high-strength waste, which they previously paid to have removed, at local locations. That saves both them and the city money, because staff can then measure the waste out in spurts to produce a great deal more methane. And more methane means more savings.
“We’re still trying to find that perfect recipe for producing methane,” Grimm said.
Between study costs and the actual machinery purchases and installation, the entire project cost about $250,000, a sum covered by the federal grant. If savings estimations prove accurate, the machine should cover those costs in a matter of years.
“We may explore the opportunity to build another CHP generator a few years down the road,” Grimm said.