Converting sewer grease to diesel
Waste product to fuel city trucks
DANBURY — The frying pan fat that gets washed down the drain can come back to haunt your sewer system.
Just ask England, where sewers have been beset with fatbergs — airlinersize sewer clogs of solidified grease and toilet matter that take jackhammer crews weeks to break up.
But can the same sewer grease can be converted into brown gold to fuel city firetrucks and heat public schools?
Keep an eye on Danbury, which will become the first city in Connecticut to harvest grease from the waste stream to produce biodiesel and heating fuel — up to 250,000 gallons in the first year.
That’s enough diesel to power Danbury’s entire truck fleet for a year, and leave the public works department 90,000 gallons leftover to sell.
“How great is it that we can eliminate the disaster of processing brown grease, capture it, turn it into a biodiesel and generate a revenue stream from it?” said Antonio Iadarola, Danbury’s director of public works and its acting city engineer. “This could be the next standard operating procedure for sewage treatment plants not only in Connecticut but the United States, and we could be the model for it.”
The pioneering plan, patented by a UConn professor and piloted in 2018 in New Haven, is part of Danbury’s $100 million wastewater treatment plant upgrade, expected to begin in the spring.
The innovative scheme would solve the expensive problem of waste grease disposal once it reaches the sewer plant, while saving Danbury at least an additional $300,000 in diesel and heating fuel costs each year, among other financial benefits.
The project’s potential impact reaches beyond the Hat City, however, said Richard Parnas, a professor in UConn’s Department of Chemical and Biomolecular Engineering, whose patented reactor mixes refined brown grease with methanol to produce the biodiesel.
“The larger story is that for every single wastewater treatment plant in the United States, fats, oils and grease are disgusting waste products that you have to pay to get rid of,” Parnas said. “If we are successful in Danbury (sewer grease) could become a commodity that has value, whereas today, that is not the case.”
Believing in grease
Supporters of Danbury’s $5.5 million greasetodiesel plan say the timing couldn’t be better.
As more residents and commercial kitchens comply with recent government mandates to keep grease out of the trash and waste stream, there is more of the disgusting stuff showing up at Danbury’s 8acre sewage plant on Newtown Road.
Danbury now handles 3,000 gallons of grease a day, which it mixes with woodchips and pays up to $80,000 annually to have carted away to a landfill or an incineration plant.
When the new 5,000squarefoot biodiesel plant is built, Danbury will be able to accept 500 percent
more grease daily, because the city will be converting it on site into truck fuel and heating oil.
Iadarola says the biodiesel plant could pay for itself in five years – or less if he secures government incentives available for biodiesel producers.
“We are looking at a payback period with incentives of 3.9 years, and after that, every buck that this thing makes goes into offsetting the costs of our (wastewater) plant and city expenditures,” Iadarola said. “This thing is a cash cow once we get it up and running and it’s paid for.”
The project’s supporters are confident because of a successful 2018 pilot program in New Haven when Parnas and his company, REA Resource Recovery Systems, produced 100,000 gallons of biodiesel from sewer grease.
If there is anything like the Danbury project in Connecticut, REA doesn’t know about it; nor does the Connecticut Conference of Municipalities, or the state Department of Energy and Environmental Protection.
DEEP referred questions to Parnas and his company.
Eric Metz, a partner in REA, said a similar greasetodiesel project that used different technology launched, but failed several years ago in San
Francisco.
That means all eyes will be on Danbury in 2020 to gauge the future of grease.
“If we can take this grease, which is impossible to deal with, and we can get a renewable energy source out of it, it’s a home run.” Iadarola said. “It’s why I am so excited about this project.”