A New York City treatment plant is slowly increasing its appetite for food waste to be converted to biogas for delivery to the natural gas grid
Three years into a pilot program aimed at keeping food out of landfills, New York City is making slow but steady progress.
From 1.5 tons of food waste per day when the initiative began in 2013, the Newtown Creek Wastewater Treatment Plant now accepts some 20 tons per day, turning it into biogas and, ultimately, energy.
Within a few years, the plant plans to accept 250 tons per day, and it has potential for up to 500 tons, according to Pam Elardo, deputy commissioner of the Bureau of Wastewater Treatment in the city’s Department of Environmental Protection.
With 8.4 million people, New York City sends about 1.3 million tons of food waste to landfills every year. About 500,000 tons come from restaurants, which, while encouraged to reduce and recycle waste food, are not yet subject to the city’s food waste separation regulations. Those regulations do apply to:
- Food service establishments in hotels with 150 or more rooms
- Food vendors in arenas and stadiums that seat at least 15,000 people
- Food manufacturers with a floor area of at least 25,000 square feet
- Food wholesalers with a floor area of at least 20,000 square feet
Overall, the city sends over 3 million tons of waste to landfills every year and aims to divert 100 percent of the food waste by 2030. “There’s a lot of interest in DEP, the city, and the mayor’s office to increase our sustainability and strive for a zero carbon footprint, and this is an important component of trying to get to that,” says Elardo.
Newtown Creek is slowly increasing the amount of food waste it accepts. To prevent plant upsets, just three of the plant’s eight 145-foot-high egg-shaped anaerobic digesters are used in the three-year pilot project. The food waste is mixed with wastewater treatment solids.
Garbage haulers collect the food waste from establishments in Brooklyn and take it to a Waste Management transfer facility a few blocks from the plant. There, a proprietary process converts the waste into a slurry that is introduced to the digesters.
One impediment to progress is the presence of forks, plates and plastics in the food waste. “We’re working with the Department of Sanitation and Waste Management to come up with ways to increase the purity of the food waste, and they’ve been doing a lot of work closing that gap,” Elardo says. “It’s a bigger problem than I thought it would be.”
That’s why Newtown Creek started with a pilot project. “The city has people doing outreach to broaden the amount of food waste that is diverted from the solid waste stream,” Elardo says. “There are educators working with schools and cafeterias, and people interacting with the private sector and food processing plants. It’s changing the way of thinking for millions of people that will make this successful. It will take a lot of persistence and a change in culture for us as a society in how we view waste.”
Better gas usage
The largest of the city’s 14 wastewater treatment plants, the 310 mgd (average) Newtown Creek facility was built in the 1960s and added the egg-shaped digesters in 2010. The digesters generate about 1.8 million cubic feet of biogas per day, and 40 to 50 percent of it feeds the boilers that heat the digesters and plant buildings.
In those digesters processing food waste, gas production has increased about 23 percent, and that will increase as more food waste is added. At present, excess gas is flared.
“Ultimately, we take that gas and put it through a scrubbing system, and National Grid will introduce it into their pipeline,” says Elardo. National Grid delivers natural gas to Brooklyn, Queens and Staten Island. Within a couple of years, Newtown Creek could provide enough gas to heat 5,200 homes.
“We’re still figuring out the economics,” says Elardo. “Because it’s a pilot, we’re not charging a tipping fee. Ultimately, it would make sense to have a tipping fee less than the cost of taking it to a landfill. We need to find a balance between how much gas we use in our boilers and how much goes to National Grid.”
Elardo is cautiously optimistic about the food waste program’s long-term potential: “There is nothing negative happening and we’re taking it slowly.”