Published on August 18th, 2014 | by Tina Casey0
NYC Has More Food Waste-To-Energy Tricks Up Its Sleeve
August 18th, 2014 by Tina Casey
If you’re hearing a loud buzzing right now, that would be the tubes heating up with news that New York City is set to expand its new food waste-to-energy pilot program this fall from a somewhat measly two tons per day straight on up to 50 tons per day. We’re still trying to track down the primary source for that stunning bit of news (send us a link in the comment thread if you got something), but in the meantime capitalnewyork.com has the lowdown.
The city is piggybacking the food waste to energy operation on to its existing Newtown Creek sewage (okay, so wastewater) treatment plant, so let’s take a closer look at that and see how the magic happens.
Food Waste-To-Energy At Sewage Treatment Plants
The key to the whole NYC food waste-to-energy program is a row of giant gleaming egg-shaped anaerobic digesters already on site at the Newtown Creek plant in Queens. The digesters are closed, carefully controlled environments in which microorganisms break down the organic materials in municipal wastewater.
The digestion process yields copious quantities of methane-rich gas, along with water. The leftover solids are relatively inert and can be used as a fertilizer or soil enhancer.
In past practice, treatment plant digester gas was typically flared off at the site. In recent years, however, it has become more common to reclaim digester gas to help offset energy use at the plant. Introducing digester gas to the natural gas pipeline grid is another emerging option.
Since municipal wastewater already includes some element of food waste, digesters at municipal treatment plants have been multipurposed for both food and human waste all along.
That’s particularly so of Newtown Creek. The largest of the city’s 14 treatment plants, it already handles wastewater from restaurants, schools, and other food scrap sources in addition to household sources.
The sticking point would be how much more food waste the Newtown Creek digesters can handle while still functioning efficiently. The current digester load is about 3,000 tons of municipal sludge, the thickish liquid left over from initial phases of the wastewater treatment process. City officials anticipate processing an additional 500 tons of organics (more on that below).
The NYC Food Waste-To-Energy Project
New York’s food waste-to-energy pilot project first crossed our radar late last year, when the city announced that it would partner with Waste Management and National Grid to collect organic waste, send it to the Newtown Creek plant, and process the resulting biogas into a usable product.
When the project was announced, city officials projected that the Newtown Creek facility had the potential to produce enough biogas to heat 5,200 city homes.
Waste Management had already begun collecting organic waste from schools and pre-processing it (basically, liquefying it in a really high tech way) for delivery to Newtown Creek by the summer of 2013. According to current information they’re doing about two tons daily.
Collecting large volumes of food scraps from businesses and institutional sites is one thing. The more complicated part involves organics collection for individual households. Under its household compost program, the city’s Sanitation Department began collecting food scraps from 30,000 single family homes and small multi-family buildings in parts of the Bronx, Brooklyn, and Queens last year. This year the program expanded to 100,000 households, reaching every borough except Manhattan.
Larger apartment buildings are also being recruited into the composting program. That group numbers about 50 so far.
Initial plans called for Waste Management to gradually build up to 5-10 tons if the pilot phase proves successful. The overall potential for the company’s Varick 1 Engineered Bioslurry facility is 250 tons per day, so the 50-ton expansion cited by reporter David Giambusso at capitalnewyork.com is just a way station toward the ultimate potential of 500 tons.
Food Waste Hearts Sewage Sludge
According to Giambusso’s account, all seems to be going swimmingly with the pilot project. The addition of food waste actually enhances the sludge in terms of energy content, and the resulting improvement could enable Newtown Creek to reclaim close to 100 percent of the gas produced by its digesters. Currently, about 60 percent is flared off.
With the higher-quality sludge in hand, New York also plans to get more sciencey over food waste-to-energy conversion and food/human waste co-digestion (yes, co-digestion is a thing), looking to produce leaner and more efficient processes.
If you’ve been following along with our livestock manure-to-biogas coverage with sister site Gas2.org, the city’s co-digestion R&D could also lead to cost-effective partnerships for combining livestock and municipal waste so stay tuned.