The Ohio State University’s Blackwell Inn Diverts Food Scraps to an Anaerobic Digester Where It Creates Methane Gas for Electricity and Vehicle Fuel

Quick Process

Today, the Blackwell Inn strategically places 10-gallon Rubbermaid totes with lids around the hotel and in the back of the house. “Food waste from our dish areas, prep areas, some of our service-station areas and kitchenettes in our conference rooms fills the totes,” Pratt explains. “All post-consumer food waste, any leftovers from buffets, coffee grinds, all our biodegradable unbleached paper towels—they don’t really add any benefit but it keeps them from the landfill—also go in the totes.”

The Blackwell Inn grinds food waste from dishwashing, prep and servicestation areas, as well as kitchenettes in conference rooms, through the Grind2Energy machine from InSinkErator. PHOTO: Grind2Energy

The Blackwell Inn grinds food waste from dishwashing, prep and service-station areas, as well as kitchenettes in conference rooms, through the Grind2Energy machine from InSinkErator. PHOTO: Grind2Energy

Members of Pratt’s stewarding staff, mostly students, collect the totes and place them 12 to a cart and roll them to the trash dock. Stewards dump the totes onto a 4-foot stainless-steel table where they sort and remove objects not meant for the grinder, like silverware. “If you have a lot of pastry or dry goods, they need to be mixed with something else,” Pratt says. “Because there are a variety of totes on the cart, the stewards can mix the food.”

Pratt compares the machine to a giant garbage disposal with a large hole on top. “There aren’t any blades,” she says. “It contains very fine teeth and mostly works from centrifugal force that sucks the waste through the very small teeth.”

David Krems, director of sales and business development for Grind2Energy, adds one of the key differences between the Grind2Energy system and a commercial or residential disposal is the amount of water necessary to create and pump food slurry. “At home, you turn on the disposer and you run water,” he says. “However, to optimize the energy value for quasar’s anaerobic digesters, you don’t want extra water in the tank where the slurry is stored.”

The grinder’s speed ensured Pratt didn’t have to hire a point person specifically to oversee its operation. “It turned out the stewards could just work it into their day,” she says. “With the newest system, it only takes 10 to 15 minutes to run through a dozen totes. It’s actually very simple.”

Cost comparisonsThe food-waste slurry is stored in a sealed tank where it is held for about two weeks before a vacuum truck sucks out the slurry and hauls it to the anaerobic digester in Columbus. The storage tank not only prevents odors and subsequent pests, it also ensures the food slurry maintains its energy for the anaerobic digester.

“Our food waste is actually powering about 900 homes in Ohio,” Pratt says. “Some of it also is made into what they call dual fuel, which is part methane and part regular gas. They’re working on converting the city fleet to dual fuel because it burns cleaner; it’s much more energy efficient; and, of course, it comes from byproducts of food.”

Cost Savings

The Blackwell Inn’s initial investment was only to buy collection totes, which InSinkErator now includes in its Grind2Energy program. InSinkErator offers the Grind2Energy system for a monthly fee, similar to how manufacturers of commercial dishwashers and coffeemakers lease and service their machines. “The technology is costly, plus the installs can be complex so we don’t ask the customer to pay for anything upfront,” Krems explains. “We maintain and monitor the equipment, so if any repairs are needed it’s on our dime. We also monitor the tank remotely; when it’s nearly full, we send a truck to suck it out and take it to the digestion facility. To simplify the process for our customer, all fees for hauling and disposal at the digestion facility are part of our monthly fee.”

About the Author

Christina A. Koch
Christina A. Koch is editorial director and associate publisher of retrofit.

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