October 4, 2009
A new view of food scraps’ potential
There’s power on your plate
By Nancy Remsen, Free Press Staff Writer
Instead of thinking “yuck” when faced with shriveled brown apple cores, slimly spinach leaves and stinky chicken bones, Dan Hecht of Montpelier thinks “energy.”
“There is value to be derived from stuff we throw away,” he said.
In an age when finding alternative sources of energy is both a state and national priority, Hecht points to the potential in a squandered resource: food scraps.
For one thing, it’s plentiful, Hecht said: “Every city and town in America already possesses a major source of renewable energy, one that does not need to be mined, harvested, refined or transported long distances.”
Hecht is project coordinator for the Central Vermont Recovered Biomass Facility, a research project that’s assessing the feasibility of collecting food waste, mixing it with manure and letting it stew until it releases methane gas, which can be used to produce heat and power, plus environmentally safe byproducts.
“The food garbage is the big innovation here,” Hecht said of this waste-to-energy project, seeded by a $492,000 grant from the U.S. Department of Energy. “Nobody is doing post-consumer food waste.”
Once the research phase is completed in December, the food power project would move from the proof-on-paper phase to proof in practice.
The plan is to tap 14 tons a day of food scrap in the Central Vermont Solid Waste Management District, combine it with 10 tons a day of manure from area dairy farms, and feed it into a biodigester to be built on the campus of Vermont Technical College in Randolph. The methane produced would be used either to fuel the college’s heating plant or to generate electricity for the campus.
What’s left — likely a thick, dark liquid — would have several potential uses, such enriching soil on farmers’ fields.
Hecht said this project is intended to produce a roadmap that others in Vermont and across the country could follow to make better use of food scraps. Hecht tries to avoid calling food scraps “waste” because they have so much energy potential: 200 to 400 percent more energy per ton than manure.
Ponder the potential in greater Burlington, with its many eateries, educational institutions and a medical center, Hecht suggested. New data developed by consultants for the research project estimate 245 tons of food materials is produced weekly in Chittenden County.
First step: fetch the food
Start where the food scraps originate, such as the dining hall at Norwich University in Northfield.
Twice a week, a truck from Central Vermont Solid Waste Management District comes to Norwich and collects 22 totes full of food scraps, said Paul Bento, general manager of dining services at the university. Serving 716,000 meals a year, Norwich ends up with a lot of food scraps: 207 tons last year, Bento said.
The Central Vermont district began diverting food scraps from landfills in 2004, sending the material instead to two composting sites.
“We had identified organics in 2001 as a priority for diversion,” said Donna Barlow Casey, executive director of the waste district. It’s part of the district’s zero-waste commitment.
Because of the largely rural nature of the district, Barlow Casey said the food-scrap initiative has focused on commercial and institutional producers, not residential. That would remain the case even with the added demand of feeding a biodigester, she said.
To satisfy the end-users of the food scraps, the district had to provide contaminate-free material — no plastic wrap or foil, just food.
“We have one the cleanest food-scrap programs in the nation,” Barlow Casey said. “When we talk about contamination, it’s just the tiny stickers on fruit and vegetables. We work with every single business that comes on board. We train their kitchen staff. There is a feedback loop. If we see forks, plastic or paper, we reject that tote. It’s that feedback system that keeps the food clean.”
The totes aren’t small like the composting jars that homeowners may keep on their kitchen counters. They are 48-gallon rolling trash barrels with lids.
How smelly is that? Barlow Casey says putting sawdust in the bottom and layering more sawdust or coffee grounds with the food scraps buffers the odor.
“It does work,” confirmed Bento at Norwich.
Barlow Casey said there are more than enough sources of food scraps in Central Vermont to continue to provide material for the two composters and meet the 14-ton-a-day requirement of the new digester. New data estimate 98 tons of food scraps are produced weekly in the region. The district currently has 77 customers providing 18 tons of food scraps a week. In anticipation of having to ramp up collections, she said, the district just began recruiting new customers.
Collecting and delivering the food scraps is an expense that has to be balanced against the benefits of producing energy from it, Hecht said. In planning how to collect it, he said, “You have to do it with the shortest possible distance.”
Now the power part
There are many variables but fewer unknowns about the process that would transform rinds, bones and eggshells into power once they arrived at the biodigester, proposed for a site on the back portion of the Vermont Technical College campus, Hecht said.
Simply, he said, the food waste would go into a “blender” with some water and the manure to create the feedstock that would be put into an anaerobic digester. Some microbes would break down the organic materials into two byproducts: methane gas and a nutrient-rich liquid.
One of the questions yet to be answered is what regulations apply to this process, Hecht said.
“As of right now, we don’t have specific rules for digesters,” said David DiDomenico, environmental material engineer with the Department of Environmental Conservation. State regulators have been working on revisions to composting regulations, he said. “Our plan is to make it more of an organics rule. We’d like to put in a part for digesters.”
Other pending questions have to do with the best uses for the methane and the liquid effluent.
The methane, for example, could replace the oil that fuels the college’s central heating system and warms 15 buildings, said Frank Reed, a consultant working with Vermont Technical College on the project.
But what about in summer, when heat isn’t needed? Reed said the methane could be used to make electricity. Or maybe making electricity would be the best option year-round.
There also are options to weigh with the liquid effluent. It could be spread on fields, or perhaps used to grow algae in a process that would produce biofuels, Reed said.
Four consultants will provide models to help the college identify the options that best fit its energy goals and wallet. Hecht noted the reports from the consultants will provide others interested in food power with information about alternatives that might work under different conditions than those found at Vermont Technical College.
VTC will decide this winter whether to go ahead with planning and construction. Reed predicted that when the reports come in later this fall, “I think we will find it is feasible.”
What will Chittenden do?
The Chittenden Solid Waste District is pursuing its own research on how to divert more food and other organics from landfills. The district recently requested proposals from consultants for a comprehensive study.
“What is happening now is, we are about to head into the second era of modern solid-waste management,” said Tom Moreau, executive director of the Chittenden district. “This is the second wave of investment, and organics are going to be a big piece.”
Moreau said he is monitoring the development of the central Vermont project. He has no question about the feasibility of the biodigestion process.
“I’m confident it will work,” he said. “It will demonstrate to us in Vermont that once we collect it, we can handle it.”
For him, the challenge is food collection — whether from residents or commercial producers.
“People get lazy. They just want to throw things away,” Moreau said. “How do you collect the material in a cost-effective and energy-efficient way, and how do you get over the yuck factor?”
Contact Nancy Remsen at 651-4888 or nremsen@bfp.burlingtonfreepress.com.
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