FOR IMMEDIATE RELEASEJan. 18, 2001
Contact: Kathryn Kopchik 570-577-3260 [email protected]
Bucknell/Vanderbilt Professors Hope to Reduce Landfill Waste
LEWISBURG, Pa. -- Millions of bacteria are busily converting food waste into methane gas and soil nutrients in a pilot project at the Lycoming County landfill to determine if a full-scale plant could cut by up to 70 percent the amount of organic waste now being buried.
The project is directed by Thomas D. DiStefano, associate professor of civil and environmental engineering at Bucknell, in collaboration with Richard E. Speece, centennial professor of civil and environmental engineering at Vanderbilt.
They have completed a year-long $99,500 feasibility study for the Lycoming County Resources Management Services Inc., which operates the landfill, to test an anaerobic (using no oxygen) process for biodegrading waste. Based on promising results, the county commissioners have extended their contract for two more years.
"The anaerobic process is a technology that could divert a substantial amount of waste from the landfill and extend the life of the landfill," DiStefano said. "I am not aware of anyone doing this complete process with an anaerobic system."
Based on test results, DiStefano hopes eventually to convert from 50 to 70 percent of the biodegradable waste that is now being landfilled into methane gas and soil nutrients, called soil amendments or conditioners that could be sold commercially. Organic waste contributes about 25 percent of the waste that comes into the landfill.
DiStefano has been researching anaerobic systems for several years. When county officials suggested that the process be tested at the landfill, he contacted Speece, an international expert on anaerobic biotechnology and his mentor as an undergraduate engineering student when both were at Drexel.
Speece called DiStefano's approach "a novel concept. This is cutting edge, and it is a privilege to be associated with something that probably 10 years down the line will be commonplace."
Some 1,000 tons of trash and garbage are brought daily to the landfill which rises to a 200-foot-high hill off U.S. Route 15. Some 5 million tons of waste, from a six-county area, have been buried on the site which first opened in 1978. At the present rate of dumping, the landfill will only last 11 more years, said Michael D. Hnatin, staff engineer for LCRMS.
In the first year of the project, the anaerobic process treated food waste from an area food processing plant. "Tests indicated that the process may be amenable to the entire waste stream after recyclables and construction and demolition materials have been removed," DiStefano said.
The project is part of a comprehensive Green Technology Initiatives program the county commissioners have initiated to find ways to bury less waste by recycling more and developing byproducts to sell. Building facilities for the entire program would be a multimillion-dollar project.
If successful, the complete county plan would cut by more than 70 percent the total amount of trash and garbage going into the landfill and could extend the site's life to mid-century, Hnatin said. The county has begun an aggressive recycling system to extract aluminum, plastic and other waste for reuse. Construction of a new $8 million recycling facility will begin in June at the 500-acre landfill complex.
Speece said, "Lycoming seems to be out front with this. As you look at public opinion, there's not much alternative. People will not allow anything to be done in their backyard. Where are they going to relocate? Social pressures have to be addressed. Imagine the unthinkable situation where there is no place to put your solid waste. It would be an untenable situation."
For the pilot project, three 10-foot high, 8 inches-in-diameter biological reactors were installed. The food processing waste is added to the reactors daily. One reactor, using recycled water, converts the garbage into simple organic acids which are then pumped to the second reactor where the bacteria convert the acid into methane gas. The residue left behind in the reactors is the relatively odorless compound that can be used as a soil nutrient.
The bacteria originally came from the Smucker's plant in Orville, Ohio, which uses them to degrade waste from jelly manufacturing. "We needed the bacteria as a seed for our reactors. Speece had worked with Smucker's before and contacted them," DiStefano said. Smucker's provided a couple of 55-gallon drums full of bacteria. The original bacteria now keep multiplying.
The methane gas can be used to produce electricity. The residue of soil nutrients can be used by such businesses as nurseries, golf courses and turf farms, Hnatin said. "When applied, the non-chemical nutrients are released slowly into the soil to improve the quality. We're very excited about this."
Using data from the preliminary work, DiStefano estimates that a full-scale anaerobic operation treating just food waste could produce up to 88 million cubic feet of methane per year and 2,600 tons of soil nutrient. Food waste accounts for about 10 percent of the entire waste stream. "So, if the reactors can ultimately handle 70 percent of the organic waste stream, the gas and soil amendment production would increase by a factor of seven."
Using bacteria to produce methane is nothing new at landfills. "Landfills are essentially biological reactors," DiStefano noted. The Lycoming landfill, which has a cogeneration plant on site, now sells PPL one megawatt of electricity daily that is generated by the captured methane (about 250,000 cubic feet per day). One megawatt is enough power to provide electricity to 1,000 homes, Hnatin said. However, considerable residue is left behind in the landfill.
Nor is biodegrading industrial waste with bacteria new. DiStefano said Milwaukee, using an aerobic process that requires oxygen, has been converting sewage sludge from waste water plants into compost and marketing it for 40 years.
The problem is the process needs oxygen to keep the bacteria alive and productive. Aerating the sludge consumes energy, whereas the anaerobic process produces energy. Perhaps more importantly, he said, adding oxygen produces gases that don't smell good.
"It is very, very difficult to contain odors from a large-scale aerated composting process," he said.
A drawback of the landfill-produced methane is that the gas is only about 50 percent methane; the remaining gas is carbon dioxide. DiStefano said it is not now economically feasible for natural gas companies to take all of the landfill gas because they would have to scrub out the carbon dioxide. About 80 percent of the current landfill methane is burned off in a flare with no recovery of the energy.
So far, the anaerobic process produces gas that is from 70 to 75 percent pure methane, which would make the gas more attractive commercially, DiStefano said.
Industries could retrofit their furnaces to use the methane at minimal costs, he said. Potential customers for the methane would include the federal prison at Allenwood, from whom Lycoming leases the land, and the nearby Great Streams Commons, a Union County industrial park.
The anaerobic process is contained in tanks, so the odor is minimal and not noxious. They'll work further to make the process odor-free. "It is extremely critical to make sure the process doesn't smell," Hnatin said.
The next step is to install additional biological reactors that will use different attachment mechanisms to biodegrade some of the municipal solid waste stream from homes and restaurants, in addition to the food processing waste.
The anaerobic biotechnology was first tested on industrial waste waters in the 1960s, but "got a black eye," DiStefano said. " It would work for a couple of months, and then fail, which led most to conclude that the anaerobic system is difficult to run and unreliable."
What people didn't know was the bacteria weren't getting the nutrients they needed, he said. The bacteria need a supplement of trace minerals that aren't contained in the food waste they're degrading, "much like humans taking a vitamin pill. On a weekly basis we add a cocktail that contains nickel, iron and cobalt at very low levels." If the bacteria don't get their cocktail, they don't biodegrade as efficiently, and sometimes not at all.
The next two years of the project will be critical in the decision to go ahead with the full-scale plant. "It has to be both technically feasible and economically feasible," DiStefano noted. "Our end is to assess the technical feasibility. Is this a technology we can apply reliably to biodegrade food waste and the municipal solid waste stream? After we've looked at that, engineers at Lycoming County will evaluate the economics."
If the anaerobic process does prove feasible, the county will build a facility that will house 14 reactors. They will be much larger than the current test reactors, measuring 6 feet in diameter, as compared to the pilot reactors that are 8 inches.
Besides the benefit of extending landfill life, the process could be an important source of energy. "If the Arabs imposed another oil embargo, the federal government would be pouring all kinds of money into developing something like this," Speece said.
DiStefano, Speece and Hnatin presented the project at the 16th International Conference on Solid Waste Technology and Management in Philadelphia in December.
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(Note 1: DiStefano can be reached at: phone 570-577-1647, [email protected]. Speece at 615-343-6328, [email protected]. Hnatin at [email protected], 570-547-2470)
(Note 2: Photos are available as e-mail attachments or prints. Contact Kathryn Kopchik, [email protected], 570-577-3260.)
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