More than 250 million tons of waste are generated annually in the U.S., but recycling and composting puts a bigger dent in that number each year. The city of Lebanon, Tenn., is doing its part with the upcoming construction of a waste-to-energy facility made possible in part by a $250,000 matching-funds grant awarded by the Tennessee Department of Environment and Conservation’s (DEC) Clean Tennessee Energy Grant Program.
Construction of the biomass gasification plant is scheduled to begin after the grant’s start date of Sept. 1, and once completed mid-2016 is expected to generate big savings for the city, said Kathy Glapa of the DEC Office of Sustainable Practices.
“Some of the reasons why it’s important is it helps eliminate disposal costs for the city, it reduces what the taxpayers have to pay,” Glapa said. “The implementation of the project will consolidate waste streams at the wastewater treatment plant, while adding substantial energy and environmental benefits by reducing nitrogen oxide, sulphur oxide and fly ash.”
The state estimates an additional $75,000 in electricity will be generated by the plant, and it will reduce the amount of diesel fuel used to transport the wood being burned by more than 100,000 gallons annually. The plant is expected to process 27 tons of “woody biomass” per day and vendor PHG Energy estimates that as much as 64 tons of “wood waste, sewer sludge and used tires” can be consumed daily.
“Over the lifetime of the project, which is estimated to be 25 years, the entity is expected to save roughly $6 million,” Glapa said of the new plant, which is to be installed at Lebanon’s Hartman Drive Wastewater Treatment Plant. “This particular project I think is going to be the model for future cities and counties to deal with waste that can be used for energy sources rather than filling the landfills up.”
The city became interested in the idea, Glapa said, when they saw the results being achieved at a similar plant in Covington, Tenn., another PHG Energy project.
Lebanon Mayor Philip Craighead said the project validates a policy commitment to clean energy, and with federal funding accounting for 70 percent of the interest cost of their bond issuance, the program is fiscally responsible too. The city will use $5.5 million of the Qualified Energy Conservation Bonds initiative, a low-cost financing tool offered by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy that amounts to $3.2 billion nationally.
The energy generated by the plant is clean, Glapa said, because no harmful byproducts are created. The plant's only byproduct, she said, is biochar, also known as charcoal, which can be used as a soil additive or mixed with compost, adding even more value for the city.
Lebanon is the 13th commercial gasification plant installed by PHG Energy, whose website explains that a process called downdraft gasification does not incinerate wood fuel, but uses a “sequential, co-current flow, gravity-assisted, thermo-chemical phase change reactor” to generate fuel. More information about the company’s technology, along with a more detailed look at the Lebanon project can be found on the PHG Energy website.