Nashville’s Landfill Problem Might Have Unlikely Solution: Bacteria

---

At the current rate, the US is set to run out of landfill space in 17 years, but in the mounds of garbage, food waste exists that could be recaptured for soil and energy.

The Middle Point landfill in Nashville is the state’s largest with a daily haul of 4,000 tons of trash from 33 counties.

With it set to close in five or six years, city leaders felt pressure to find solutions for reducing the amount of waste it landfills. They turned to an interdisciplinary team at UT for help.

CEE Professor Qiang He has teamed with colleagues from UT’s Department of Agricultural and Resource Economics, Department of Biosystems Engineering and Soil Science, and Department of Economics, the College of Law, and the Howard H. Baker Jr. Center for Public Policy on the project.

Together, they are working on a plan to recapture commercial and institutional food waste from the landfill.

By using certain microbes in a dry anaerobic digester, they will be able to convert carbon from food waste into methane for electricity, with leftover residue being used as a soil supplement for farmers and anywhere that needs a rich soil amendment.

For the time being, the team is using a pilot-scale digester designed for processing brewery waste to conduct technical testing. Armed with a better understanding of the yield of methane or natural gas and an ability to fine-tune the optimal temperature to maintain the material, they will be able to apply their findings to a greater diversity of food waste.

He’s role is to optimize the process with regard to microbial populations. There are many variables to regulate between the feedstock, process condition, and the bacteria that’s involved.

He stressed that limiting the amount of water involved is critical because one of the advantages of dry anaerobic digestion is the production of a soil supplement with low moisture content that’s convenient to ship to locations in need.

Additionally, He said that if the methane that’s produced contains contaminants like hydrogen sulfide in the downstream processing, it can cause corrosion in pipes and equipment. To counter this, his focus will also be on reducing the microbes that produce corrosion.

“If we cannot prevent that from happening, then we have to design a process to scrub it out,” he said.

The team will also help set up economic parameters as they work to scale up the project for the city, with the pilot project on track to begin in March 2020.