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Turning Memphis Wastewater into Energy

TVA is capturing methane gas from the T.E. Maxson Wastewater Treatment Plant in Memphis and transporting it to the adjacent Allen Combined Cycle natural gas site where it will be used to help power a steam turbine and reliably generate five megawatts of energy—enough to power at least 3,000 homes.

FEBRUARY 10, 2017—Large, thick plastic sheets bubble up like creatures from the Black Lagoon. Underneath are not scary movie monsters, but rather methane, carbon dioxide, and other gasses rising up from a wastewater treatment plant.

Allen methane plant sheets

Soon, the gas inside those scary-looking bubbles will be used to make environmentally friendly energy at the Allen Combined Cycle Plant in Memphis.

Through a partnership with the City of Memphis, TVA is capturing methane gas from the T.E. Maxson Wastewater Treatment Plant adjacent to the Allen Combined Cycle natural gas site. The new infrastructure will clean, dry, and transport that methane gas to the Allen CC site. There it will be used in an auxiliary boiler to make steam that will be sent to the steam turbine to generate at least five megawatts of electricity, enough to power at least 3,000 homes.

“This project allows us to beneficially reuse methane, a greenhouse gas that would otherwise be incinerated, while at the same time helping the city of Memphis reduce their air emissions,” said Dan Tibbs, general manager of Major Projects in Generation Construction.

“We knew when we started the Allen project, biogas was one of several environmentally innovative initiatives we wanted to pursue.”

plant construction

The use of biogas in Memphis is not a new idea. The Allen Coal Plant has also burned biogas from the Maxson plant, but with only limited success due to moisture and other issues with the quality of the biogas, which created maintenance issues for the coal-burning equipment. These previous issues have driven the need for additional moisture removal and treatment systems at Maxson to improve the quality.

For this project, TVA is investing up to $20 million in infrastructure at both the Allen CC site and in upgrades to the city of Memphis equipment in order to reliably deliver the methane gas to the Allen CC site. From there, it will heat a turbine to generate power. Tibbs estimates at peak production rates, methane gas could account for six or even eight megawatts of the plant’s total power output.

The overall Allen CC project is helping to reduce Memphis’ air emissions. When the plant comes online in the summer of 2018, it will be the most efficient in TVA’s natural gas fleet. Work on the plant is more than 65 percent complete, with more than 700 employees and contractors currently onsite. One of their tasks is to connect the biogas into this area to be used as part of the generation process.

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