Municipal wastewater flowing through local sewer lines could soon be converted into a reliable revenue generator and a source of clean energy under a new initiative currently moving through Nashville’s local government.
The Metro Nashville Council is weighing a set of municipal agreements between Metro Water Services and Burnham, an infrastructure development firm headquartered in Arlington, Virginia. Under the proposed arrangement, the company would build and operate a specialized renewable natural gas plant designed to capture treatment byproducts and turn them into marketable natural gas.
The planned facility is slated to process biogas generated at Metro Water Services' biosolids treatment plant, located at 1810 Cement Plant Road. Once transformed into high-grade renewable natural gas, the energy product would be injected directly into an adjacent commercial gas pipeline network for distribution.
While the initiative offers significant potential benefits, it still faces legislative hurdles before breaking ground. The ordinance authorizing the gas rights and associated property lease agreements passed its second council reading on September 15. The legislation must secure a final round of approval before the contract becomes binding, after which the project is expected to take up to two years to reach full operational status.
The private development partner, Burnham, focuses on collaborating with public utilities across the country to modernize wastewater infrastructure, lower operational overhead, and expand clean energy production. Under the contractual terms being considered, Burnham will take on the full responsibility to finance, engineer, build, own, and run the new processing facility.
In return for receiving a steady supply of biogas from Metro Water Services, Burnham will share a portion of the financial returns generated from gas sales and associated environmental commodities. Official fiscal notes submitted with the council agenda specify that the developer will pay Metro Nashville quarterly royalties amounting to 70 percent of the net revenue derived from the renewable gas produced on site.
The proposed agreement guarantees the city a baseline financial return, establishing a minimum annual royalty of $1 million per calendar year. This financial upside is bolstered by the sale of the gas itself as well as the monetization of renewable energy credits that accrue once the fuel enters commercial pipeline systems.
According to definitions established by the U.S. Environmental Protection Agency, these renewable energy credits are generated when one megawatt-hour of electricity is produced from a qualified renewable resource and supplied to the power grid. Such credits serve to distinguish green power from conventional fossil-fuel generation feeding the shared grid, enabling energy customers to purchase credits independently to match their clean consumption goals.
Under the specific timelines outlined in the gas rights agreement, Burnham would be required to begin construction within 18 months of the contract's effective date. The developer is then slated to achieve full commercial operations within six months of starting construction, retaining complete ownership of the specialized facilities it builds.
The accompanying property agreement involves leasing approximately 1.2 acres of municipal land situated at 1815 Cement Plant Road to Burnham. In exchange for site access to maintain and operate the conversion complex, the developer would pay Metro Water Services a nominal rent of $1 annually throughout the duration of the lease.
Both the gas rights contract and the ground lease carry a baseline term of 20 years. The legal framework also includes options for two separate five-year contract extensions, provided that both the municipality and Burnham mutually agree to the renewals.
The process of turning sewage byproducts into energy relies on distinct stages of wastewater management. Raw municipal wastewater enters municipal treatment plants laden with human waste, discarded food scraps, household oils, and various chemicals. During purification, treatment facilities separate liquid components from residual solid matter.
The isolated solids undergo specialized treatment to yield biosolids, which the EPA defines as nutrient-rich, semisolid sewage sludge that has been sufficiently processed to meet federal regulatory standards for use as agricultural fertilizers or soil conditioners. However, the secondary byproduct created during this stabilization process is what makes the energy project viable.
At Metro Water Services' biosolids facility in the Germantown area, anaerobic digestion generates an average of 1.5 million cubic feet of raw biogas every single day. This biochemical phenomenon occurs when specialized bacterial cultures break down organic matter in an environment completely devoid of oxygen.
Currently, the vast majority of this 1.5 million cubic feet of daily biogas is discarded through standard waste gas burners, resulting in routine flaring at the industrial site. Constructing the new dedicated processing plant would transform this operational baseline, enabling the beneficial reuse of 100 percent of the biogas generated at the biosolids facility.
Should the Metro Nashville Council grant its final approval in the upcoming legislative reading, the venture will move forward toward engineering and construction, pivoting the city from venting valuable industrial byproducts to generating millions of dollars in municipal revenue.
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