King County begins RNG production at water treatment plant

By King County, Washington | June 01, 2018

King County, Washington—which has converted methane to natural gas for more than 30 years—is now a leading producer of clean, renewable biofuel that can be used by commercial vehicles.

The purified renewable natural gas produced at King County’s South Treatment Plant in Renton can replace diesel fuel in commercial vehicles, capitalizing on a federal program designed to power more transportation with renewable energy. Renewable natural gas sales last year yielded more than $6 million in revenue for King County’s Wastewater Treatment Division.

“We are demonstrating to the rest of the country how local governments can work together to build a sustainable clean-energy economy,” said King County Executive Dow Constantine. “By producing renewable natural gas at our treatment plant, we are reducing greenhouse gas emissions and the region’s reliance on fossil fuels.”

King County has been purifying and selling renewable natural gas from its South Treatment Plant for longer than any other wastewater facility in the country. It is a direct substitute for the fossil-fuel derived natural gas that typically flows through local pipelines.

The environmental benefits of renewable natural gas are significant. Biogas is a byproduct of the wastewater treatment process, and is often burned off. By converting this waste gas to a transportation fuel, the emissions profile of both wastewater treatment and transportation is significantly lowered.

As a transportation fuel, renewable natural gas also generates far fewer air pollutants than diesel fuel. Each year, the volume of renewable natural gas produced at the South Treatment Plant is the energy equivalent of about 1.7 million gallons of diesel fuel.

Clean Energy, the leading provider of natural gas fuel and renewable natural gas fuel for transportation in North America, is currently delivering the renewable natural gas produced from South Plant to its Washington fueling station network.

The five stations fuel about 1.5 million gallons of renewable natural gas annually, sourced from this local production facility. One of the largest local end users is Recology, an employee-owned waste management company that uses the renewable natural gas for their garbage trucks that roam the region’s neighborhoods.

In addition to renewable natural gas production at South Treatment Plant, King County’s Cedar Hills Regional Landfill in Maple Valley is also a large producer of renewable natural gas. Collectively, King County’s efforts to convert waste products into resources resulted in more than $14 million of revenue from the sale of renewable natural gas and renewable electricity generated in 2017.