Renewable Natural Gas from Landfill Fueling Local Buses

Aug 16, 2013

Natural gas from organic waste is gaining momentum as a renewable energy source, and a local transit agency is already on board. 

About 20 miles southeast of Seattle is King County’s last remaining landfill. Cedar Hills is 920 acres of rolling yellow grass growing on top of about five decades of people’s garbage. Little pipes speckle the hillsides, capturing methane as the trash decomposes.

Credit Bellamy Pailthorp

“Until we started processing the gas, all of it was flared at the north flare station. Simply burned off as waste," said Ron Earnest, plant manager of Bio Energy Washington.

The plant runs the natural landfill gas through rows of compression tanks and filters to make it pure enough to put right into a nearby pipeline. They call it renewable natural gas. Until now, this renewable natural gas had literally been going up in smoke. 

Ron Earnest

Some landfills burn this gas in generators to produce electricity. But Earnest says the return on the pipeline-grade natural gas they make here is five to seven times more profitable. Now, when Earnest sees what are piles of trash, he sees "dollar signs."

“The projection is that we’ll have usable landfill gas for the next 30 years for us to be able to process into natural gas, at this site," he said.  

The company buys the landfill gas from King County and sells its product to Puget Sound Energy. It also gets green energy credits from the federal government that can be traded for additional revenue.

A Huge Leap Forward for Local Transit

Credit Bellamy Pailthorp

A portion of Bio Energy Washington’s gas is powering a local transit agency.

Nearly all of Pierce Transit’s buses have a distinctive hump on top where natural gas tanks are located. They’re painted bright green with the agency’s motto, “The way to go!”

Pierce Transit converted its fleet from diesel to compressed natural gas in 1986. CEO Lynne Griffith says the move has saved millions of dollars a year and helped reduce the transit agency's environmental impact.

And now Pierce Transit has signed an agreement to run nearly all of its buses on renewable natural gas from the Cedar Hills landfill.   

“This seems the next natural step, is to look at ways of using resources that are right here in the community that for years have been going by the wayside, capture that as a larger commitment to the environment," Griffith said. 

It cost Pierce Transit only the time to fill out the paperwork. And the program generates a small rebate of about $1,000 a month based on the federal green energy credits generated at the landfill.

Ron Earnest, left, and Scott DeWees
Credit Bellamy Pailthorp

Scott DeWeese, who is working to reduce petroleum and diesel fuels for the Western Washington Clean Cities Coalition, believes Pierce is the first transit agency in the nation to use landfill gas for public transportation. He says it represents a huge leap forward, even for a fleet already running on natural gas.

“When you can use renewable natural gas, we are seeing a greenhouse gas reduction on the order of 80 percent. So this is a fuel that is kind of a best-in-class outcome for larger, heavier-duty vehicles,” he said. “It’s similar to using electricity generated from renewable resources. It’s that clean.”

DeWees says there are many other local sources of renewable natural gas that can be tapped such as sewage treatment plants, large dairies, and food waste. High costs upfront to build processing plants has stood in the way of financing some of these projects so far, but the hope is that Pierce Transit’s example will help pave the way for more production from these previously untapped resources.