Pierce Transit (a transportation agency based in the state of Washington) recently received approval from the Environmental Protection Agency to fuel its bus fleet with renewable natural gas (RNG). The approval means that about 143 of Pierce Transit’s 155 buses are now running on RNG, produced from biogases at a nearby landfill.

The Western Washington Clean Cities Coalition cites Pierce Transit as the first transit agency in the nation to adopt RNG fuel for public transportation purposes.

What Is Renewable Natural Gas?

According to the American Gas Association, renewable natural gas is gas “derived from biomass that is treated and upgraded to pipeline quality natural gas.” There are a variety of biomass sources that are used to produce renewable natural gas, including agricultural residues, animal manure, energy crops, waste from landfills or wastewater treatment plants, and woody biomass.

Using RNG as a fuel source can be beneficial from both an environmental and economic standpoint.

Environmental Benefits of RNG

Scott DeWees, project manager at Washington State Clean Cities, commented on one of the central environmental benefits of using RNG: low carbon emissions.

“Renewable natural gas is among the most climate-friendly fuels on the market today,” said DeWees. “By using this locally-produced, waste-derived fuel, Pierce Transit will reduce the carbon emissions of its fleet by 80 percent—while also investing in our regional economy.”

As DeWees mentions, renewable natural gas does have low-carbon properties. But according to the American Gas Association, RNG also offers another significant environmental benefit: fewer greenhouse gas emissions.
It works like this: methane, which would normally be released directly into the atmosphere, is instead captured for conversion into renewable natural gas. The captured methane is then combusted, resulting in the release of a much less harmful greenhouse gas.

In fact, the American Gas Association states that when renewable gas is used as a transportation fuel, it produces more than 25 percent less greenhouse gas emissions than gasoline.

Pierce Transit Headquarters The headquarters for Pierce Transit in Lakewood, WA. 92% of Pierce Transit’s bus fleet are now running on RNG. The remaining buses in the fleet are diesel-hybrid electrics. Credit: Pierce Transit.

Economic Benefits of RNG

Using RNG as a fuel type can also save money. According to Carol Mitchell, a spokesperson for Pierce Transit, the agency spends about $.70 per gallon equivalent on average for RNG. Compared to the national average for gasoline, at $3.55 per gallon,* RNG saves Pierce Transit over two dollars a gallon.

“While the financial benefits of using natural gas for fuel are significant, and the rebates for RNG are an added bonus,” concluded CEO Lynne Griffith. “It is just one more way that Pierce Transit demonstrates its commitment to the environment and continues its long history of pioneering sustainable, environmentally-friendly operations.”

*Numbers for August 2013, from Consumers Report at http://www.consumerreports.org/cro/2012/11/average-gas-prices/index.htm

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