Longmont to fuel trash trucks with natural gas by the end of 2019

June 25, 2019. By the end of 2019, the City of Longmont, Colorado, expects to be fueling 11 new trash trucks with compressed natural gas (CNG) from the biogas that is currently flared at its wastewater treatment plant (WWTP) anaerobic digester. “The genesis of this project was simply trying to find a use for the biogas being created at our wastewater treatment plant,” explains John Gage, a civil engineer in Longmont’s Environmental Services Group, adding that currently, 75 percent is flared because only a portion is needed for heat at the WWTP.

   With 11 of its existing diesel trucks coming due for replacement, the city evaluated diesel versus renewable fuels. “We determined that renewable natural gas (RNG) was better than diesel,” says Gage. “The reason is two-fold. One, we have no control over the price of diesel, so cost is a component. And two, if you look at the carbon emissions from diesel compared to RNG, the difference is significant. Natural gas is lower than diesel, but RNG is lower still.”

Longmont estimates that the new facility should save the municipality approximately $400,000/year, between money not used to buy 90,000 gallons of diesel fuel and earning RIN credits through the U.S. Environmental Protection Agency’s Renewable Fuel Standard (RFS) program. The RINs (Renewable Identification Numbers) can be sold to obligated parties, which include petroleum refiners and importers of refined fuels to the U.S.

   The City received two grants for the RNG project — $1 million from the Colorado Department of Local Affairs for the biogas cleaning equipment, and $385,000 from the Regional Air Quality Council to cover all but $5,000 of the $40,000 cost differential for the CNG trash trucks. Replacing 90,000 gallons of diesel fuel with RNG will reduce greenhouse gas emissions by about 1,000 metric tons of carbon dioxide (CO2) equivalents annually.