Photo courtesy of City of San Diego

Photo courtesy of City of San Diego

The City of San Diego, Calif., has taken a major step toward switching its entire fleet of refuse and recycling collection trucks from diesel fuel to compressed natural gas (CNG).

Last month, the city completed the second phase of construction on a new CNG fueling station at the Environmental Services Department facility. There are now 13 operational time-fill fueling posts that can each fill up to four CNG vehicles simultaneously. The city currently has 20 CNG vehicles operating in its fleet.

Once fully built out, the station will allow the city to replace its existing fleet of 131 diesel-powered collection vehicles with CNG vehicles by 2022 and reduce the amount of diesel fuel consumed by more than one million gallons annually.

“By transitioning to compressed natural gas, we’re making our fleet greener and saving money at the same time. This is a win-win for San Diegans and will help us reach our climate action goals,” said Mayor Kevin Faulconer.

Based on current fuel prices, city officials expect the project will save the city between $1 million and $1.5 million annually in fuel costs once the entire fleet is fully converted. Estimates show that by constructing the facility and compressing the needed fuel for the vehicles, the City of San Diego will be paying less than $1 per diesel gallon equivalent of natural gas compared to the average of $2.39 per diesel gallon.

Operators fuel the vehicles at the end of their workday and leave them to fill overnight. The entire fleet is fueled simultaneously using a series of large compressors that take pipeline gas from 35 psi (pounds per square inch) to 3,600 psi. Natural gas is stored on the trucks at this “compressed” state and then reduced to 110 psi when it is injected into the engine. CNG is utilized in combustion engines similar to gasoline, which means that the new vehicles will be much quieter compared to the city’s current diesel trucks.

There are two remaining phases to complete the fueling station. Once complete, the facility will have the ability to fill up to 140 vehicles simultaneously. It also has a "quick fill" dispenser that will draw off storage to fuel a limited number of trucks that are unable to get fuel during the normal 8 p.m. to 5 a.m. time fill fueling window. 

The total $5.3 million fueling station project is funded partially by a $250,000 grant from the California Energy Commission and $2 million from the city’s Recycling Enterprise Fund. The remaining costs will be covered by the general fund. Additionally, San Diego Gas and Electric, the natural gas supplier, spent $1.2 million to increase the pipeline size to accomodate the increased volume of natural gas needed for this fueling station.