Carmel streets department reports 27% per-mile CO2 drop after switching some trucks to B20 biodiesel

At the April 22 Climate Action Advisory Committee meeting, Ryan Mert, project manager for the Street Department, told members the department has purchased six new diesel trucks and moved several medium-duty vehicles back to B20 biodiesel after a prior, short-lived conversion to gasoline. He said the department’s recent sample showed a 27% reduction in CO2 emissions per mile and a roughly 37% improvement in fuel economy compared with the gasoline vehicles they replaced.

Mert said the department’s biodiesel vehicles returned fuel economy in the “17–18” miles-per-gallon range versus about “10–11” mpg for the gasoline models they replaced, and that a large sign truck now averages about “7.3” mpg compared with “5 to 5.5” mpg on the gas engine it replaced. “We got a 27% reduction in c o 2, emissions per mile driven on our biodiesel trucks compared to the gasoline engines that we had, and then, obviously, 37% increase in fuel economy,” Mert said.

The department described the biodiesel as B20 (20% biodiesel, 80% petroleum diesel). Mert said smaller vehicles are generally compatible with B20 conversions; some larger diesel vehicles require changes to their emission-regeneration hardware and sensors, and those changes can be costly. “A lot of those don’t have the ability because there’s, the … sensor, which does the regen on, our large trucks would have to be replaced because they can get clogged with biodiesel,” he said, adding the retrofit cost for some large vehicles is about $10,000 per vehicle.

Committee members asked about alternatives such as full electric, plug-in hybrid and natural gas. Mert said full-electric trucks available today often cannot accommodate plows or other street-equipment mounts; battery packs are integrated into the frame and complicate plow mounting. He said hybrids or smaller electric vehicles (the department purchased four Ford Mavericks for non‑plow uses) are part of the mix for staff who do not need a 250/550 truck daily. The department has also tested propane and a hydrogen fuel-cell vehicle but reported limited success with those technologies so far.

On the scale of the analysis, Mert said his short comparison used 14 days of vehicle data for the recent sample and that the two-week offset equaled “200 or 300 pounds of CO2 just from those 6 trucks” compared with the gasoline baseline. He recommended using the EPA’s conversion tools and the fleet’s telematics to roll up longer periods and to estimate annual avoided emissions and associated public‑health benefits.

Separately, Mert noted operational benefits from storm cleanup: most of the tree and storm debris hauled during recent cleanups went to Tiffany’s and Midstate with discounted dump fees, and much of that material will be chipped into mulch instead of going to a landfill. He told the committee the first days of the cleanup generated about 60 tandem loads of material and that staff planned to compile a full total after the event.

Members asked for follow-up data rollups (seasonal comparisons and annualized estimates), per-vehicle replacement planning and a clearer cost comparison (fuel dollars saved versus any incremental biodiesel price). Mert agreed to provide more detailed rollups for committee review.

“We can utilize that data and multiple websites,” Mert said of longer-term calculation options; “one of the easiest is the EPA’s website. It will convert that carbon that we've not just reduced, but avoided.”

The committee did not take a formal action on the presentation; the discussion ended with members encouraging the department to present a longer sampling period and cost/benefit numbers to the group at a future meeting.