SPUR’s report Critical Cooling recommends 42 options for reducing local carbon emissions. This is one of them. To learn about all 42 ideas, read the full report

Convert the City vehicle fleet to biodiesel fuel

Urbanist Article
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Municipal Transportation Agency


  • The price of a gallon of biodiesel exceeds the price of petroleum diesel by $1.25
  • The carbon content of biodiesel fuel is about 15.7 percent lower than petroleum diesel


Switching the City fleet to biodiesel would have a minimal impact on San Francisco’s emissions, and is not particularly cost-effective at over $100 per ton of carbon reduced. This is largely because biodiesel is only slightly less polluting than regular petroleum diesel.

What we do now
San Francisco’s 2004 Climate Action Plan found that the City’s own fleet of vehicles emitted approximately 81,045 tons of CO2 emissions in 1990, or approximately 1 percent of all emissions citywide and 3 percent of all transportation emissions. This figure does not include Muni or other transit vehicles.

What we could do
Biodiesel fuels have a lower carbon content than standard diesel, reducing CO2 emissions. Blends of 20 percent biodiesel with 80 percent petroleum diesel, known as B20, can be used in standard diesel engines. In May 2006, Mayor Gavin Newsom signed an executive order requiring all City departments using vehicles that consume diesel fuel to switch to 20 percent biodiesel, or B20. The City has since met this target, a milestone that was noted in the city’s 2008 environment plan.1

Under a three-year contract awarded in 2006, the City’s regular fuel supplier will supply it with biodiesel. It is not known how much the biodiesel requirement increased the City’s costs in the award of this contract. If we assume that the price of a gallon of biodiesel exceeds the cost of a gallon of petroleum diesel by $1.25, then the program would have cost the City about $129,000 per year. The cost per ton of emissions abatement would be about $100.

Carbon savings potential
We estimate that San Francisco’s municipal fleet uses approximately 750,000 gallons of fuel per year. Using a methodology developed by the Center for Clean Air Policy2, and assuming a fleet-wide fuel economy of 25 miles per gallon, we estimate that the new policy replaced 150,000 gallons of petroleum diesel per day with 155,119 gallons of biodiesel. Given the lower carbon content of biodiesel, this change would decrease CO2 emissions by about 1,200 metric tons per year.

1 “SFFoward, Building a Bright Future, Environment Plan 2008.” www.sfgov.org/site/uploadedfiles/mayor/SForwardFinal.pdf
2 CCAP Guidebook Emissions Calculator. http:\\www.ccap.org/guidebook