The Role of Renewable Diesel
By: Chandu Visweswariah
Executive Summary
The dire, urgent and existential climate crisis we face is well-understood.
California has replaced nearly 65% of its diesel consumption with Renewable Diesel (RD). UPS has been transitioning a significant share of its fleet to RD. New York City uses RD for 12,000 municipal trucks. Westchester County airport and the Village of Tuckahoe are converting to RD. So, what exactly is RD? How much does it reduce emissions? When and where is RD recommended?
Here are the short answers:
Q: So, what exactly is RD?
A: RD is a drop-in replacement for diesel, but it is not a fossil fuel. It is made from sources such as vegetable oils, animal fats and waste oil by a process called hydrotreating. It is commercially available, albeit at a premium of $0.20 per gallon (the latest January 2025 data shows RD on par with regular diesel[1]). It can be freely blended with regular (petroleum) diesel in any proportion, up to 100%.
Q: How much does it reduce emissions?
A: When RD is burned, it produces Greenhouse Gases (GHGs) about as much as regular diesel does. However, because it comes from plant-based sources, credit is given for the CO2 absorbed when it was a plant in its past life. Taking into account lifecycle calculations, RD reduces GHG emissions by about 68% compared to fossil diesel.
Q: When and where is RD recommended?
A: We see RD as a stopgap fueling solution when a diesel vehicle simply cannot be replaced with an electric equivalent. In situations where a diesel vehicle is in good shape, has significant remaining useful life, or where the electric equivalent is not available or affordable, switching to RD will make a significant dent in emissions for the remaining (hopefully short) life of the diesel vehicle. However, we do not recommend purchasing new diesel vehicles. And since there is no analog of RD for gasoline, we recommend that gasoline vehicles (including snowplows and school buses) be replaced as soon as possible.
Read on to understand the rationale behind our recommendations.
Introduction to Renewable Diesel
RD is made from sources like vegetable oils (canola, distillers’ corn oil, cottonseed oil, palm oil, soybean oil), animal fats (poultry fat, tallow from beef, white grease from pork) and waste oils (yellow grease and used cooking oil). The process involves treating the oil at high pressure with hydrogen in the presence of a catalyst, called hydrotreating, followed by separation of the useful diesel, called fractionation. The resulting diesel meets all the requirements for diesel internal combustion engines and can be blended with regular diesel in any proportion.
Analysis of Emissions
The figure below summarizes emissions from driving a Class 8 semi-truck 1,000 miles.
The calculations supporting these numbers are included below in Appendix A. A few important notes:
- “Grid electricity” implies an electric truck charged in Westchester County, New York, using regular grid power.
- “2030 grid electricity” assumes that New York State meets its goal of 70% clean power in the grid by 2030 and again assumes charging in Westchester County.
- “NYPA power” means an electric truck of a public entity (school or municipal government) that has access to 80% clean power from New York Power Authority.
Recommendations
Today, for public facilities, shifting from diesel to NYPA power will reduce emissions 87.9%, and shifting from RD to NYPA power will reduce emissions by 58.8%. These are both very worthwhile reductions in GHG emissions. Even in cases where NYPA power is not available, we recommend transitioning to electric trucks because emissions will automatically reduce as the grid is cleaned up, whereas a diesel purchase will lock in emissions for 10 to 12 years.
Based on the above calculations, our recommendations and talking points are shown below.
- The climate crisis is a dire and urgent existential threat, requiring us to decarbonize all aspects of society as rapidly as humanly possible.
- Gasoline vehicles like snowplows, gas buses and police cars should be electrified as soon as possible, resulting in a significant reduction in Greenhouse Gases (GHGs). There is no equivalent of RD for gasoline. In particular, municipal governments and school districts should never buy another gasoline vehicle. This will require capital investments in EVs and chargers, to be weighed against monthly savings in maintenance and fuel costs.
- Diesel vehicles should be electrified as soon as possible, again resulting in a reduction of GHGs. Municipal governments and schools should never buy another diesel vehicle.
- If there is an existing diesel vehicle, and replacing it with an electric equivalent is not possible for whatever reason at this time, it should be fueled for the rest of its (hopefully short) life with RD to achieve GHG reduction. This can be done easily and without additional capital expense, but at a slightly higher price per gallon. This represents low-hanging fruit that should be harvested at once.
Appendix A: Emissions Calculations
This Appendix compares Greenhouse Gas (GHG) emissions of diesel, renewable diesel and electric class 8 trucks.
Diesel GHG Emissions for Driving 1,000 Miles
Average fuel efficiency of a class 8 diesel semi-truck = 5.7 miles per gallon[2]
Number of gallons of diesel required to drive 1,000 miles = 1,000 / 5.7 = 175.44
Note that mining, refining and transporting fossil fuels causes a 30% fossil fuel overhead[3]
Effective number of gallons required to drive 1,000 miles = 175.44 * 1.3 = 228.1
GHG emissions = 228.1 gallons x 22.38 pounds of CO2e/gallon / 2204.62 pounds per ton
= 2.32 metric tons
Electric GHG Emissions from Grid Power for Driving 1,000 Miles
Average electricity needed to drive a class 8 semi-truck 1 mile = less than 2 kWh[4]
To be conservative, 25% average uplift due to cold weather during 3 months of the year
= ( 2 * 9 + 2.5 * 3 ) / 12 = 2.125 kWh
Electricity needed to drive 1,000 miles = 2,125 kWh = 2.125 MWh
Electricity overhead due to transmission/distribution losses = 4.2%[5]
Effective electricity needed to drive 1,000 miles = 2.125 * 1.042 = 2.21 MWh
eGRID 2022 carbon intensity of electricity in Westchester (NYCW) = 976.1 lbs CO2e/MWh5
Total emissions = 2.21 MWh x 976.1 lbs CO2e per MWh / 2204.62 pounds per ton
= 0.98 metric ton
An important point: as New York cleans up its grid power towards its Climate Leadership and Community Protection Act (CLCPA) goals, this number will reduce year-over-year.
Electric GHG Emissions (Grid Power After 2030) for Driving 1,000 Miles
The CLCPA has a goal of 70% clean energy by 2030[6], up from 30% now8. Another way of saying this is that grid power will be 30% dirty vs. 70% dirty now. Hence, assuming that CLCPA goals are met, the emissions from driving 1,000 miles = 0.98 * 30 / 70 = 0.42 metric tons.
Electric GHG Emissions from NYPA Power for Driving 1,000 Miles
Most public facilities in New York get their power from NYPA, which is more than 80% clean[7], whereas general grid energy in New York is 30% clean[8]. Another way of saying this is that NYPA power is 20% dirty, while grid power is 70% dirty. Hence, the emissions from driving 1,000 miles = 0.98 metric tons * 20 / 70 = 0.28 metric tons.
Renewable Diesel (RD) GHG Emissions for Driving 1,000 Miles
RD has a carbon intensity of 30 g CO2e per MJ, compared to 102 g CO2e per MJ for low-sulfur petroleum diesel[9] (or ~90 to 100 g CO2e per MJ for regular diesel[10]). Hence, the lowest possible emissions from driving 1,000 miles with RD = 2.32 * 30 / 102 = 0.68 metric tons.
[1] https://afdc.energy.gov/fuels/prices.html
[2] https://afdc.energy.gov/data
[3] https://medium.com/enrique-dans/fossil-fuels-dirty-to-use-dirty-to-transport-352ad18f440c and https://illuminem.com/illuminemvoices/energy-to-waste-fossil-fuels-dirty-secret
[4] https://www.tesla.com/semi
[5] https://www.epa.gov/system/files/documents/2025-01/egrid2023_summary_tables_rev1.xlsx
[6] https://www.nyserda.ny.gov/Impact-Renewable-Energy
[7] https://www.nypa.gov/about/the-new-york-power-authority
[8] https://www.inspirecleanenergy.com/blog/sustainable-living/new-york-renewable-energy
