Fueling Our Cars With Recycled Animal Fats

A safe and clean alternative to gasoline.

Gasoline: dangerous, toxic, and yet, essential. While gasoline-powered vehicles are an essential part of everyday life, they also contribute to air pollution. Most cars use an internal combustion engine that mixes gasoline with air in a combustion chamber. The car’s machinery then ignites and burns the gas (1). Anytime gasoline is burned, the combustion produces greenhouse gasses such as carbon monoxide and nitrogen oxides (1). A 2019 study conducted by the United States Environmental Protection Agency found that twenty-nine percent of greenhouse gas emissions can be attributed to transportation with vehicles such as cars, trucks, airplanes, and ships (3). The mere act of driving a car is causing global warming and putting our planet’s future into great jeopardy (l). 

The shift to electric vehicles is a step towards solving this problem. However, it cannot be relied on as the sole solution. Less than 1% of vehicles in the United States are electric because they are a relatively new invention. Not everyone is inclined to drive electric cars either, which means that Teslas are not going to stop global warming. We need another alternative to gasoline (4). 

Biodiesel, a mix of recycled cooking oil and animal fats, is a renewable alternative for gasoline that does not contaminate the air when used (5). Biodiesel is made through transesterification, which is the process of separating the glycerin––the natural compound from the vegetable oils––from the actual oil and fats. With the glycerin removed, the result of the transesterification is methyl esters, the chemical form of biodiesel (5).

 In 2004, Harvard University began using biofuels to power its shuttles, becoming the first Ivy League School to do so (6). Harvard’s shuttles use a substance of eighty-percent diesel and twenty-percent soybean oil, and the university built their own gas station for the mixture on campus (6). In 2016, James Stock, Harvard Kennedy school faculty member and first recipient of the Climate Change Solutions Fund grants, led a group of undergraduate students in testing their school’s transportation fueling method and its sustainability (9). Students came away from this class with a broader understanding of biodiesel and how it can be implemented in everyday life for cleaner energy. 

In 2018, more than seventy-eight percent of vehicles have been approved to use biodiesel as fuel instead of gasoline (7). There are over 60,000 jobs at 125 biodiesel production plants across the United States. The plants have the capacity to produce three billion gallons of biodiesel. The use of biodiesel reduces the cycle of greenhouse gasses by eighty-six percent, reduces the emissions of hydrocarbons or methane by sixty-seven percent and lessens particulate matter, such as smog, dust, and soot, by forty seven percent (7). 

Biodiesel is not perfect, however. The main downside to this alternative for gasoline is that it is not well-suited for cold temperatures and can “gel” which would require a heat tank to maintain (8). That being said, biodiesel is still a safer, cleaner, and economically beneficial  alternative to gasoline. 


  1. Gasoline and the environment – U.S. Energy Information Administration (EIA). (2018). Eia.gov. Retrieved from: https://www.eia.gov/energyexplained/gasoline/gasoline-and-the-environment.php#:~:text=Gasoline%20use%20contributes%20to%20air%20pollution&text=The%20vapors%20given%20off%20when,carbon%20dioxide%2C%20a%20greenhouse%20gas.
  2. Alternative Fuels Data Center: How Do Gasoline Cars Work? (2022). Energy.gov. Retrieved from: https://afdc.energy.gov/vehicles/how-do-gasoline-cars-work#:~:text=A%20gasoline%20car%20typically%20uses,spark%20from%20the%20spark%20plug.
  3. Sources of Greenhouse Gas Emissions | US EPA. (2015, December 29). US EPA. Retrieved from: https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions#transportation
  4. Cage, F. (2022, February 7). The long road to electric cars in the U.S. Reuters. Retrieved from: https://graphics.reuters.com/AUTOS-ELECTRIC/USA/mopanyqxwva/
  5. Biodiesel Basics. (2018). Default. Retrieved from: https://www.biodiesel.org/what-is-biodiesel/biodiesel-basics
  6. Potier, B. (2004, March 4). Goodbye black smoke, hello green transit. Harvard Gazette; Harvard Gazette. Retrieved from: https://news.harvard.edu/gazette/story/2004/03/goodbye-black-smoke-hello-green-transit/
  7. OEM Information. (2022). Default. Retrieved from: https://www.biodiesel.org/using-biodiesel/oem-information
  8. Miller, B. (2016, March 30). 10 Big Pros and Cons of Biodiesel. Green Garage. Retrieved from: https://greengarageblog.org/10-big-pros-and-cons-of-biodiesel
  9. Durrant, C. (2016, May 10). Biodiesel one slick solution, but more to come. Harvard Gazette; Harvard Gazette. Retrieved from: https://news.harvard.edu/gazette/story/2016/05/biodiesel-one-slick-solution-but-more-to-come/