Scientists Turn Coffee Grounds Into Biodiesel Fuel

What if your morning coffee could help power your car? According to a study by researchers at the University of Nevada, the leftover grounds from your daily brew might have a second life as a source of biofuel — specifically, biodiesel to run diesel engines.

Yes, scientists have confirmed that used coffee grounds can be turned into biodiesel. Using a simple chemical process, they extracted enough oil from spent grounds to produce more than 340 million gallons of biodiesel per year globally — all from coffee waste that’s already being thrown away.

How Researchers Extracted Oil From Coffee Waste

The study, led by engineering professors Mano Misra, Narasimharao Kondamudi, and Susanta Mohapatra at the University of Nevada, focused on spent coffee grounds — the leftover puck-like material from brewed coffee. They collected 50 pounds of used grounds from Starbucks locations, dried them in an oven, and then used a chemical solvent to extract the oils. The process is relatively straightforward and allows the solvent to be reused, while the remaining solid waste can serve as fertilizer, ethanol feedstock, or fuel pellets.

How Much Biodiesel Can Coffee Actually Produce?

Globally, more than 16 billion pounds of coffee are produced annually. Those beans leave behind coffee grounds that contain between 11% and 20% biologically derived oils. Based on that, researchers estimated that coffee waste could yield over 340 million gallons of biodiesel every year. While that sounds like a lot, it’s still less than 1% of the diesel used in the United States each year.

Why Coffee Oil Is a Viable Biofuel — And Its Limits

The extracted coffee oil contains around 15% bio-oil, which is lower than oils from soybeans, rapeseed, or palm. However, coffee-derived oil is more chemically stable due to its higher antioxidant content. The energy required to process it is also relatively low. Researchers estimated the resulting biodiesel could be sold for around $1 per gallon. One unexpected bonus? Cars running on coffee biodiesel may emit a faint coffee aroma.

Still, there’s a major hurdle: collecting enough used coffee grounds efficiently at scale. The team planned to test a small pilot system the following year, sourcing grounds exclusively from Starbucks stores, but even a worldwide effort using every coffee ground wouldn’t make a major dent in global diesel consumption.

Frequently Asked Questions

How much biodiesel can be made from coffee grounds each year?

Researchers estimate that global coffee production yields over 16 billion pounds of beans annually, leaving behind grounds that contain 11–20% bio-oil. This waste could produce more than 340 million gallons of biodiesel per year.

What chemical process is used to extract oil from coffee grounds?

Scientists oven-dried used coffee grounds and then used a reusable chemical solvent to extract the oil. The leftover solids can be repurposed as fertilizer, ethanol feedstock, or fuel pellets.

Is coffee biodiesel as efficient as other biofuels?

Coffee oil contains about 15% bio-oil, which is less than oils from soy, rapeseed, or palm. But it is more stable due to higher antioxidant levels, and the extraction process uses relatively little energy.

How much does coffee biodiesel cost to produce?

The study estimated that biodiesel made from coffee grounds could be produced and sold for around $1 per gallon.

Can coffee biodiesel replace regular diesel fuel?

No. Even if all the coffee grounds in the world were used, the resulting biodiesel would still supply less than 1% of the diesel used in the U.S. each year.

Does coffee biodiesel change how a car smells?

Yes. Cars running on coffee biodiesel may emit exhaust that smells faintly of coffee.

Recommended FrontStreet Beans for Brewing & Sustainability

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