How Coffee Grounds Can Be Turned Into Biodiesel

Coffee isn’t just your morning fuel — according to a team of American scientists, it might also be your car’s. Researchers from the University of Nevada have demonstrated that used coffee grounds, the same ones you toss in the bin after brewing, can be converted into usable biodiesel.

Yes, those leftover coffee grounds from your daily cup can produce biodiesel. Scientists estimate that global coffee waste could generate more than 340 million gallons of biofuel per year, using a straightforward chemical process.

What’s in Spent Coffee Grounds?

Every year, the world produces over 16 billion pounds of coffee. Those spent grounds still hold value: they contain between 11% and 20% biologically derived oils, also called bio-oils. That’s the key ingredient for making biodiesel.

The Research Behind Coffee-to-Fuel

The study was led by engineering professors Mano Misra, Narasimharao Kondamudi, and Susanta Mohapatra from the University of Nevada. While it’s long been known that coffee contains oils, these researchers were the first to scientifically analyse spent coffee grounds and develop a method to extract the oil for biodiesel production.

The team collected 50 pounds of used coffee grounds from several Starbucks locations. They dried the grounds in an oven and then used a chemical solvent to extract the oil. Importantly, the solvents used can be reused, and the leftover material can serve multiple purposes: as fertiliser, ethanol feedstock, or solid fuel pellets.

How Much Biodiesel Can Coffee Produce?

The extracted oil content in the coffee grounds was around 15%, lower than oils from soybeans, rapeseed, or palm. But coffee oil has advantages: it is more chemically stable due to higher antioxidant content. The researchers estimated that producing biodiesel this way requires relatively low energy input, and could be sold at approximately $1 per gallon.

Challenges to Scaling Up

Despite its promise, the process faces a major hurdle: collecting enough coffee waste efficiently. Currently, there’s no widespread system for gathering used grounds on an industrial scale. The researchers plan to set up a small pilot system next year, sourcing grounds specifically from Starbucks stores and channelling them to a biodiesel plant.

Even under ideal conditions — if all the coffee grounds in the world were used — the resulting biodiesel would still make up less than 1% of the diesel consumed annually in the United States.

Frequently Asked Questions

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

Researchers estimate that global coffee waste could produce over 340 million gallons of biodiesel per year, based on current coffee production levels and the oil content found in spent grounds.

What percentage of oil is in coffee grounds?

Spent coffee grounds contain between 11% and 20% bio-oil, with the research team measuring around 15% oil content in their experiments.

How do scientists extract oil from coffee grounds?

The team dried the used coffee grounds and then used a chemical solvent to extract the oil. This solvent can be reused, and the leftover solids can be repurposed as fertiliser, ethanol material, or fuel pellets.

Is coffee biodiesel as good as other biofuels?

Coffee-derived oil has around 15% oil content, lower than soy or palm oil. However, it is more stable due to higher antioxidant levels, which helps preserve the fuel quality.

Can coffee biodiesel replace regular diesel?

No. Even if all global coffee waste were converted, it would supply less than 1% of U.S. annual diesel use. It’s a supplementary fuel, not a replacement.

Does coffee biodiesel smell like coffee?

Yes, cars running on coffee-based biodiesel may emit exhaust that smells faintly of coffee, adding a unique twist to emissions.