A bit of the world’s biodiesel may eventually come from Juan Valdez rather than the Exxon Valdez if a pilot project at the University of Nevada at Reno pans out as planned.
Manoranjan Misra, a professor in the university’s department of chemical and materials engineering, is leading a team that recently published a study in the Journal of Agricultural and Food Chemistry on the use of spent coffee grounds as a “versatile” oil source for biofuel.
The Reno team’s paper describes an approach to extract oil from spent coffee grounds and to further transesterify the processed oil to convert it into biodiesel. Using Arabica or Robusta coffee varieties, they wrote, the process yields 10 to 15 per cent oil depending on the coffee species.
The team hopes to assemble a small pilot plant to produce and test the fuel within the next six to eight months, according to an article on the same topic at the website of the magazine Biofuels Business.
According to a report on the study on Scientific American’s website, out of the 16 billion-plus pounds of coffee produced globally each year, the grounds could yield as much as 340 million gallons of biodiesel.
To put that in perspective, the magazine said, the U.S. Department of Energy pegs that country’s annual diesel consumption at about 40 billion gallons a year.
While coffee grounds’ oil yield would be comparable to palm or soybeans, coffee also carries a high proportion of antioxidants that would give coffee-based biodiesel a longer shelf life than biofuels made from other oils.
“The biodiesel derived from the coffee grounds (100 per cent conversion of oil to biodiesel) was found to be stable for more than one month under ambient conditions,” the researchers wrote. The coffee-based biodiesel also carries a coffee aroma, Scientific American said.
Furthermore, the magazine noted, coffee grounds have the added advantage in biofuel production of not also being a food source, such as canola, corn, soybeans, palm or wheat.
Coffee grounds for the Reno study were donated by U.S.-based coffee chain Starbucks. Scientific American quoted the researchers as estimating that Starbucks’ U.S. operations alone could turn a profit of US$8 million per year from the process, assuming there’s a market for both the biodiesel and the leftover byproducts.
“The coffee grounds after oil extraction are ideal materials for garden fertilizer, feedstock for ethanol, and as fuel pellets,” the researchers wrote.
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