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Researchers Find ‘Early-but-Promising’ Results Converting Coffee Grounds to Biodiesel

The scientific pursuit to find a use for expired coffee grounds continues.

Recently we have seen coffee grounds booze (safe for human consumption!) as well as coffee grounds socks (moisture wicking!). Now researchers at the University of Cincinnati say they have made some “early-but-promising” discoveries related to converting coffee grounds to biodiesel fuel. They say converted triglycerides from grounds might one day present a cheaper, cleaner fuel source for cars and furnaces.

Yang Liu, a graduate student in environmental engineering has been leading the research since 2010, and is this week presenting the findings at the American Chemical Society’s 246th National Meeting & Exposition in Indianapolis.

Yang Liu at the University of Cincinnati

Yang Liu at the University of Cincinnati

Research involved gathering waste coffee grounds from a UC campus Starbucks store in a bucket, removing the oil from the waste coffee grounds, and converting triglycerides (oil) into biodiesel and the byproduct, glycerin. The coffee grounds were then dried and used to purify the biodiesel they derived from the waste coffee grounds.

The preliminary results showed that the oil content in the waste coffee grounds was between 8.37-19.63 percent, and that the biodiesel made from coffee oil meets the ASTM International D6751 standard. That standard is for biodiesel fuels that can be mixed with middle distillate fuels, such as diesel. Researchers also found that using the grounds as a purification system was not as effective as the use of commercial purification products, but suggesting some promising results should warrant future research.

Reasons the researchers explored coffee grounds as a potential fuel source are because coffee grounds represent some 1 million tons in the landfill waste stream each year in the United States, and they are not sought after as a food source, as are other biodiesel-producers such as corn and soy.


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