Fluid and Gas Transfer

Breakthrough Makes It Easier to Turn Used Coffee Grounds Into Cleaner Biofuels

11 May 2017

Although not many companies are converting used coffee grounds into biofuels, researchers at Lancaster University hope to increase that number with significant improvements to the process, ultimately reducing our reliance on diesel from fossil fuels.

Currently, the purpose-grown feedstocks used to extract oils for biodiesels are costly and take a toll on both land and water. However, researchers believe that used coffee grounds are a decent low-cost alternative feedstock.

Lancaster University researchers have found a way to consolidate what is typically a multi-stage process into just one step, combining the oil extracts from the used coffee and converting it into coffee biodiesel.

Traditionally, manufacturers mix used coffee grounds with hexane and cook the mixture at 60° C for between one to two hours. The hexane is then evaporated to leave behind the oils. Methanol and a catalyst are then added to make biodiesel and a glycerol by-product—which also needs separating.

The researchers reduced the process by using just methanol and a catalyst—entirely removing the hexane from the process and thereby reducing the amount of chemical waste. Researchers also managed to whittle down the time the process takes to 10 minutes, gaining the same yield of oils from the used coffee grounds.

"Our method vastly reduces the time and cost needed to extract the oils for biofuel making spent coffee grounds a much more commercially competitive source of fuel," said Dr. Najdanovic-Visak, Lecturer in Lancaster University's Engineering Department. "A huge amount of spent coffee grounds, which are currently just being dumped in landfill, could now be used to bring significant environmental benefits over diesel from fossil fuel sources."

The process has the potential to enable 720,000 tonnes of biodiesel to be produced each year from spent coffee grounds.

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