Posted in | Biofuels | Sustainability

New Technique to Convert Used Coffee Grounds into Cleaner Biofuels

Future cappuccino, Americano and latte consumers could help produce the raw material needed for a greener biofuel that would in turn decrease man’s dependence on diesel from fossil fuels.

Purpose-grown feedstocks (used to extract oils) for biodiesels are questionable because of their cost and the demand they put on water and land. However, used coffee grounds, which have a high calorific value, provide a good cost-effective alternative feedstock. However, a lot of the used coffee grounds are at present just dumped. In 2014 over nine million tonnes of used coffee grounds were thrown into landfill.

Only a meager number of businesses are using used coffee grounds to produce biofuels. A team of researchers at Lancaster University have discovered a technique to considerably increase the efficiency of the process, thus hugely increasing biofuel from coffee's commercial competitiveness.

The researchers have combined the existing multi-stage process into a single step (known as in-situ transesterification), which incorporates extraction of the oils from the used coffee grounds and the transformation of it into coffee biodiesel.

In the traditional process, manufacturers blend used coffee grounds with hexane and cook the mixture at 60 °C for about 1 to 2 hours. Once the hexane evaporates, only the oils are left behind. Methanol and a catalyst are then added to create biodiesel and a glycerol by-product - which also requires separating.

The Lancaster team led by Dr Vesna Najdanovic-Visak realized that they could combine the processes by using only methanol and a catalyst - eliminating the need for hexane totally, and therefore saving on chemical waste. Furthermore, they also discovered that the optimum time for the process was 10 minutes to obtain the same yield of oils from the used coffee grounds - a substantial reduction in time and associated energy costs.

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,"  "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.

Dr Vesna Najdanovic-Visak, Lancaster University

The process looks promising and could enable 720,000 tonnes of biodiesel to be produced annually from used coffee grounds.

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