Mano Misra, a professor of engineering at the University of Nevada, Reno, stumbled across a discovery that coffee naturally contains oil as he looked into his leftover coffee cup. Coffee grounds contain 10 to 15 per cent oil by weight and Misra realised that it could be a likely candidate to provide a viable supply of biodiesel. You can make biodiesel at a cost of only 60p per gallon if you reclaim coffee grounds.
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Things you need
- Two 5-gallon buckets of used coffee grounds
- Glass extraction thimble
- Soxhlet extraction apparatus with recovery distillation accessory
Dry the used coffee grounds by thinly spreading them on a clean surface. A couple of hours can be enough to dry the grounds if spread thinly enough.
Separate the coffee grounds from its oil with a Soxhlet extraction apparatus with recovery distillation accessory. Pour a small amount of hexane into the flask on the side of the Soxhlet apparatus.
Boil liquid hexane in the bottom of the flask.
Allow the coffee grounds in the apparatus to fill with hexane five times, which takes about 10 minutes each time. The hexane-coffee oil mixture will become lighter in colour as the oil is separated.
Extract the coffee oil from the hexane and reclaim the hexane by distilling the hexane out of the hexane-coffee oil mixture. Run cold water through the side arm of the apparatus and it will condense the hexane vapour so that it drips into a collection flask on the side of the apparatus.
Surround the collection flask with ice to keep the hexane in a liquid, not gas form.
Tips and warnings
- Keep the area very well ventilated.
- Wear protective gear: gas mask, goggles and gloves.
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