Ken Costello has done an initial oil extraction from the coffee grounds we procured from MonaLou Callery's Cup o' Karma. It turns out that the coffee grounds only contain about 10% oil, and the amount of hexane lost to evaporation exceeds the amount of oil extracted (at least in the small amounts used for his testing) by a factor of 4.5!
To get 15ml of coffee oil Ken lost 70ml of hexane during the extraction process (he recovered 230ml). Since hexane costs about $16 a gallon, plus shipping and hazmat fees, we probably aren't looking at a new feedstock for biodiesel! A lot of the hexane lost was residue in the coffee grounds that evaporated out when the grounds were dried, after extracting the oil. Residual hexane in the coffee oil also reduced the final amount of coffee oil.
Ken will be trying additional extractions to a) see if he can reduce the amount of hexane lost in processing, and b) scale-up the process to get us to a gallon of coffee oil to turn into biodiesel.
You can check out Ken's full write up of his experiment on his Chemistry Land website.
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