The goal of this research was to create a green chemistry lab for undergraduate students in which they would produce ethanol from spent coffee grounds (SCG). Spent coffee grounds have an advantage over some other plant material because they contain no lignin, and lignin can significantly complicate and lengthen the extraction of sugars. To complete this research, two possible SCG pre-treatments with 12 M sulfuric acid were tested. In the first option, SCG were left in sulfuric acid in a 30 °C incubator overnight. In the second option, room-temperature sulfuric acid was added to the SCG and allowed to sit for ten minutes. Then the mixture was slowly brought to reflux over seven minutes. Samples from both options were refluxed for sixty minutes to complete the sugar extraction. This created a qualitative difference of color during extraction, which may have been indicative of overall sugar yield. Two types of yeast were tested for fermentation of the extracted sugars. Baker’s yeast typically gave gave less than 15% ethanol content; a beer yeast gave results between 15 - 29% as determined by density. Overall, it was found that the best process was to heat up the SCG:acid mixture slowly and ferment with the beer yeast, which is what created the 29% ethanol sample.<br/><br/>

Coffee grounds to ethanol: Green chemistry in the undergraduate lab

253rd National Meeting (2017)

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