Yang Liu, a graduate student in environmental engineering in UC's College of Engineering and Applied Science (CEAS), used a three-pronged approach to converting waste coffee grounds into energy sources including biodiesel and activated carbon by extracting oil from the waste, drying the waste coffee grounds after oil removal to filter impurities in biodiesel production and burning what was left as an alternative energy source for electricity, similar to using biomass.
The researchers launched the project in 2010, gathering waste coffee grounds in a five-gallon bucket from a Starbucks store on UC's campus. After collection, they removed the oil from the waste coffee grounds and converted triglycerides (oil) into biodiesel and the byproduct, glycerin. The coffee grounds were then dried and used to purify the biodiesel they derived from the waste coffee grounds.
The preliminary results showed that the oil content in the waste coffee grounds was between 8.37-19.63 percent, and biodiesel made from coffee oil meets the ASTM International D6751 standard.
The efficiency of using the waste coffee grounds as a purification material to remove the impurities in crude biodiesel, such as methanol and residual glycerin, was slightly lower compared with commercial purification products. However, the researchers report that results still indicate a promising alternative, considering the cost of purification products.
Compared with petroleum diesel, the cleaner-burning biodiesel reduces the emission of carbon monoxide, hydrocarbons and particular matters (PM).
The researchers say the method they're exploring to produce biodiesel would not only open landfill space, but it also holds promise in creating biodiesel from a natural product.
The study was presented at the National Meeting and Exposition in Indianapolis.