Location: Bio-oils ResearchTitle: Complete utilization of spent coffee grounds to produce biodiesel, bio-oil and biochar) Author
Submitted to: ACS Sustainable Chemistry & Engineering
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/2/2013
Publication Date: 10/21/2013
Citation: Vardon, D.R., Moser, B.R., Zheng, W., Witkin, K., Evangelista, R.L., Strathmann, T.J., Rajagopalan, K., Sharma, B.K. 2013. Complete utilization of spent coffee grounds to produce biodiesel, bio-oil and biochar. ACS Sustainable Chemistry & Engineering. 1:1286-1294. Interpretive Summary: This research reveals that spent coffee grounds have application as a feedstock for production of biodiesel, bio-oil and biochar. Coffee is one of the largest agricultural commodities traded worldwide, so commercial coffee beverage production generates substantial quantities of spent grounds that generally contribute to landfill waste. The objective of the current study was to utilize this coffee waste for production of useful materials. Lipids extracted from the grounds were converted into biodiesel, which exhibited fuel properties similar to that of soybean oil-derived biodiesel. The solid material left over after lipid extraction was subjected to pyrolysis to yield bio-oil and biochar. Application of the biochar as a soil amendment enhanced the yield of grass (sorghum-sudangrass) by over 2-fold. The bio-oil fraction after catalytic upgrading to lower heteroatom content would be suitable as a feedstock for conventional petroleum refining operations. This research demonstrates the utility of an agricultural waste product for biofuel and agronomic applications, thus enhancing domestic biomass utilization while simultaneously reducing the volume of material added to municipal landfills.
Technical Abstract: This study presents the complete utilization of spent coffee grounds to produce biodiesel, bio-oil and biochar. Lipids extracted from spent grounds were converted to biodiesel to evaluate neat and blended (B5 and B20) fuel properties against ASTM and EN standards. Although neat biodiesel displayed high viscosity, moisture, sulfur, and poor oxidative stability, B5 and B20 met ASTM blend specifications. Slow pyrolysis of defatted coffee grounds was then performed to recover bio-oil and biochar as co-products. The effect of feedstock defatting was examined, and bio-oils analyses included elemental and functional group composition, compound identification, and molecular weight and boiling point distributions. Feedstock defatting reduced pyrolysis bio-oil yields, energy density and aliphatic functionality, while increasing the number of low-boiling oxygenates. The high bio-oil heteroatom content will likely require upgrading. Lastly, biochar derived from spent and defatted grounds was analyzed for its physico-chemical and soil amendment properties. Both biochars displayed similar surface area and elemental makeup. Application of biochar with fertilizer enhanced sorghum-sudangrass yields over two-fold, highlighting biochar’s potential as a soil amendment.