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Clean Techn Environ Policy (2014) 16:14231430
DOI 10.1007/s10098-014-0773-0
ORIGINAL PAPER
Spent coffee grounds for biodiesel production and other applications
Ndia S. Caetano Vnia F. M. Silva
Ana C. Melo Antnio A. Martins
Teresa M. Mata
Received: 24 December 2013 / Accepted: 28 April 2014 / Published online: 17 May 2014 Springer-Verlag Berlin Heidelberg 2014
Abstract This work evaluates the possibility of using spent coffee grounds (SCG) for biodiesel production and other applications. An experimental study was conducted with different solvents showing that lipid content up to 6 wt% can be obtained from SCG. Results also show that besides biodiesel production, SCG can be used as fertilizer as it is rich in nitrogen, and as solid fuel with higher heating value (HHV) equivalent to some agriculture and wood residues. The extracted lipids were characterized for their properties of acid value, density at 15 C, viscosity at 40 C, iodine number, and HHV, which are negatively inuenced by water content and solvents used in lipid extraction. Results suggest that for lipids with high free fatty acids (FFA), the best procedure for conversion to
biodiesel would be a two-step process of acid esterication followed by alkaline transesterication, instead of a sole step of direct transesterication with acid catalyst. Bio-diesel was characterized for its properties of iodine number, acid value, and ester content. Although these quality parameters were not within the limits of NP EN 14214:2009 standard, SCG lipids can be used for biodiesel, blended with higher-quality vegetable oils before transesterication, or the biodiesel produced from SCG can be blended with higher-quality biodiesel or even with fossil diesel, in order to meet the standard requirements.
Keywords Biodiesel Fertilizer Lipid extraction Solid
fuel Spent coffee grounds
Introduction
Biodiesel is a renewable fuel that is being increasingly used in Europe, alternatively or in addition to fossil diesel, with the main goals of reducing the dependence on fossil fuels in the transportation sector, and increase fuel renewability with positive impacts in the environment (Mata et al. 2013). Its production involves a transesterication, a reversible reaction with three successive steps, where triglycerides are converted to diglycerides, diglycerides to monoglycerides, and monoglycerides to esters and glycerol. From this reaction, it results in three moles of fatty acid monoalkylester (biodiesel) and a mole of glycerol...