Abstract

AIELLO-MAZZARRI, Cateryna et al. Generating Biodiesel Using Fats Extracted from Coffee Grounds: Esterification using H ₂ SO ₄ and Transesterification using KOH. Cienc. Ing. Neogranad. [online]. 2019, vol.29, n.1, pp.53-66. ISSN 0124-8170.  https://doi.org/10.18359/rcin.2899.

Finding adequate non-food sources is one of the main challenges while producing biofuels. Particularly for biodiesel, research is focused on using unconventional crops, residues, and waste with high fat and oil contents. Furthermore, spent coffee grounds contain a proper fat ratio and are commercial and domestic waste materials. Therefore, this study assesses biodiesel production using fats extracted from coffee grounds through a two-stage process. The fats extracted from coffee grounds by boiling at reflux using hexane as a solvent presented high acidity at 32.07 ± 0.01% (70.24 ± 0.03 mg KOH/g fat), thereby indicating a high content of free fatty acids (FFA). First, the fats were esterified at 60 °C and 100 rpm using different reaction conditions. The best reported conditions were a 0.7% H2SO4 concentration and RMG:MeOH at 1:6 for 120 min, wherein acidity decreased below 1%, converting 94.92% of the FFA to methyl esters. Moreover, they underwent a transesterification process using KOH (1.5% m/v) in the presence of methanol (RMG:MeOH = 1:15) at 60 °C and 100 rpm for 30 min. The biodiesel was separated by decantation and purified by successive washing with acidified water, resulting in a mixture of methyl esters with linoleic (48.40%), palmitic (36.21%), stearic (8.69%), and oleic (6.69%) acids, whose properties comply with the requirements from the ASTM D 6751 and EN 14214 standards.

Keywords : Coffee Grounds; Biodiesel; Esterification; Transesterification.

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