| Sumario: | 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 wastewith high fat and oil contents. Furthermore, spent coffee grounds contain a proper fat ratio and arecommercial 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 coffeegrounds 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 wereesterifed at 60 °C and 100 rpm using different reaction conditions. The best reported conditionswere a 0.7% H2SO4 concentration and RMG:MeOH at 1:6 for 120 min, wherein acidity decreased below1%, converting 94.92% of the FFA to methyl esters. Moreover, they underwent a transesterifcationprocess using KOH (1.5% m/v) in the presence of methanol (RMG:MeOH = 1:15) at 60 °C and 100 rpmfor 30 min. The biodiesel was separated by decantation and purifed by successive washing withacidifed 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 D6751 and EN 14214 standards.
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