Ultrasound-assisted production of biodiesel and ethanol from spent coffee grounds

•Use of spent coffee grounds as source for production of biodiesel and ethanol.•Study of the ultrasound-assisted extraction of spent coffee grounds oil.•Biodiesel production by ultrasound-assisted esterification reaction.•Study of the hydrolysis of the oil free spent coffee ground.•Ethanol production by Saccharomyces cerevisiae using the hydrolysate. This study evaluates the production of biodiesel and ethanol from spent coffee grounds (SCG). The extraction of oil from SCG, biodiesel production and ethanol production processes were studied. The liquid-to-solid ratio and temperature were evaluated in the ultrasound-assisted extraction of the oil from SCG. The highest yield (12%) was obtained using 4mLg−1 liquid-to-solid ratio at 60°C for 45min. The process to produce biodiesel showed a yield of 97% into fatty acid methyl esters (FAME). The highest glucose yield (192mggSCG−1) was obtained by hydrolysis with 0.4molL−1 sulfuric acid at 121°C for 15min. The hydrolysate was used as fermentation medium for ethanol production by Saccharomyces cerevisiae obtaining 19.0gL−1 at 10h of process of ethanol with a yield of ethanol and productivity of 0.50gg−1 and 1.90gL−1h−1, respectively. Spent coffee grounds were considered a potential feedstock for biodiesel and ethanol production.