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Author(s): Nídia S.Caetano
Vânia F. M. Silva
Teresa M. Mata
Title: Valorization of coffee grounds for biodiesel production
Issue Date: 2012
Abstract: This work evaluates the use of spent coffee grounds (SCG) for biodiesel production. The SCG werecharacterized for their moisture content (12.1 wt%), total carbon (TC) and total nitrogen (TN) (52.2 and2.1 wt% respectively), cellulose and total lignin contents (33.6 wt% and 13.8 wt% respectively),carbon/nitrogen mass ratio (C/N = 24.8) and higher heating value (HHV, of 19.3 MJ/kg). For extractingthe oil from the SCG, several solvents were tested at different contact times: hexane, ethanol,isopropanol, heptane and a mixture of hexane/isopropanol in the proportions of 50:50; 60:40; 70:30and 80:20 (vol/vol). Results revealed an oil content ranging from 6.3 to 28.3 wt%, depending on theextraction conditions. For example, using hexane/isopropanol (50:50, vol/vol) a 21.5 wt% of oilrecovery was obtained after 3 h of contact time, while using isopropanol a 21.0 wt% of oil recovery wasobtained in 6.8 h, but at higher operating cost, considering the energy and solvent consumption.Regarding the oil characterization the following parameters can be highlighted: HHV of 36.4 MJ/kg,iodine value of 54.4 (g I2)/(100 g oil), water content of 2004 ppm and acid value of 118.4 (mg KOH)/(goil). Finally, the possibility of using the recovered coffee oil for biodiesel production was evaluated. Inthis regard it was performed the oil esterification in three consecutive steps (using 1% of H2SO4 and 40% of methanol for 2 h of reaction time at 60 ºC and 500 rpm) followed by one transesterification step (1% of NaOH and 40 % of methanol during a 2 h reaction time at 60 ºC and 500 rpm). The resultingbiodiesel was characterized for its acid value, density, viscosity at 40 ºC, iodine value and esterscontent (65.7 to 72.9 %), of which only the iodine value of 26 and 58.4 (g I2)/(100 g biodiesel) waswithin the NP EN14214:2009 standard limits. The reaction yield varied between 58.8 and 62.2 wt%.Results suggest the need for a further process optimization in order to obtain a biodiesel complyingwith this standard quality requirements.
Subject: Ciências Tecnológicas, Outras ciências da engenharia e tecnologias
Technological sciences, Other engineering and technologies
Scientific areas: Ciências da engenharia e tecnologias::Outras ciências da engenharia e tecnologias
Engineering and technology::Other engineering and technologies
Related Information: info:eu-repo/grantAgreement/FCT - Fundação para a Ciência e Tecnologia/Programa de Financiamento Plurianual de Unidades de I&D/FCOMP-01-0124-FEDER-022677/PROJECTO ESTRATÉGICO - UI 511 - 2011-2012/PEst-C/EQB/UI0511/2011
Document Type: Artigo em Revista Científica Internacional
Rights: restrictedAccess
Appears in Collections:FEUP - Artigo em Revista Científica Internacional

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