Direct biodiesel production from wet spent coffee grounds

Abstract

Utilization of waste spent coffee grounds (SCG) remains limited and requires pre-treatment before being discarded to avoid pollution to the environment. Lipids contained in SCG could be converted to biodiesel through an in situ transesterification method. Current in situ transesterification of wet SCG biomass, conducted at high reaction temperature to reduce the water effect and reduce reaction time, is energy intensive. A new approach, which combines simultaneous extraction-transesterification in a single step using soxhlet apparatus, was developed to produce biodiesel directly from wet SCG biomass. A homogeneous base catalyst at a concentration of 0.75 M showed better catalytic activity than acid, with hexane as a co-solvent on fatty acid (FA) extraction efficiency and FA to fatty acid methyl ester (FAME) conversion efficiency. Studying the factorial effect of ratio of methanol to hexane and reaction time led to the highest FA to FAME conversion efficiency of 97% at a ratio of 1 : 2 and 30 min reaction time. In addition, the catalyst could be used five times without losing its activity. In term of energy consumption, the reactive extraction soxhlet (RES) method could save 38-99% of energy compared to existing methods.

Optimization of the in Situ Transesterification of Grain Sorghum (Milo) DDGS to Fatty Acid Methyl Esters and Fatty Acid Ethyl Esters

“…These results suggest that the addition of MTBE unexpectedly compromised the esterification of the AG within sorghum DDGS. While this solvent combination was successful for previously cited research (Sakthivel et al, 2013; Tarigan et al, 2019), the MTBE may be interfering with some components of our reaction mixture that affects esterification to the extent that larger quantities of methanol (RC 17–20) are required to overcome its effect. RC 17 and 18 gave good yields; however, there is no benefit to adding MTBE as a co‐solvent in the IST reaction of milo DDGS to FAME.…”

“…Studies have shown that using a co‐solvent can improve the conversion of AG to FAME by removing the mass transfer resistance created at the interface of the oil and alcohol, resulting in greater miscibility at the interface and higher reaction rates. Examples cited in the literature include improving the IST conversion of the AG in spent coffee grounds to FAME from 77% to 89% (Tarigan et al, 2019) and up to a 20% increase for the conversion of Jatropha curcas oil to FAME (Sakthivel et al, 2013). To improve upon the 79.8% yield achieved in RC 8 (Table 3), methyl tert‐butyl ester (MTBE) was employed as a co‐solvent (Table 4, RC 15–20).…”

“…To improve upon the 79.8% yield achieved in RC 8 (Table 3), methyl tert-butyl ester (MTBE) was employed as a cosolvent (Table 4,. Duplicating that reaction with the addition of 30% (v/v) and 40% MTBE to the reaction (Table 4, RC 15 and 16), resulted in disappointing yields of 16.1% and 8.6%, respectively, using DDGS subjected to moisture removal at 65 C. Doubling the concentration of (Sakthivel et al, 2013;Tarigan et al, 2019), the MTBE may be interfering with some components of our reaction mixture that affects esterification to the extent that larger quantities of methanol (RC 17-20) are required to overcome its effect. RC 17 and 18 gave good yields; however, there is no benefit to adding MTBE as a co-solvent in the IST reaction of milo DDGS to FAME.…”

“…In that study, the AG conversion peaked at 32.2%. Conversely, several reports demonstrate the utility of the IST method to produce FAME from a variety of feedstocks in significantly higher (> 70%) yields (Dalvi et al, 2012; Haas and Scott, 2007; Pokharkar et al, 2008a, b; Tan et al, 2019; Tarigan et al, 2019; Wyatt et al, 2018).…”

Aqueous enzymatic extraction of palm kernel oil

“…The traditional extraction soxhlet method was used to determine the quantity of palm kernel oil and the result was compared with the AEE. The procedure we followed for the soxhlet extraction has been reported elsewhere (Al-Hamamre et al 2012;Tarigan et al 2019). About 20 g of grounded palm kernel was extracted in the soxhlet apparatus using hexane as an extracting agent under reflux condition for 30 minutes.…”