Effect of Mild-Temperature Thermo-Alkaline Pretreatment on the Solubilization and Anaerobic Digestion of Spent Coffee Grounds

Abstract

Abstract:Mild-temperature thermo-alkaline pretreatment of spent coffee grounds (SCG) was studied to improve its solubilization and methanation. The simultaneous effects of NaOH concentration (0-0.2 M) and temperature (60-90 • C) were investigated. Significant solubilization of SCG was achieved by the pretreatment, particularly under high-NaOH-concentration and high-temperature conditions. However, adding NaOH above a certain concentration adversely affected the methane production. Therefore, the degree of solubilization (SD) correlated poorly with methane yield (Ym). Response surface models of SD and Ym were successfully generated. The maximum response of SD (36.4%) was obtained at 0.18 M NaOH and 90.0 • C, while that of Ym (263.31 mL CH 4 /g COD added) was obtained at 0.13 M NaOH and 70.5 • C. Hydrogenotrophic Methanospirillum species were the dominant methanogens in all the SCG digestion tests. It is likely that NaOH concentration had a more significant influence on the development of microbial community structure, particularly of methanogens than temperature.

Sequential Production of Lignin, Fatty Acid Methyl Esters and Biogas from Spent Coffee Grounds via an Integrated Physicochemical and Biological Process

“…To investigate methane yields of the solid remaining SCG extracted from organosolv treatment in the AD, the values of cumulative methane production were analyzed in BMP tests ( Figure 5). The result was estimated to be 36.0 mL-CH 4 /g-VS added , a relatively low value compared to conventional organic wastes used for methane production [13]. This result was inconsistent with a previous study, which reported that organosolv treatment could improve BMP of lignocellulosic substrate through degrading non-biodegradable lignocellulosic structures into easily digestible materials [40].…”

“…Due to the organic richness of SCG, they have been subjects of anaerobic digestion (AD) in the quest to produce biogas using a sustainable biological approach [9]. SCG are especially rich in sugars, proteins and lipids, comprising 45.3% [10], 13.6% [11] and 9.3-16.2% [12], respectively, of its total weight, which makes SCG attractive subjects of AD research [13]. AD is one of the most favored biological processes that can retrieve energy from solid wastes under anaerobic conditions.…”

“…AD is one of the most favored biological processes that can retrieve energy from solid wastes under anaerobic conditions. During AD processes, organic wastes are broken down from polymers to monomers and eventually to methane, a viable source of energy [13]. Since AD processes are mostly operated under the mesophilic temperature region (30-40 • C), the resource recovery platform needs to be established primarily under mesophilic conditions.…”

Improved Glucose Recovery from Sicyos angulatus by NaOH Pretreatment and Application to Bioethanol Production

“…In lignocellulosic biomass pretreatment process, alkaline concentration is a significant factor affecting degradation of the ester bonds between lignin-carbohydrate matrix [35]. Various study reported that the NaOH was suitable to remove lignin barrier, which increase the accessibility of enzyme to carbohydrate [37][38][39]. Carbohydrates of lignocellulosic biomass were comprised of cellulose and hemicellulose such as glucan, xyloglucan, xylan, arabinoxylan, mannan, gluco-or galactomannan [40].…”

Comparison of pretreatment methods that enhance biomethane production from crop residues - a systematic review

“…Data on combined methods is rather limited. However, combined processes were reported to be fast methods (Kumar and Sharma, 2017;Kim et al, 2018).…”