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

Abstract

Spent coffee grounds (SCG) are one of the lignocellulosic biomasses that have gained much attention due to their high potential both in valorization and biomethane production. Previous studies have reported single processes that extract either fatty acids/lignin or biogas. In this study, an integrated physicochemical and biological process was investigated, which sequentially recovers lignin, fatty acid methyl esters (FAME) and biogas from the residue of SCG. The determination of optimal conditions for sequential separation was based on central composite design (CCD) and response surface methodology (RSM). Independent variables adopted in this study were reaction temperature (86.1–203.9 °C), concentration of sulfuric acid (0.0–6.4%v/v) and methanol to SCG ratio (1.3–4.7 mL/g). Under determined optimal conditions of 161.0 °C, 3.6% and 4.7 mL/g, lignin and FAME yields were estimated to be 55.5% and 62.4%, respectively. FAME extracted from SCG consisted of 41.7% C16 and 48.16% C18, which makes the extractives appropriate materials to convert into biodiesel. Results from Fourier transform infrared spectroscopy (FT-IR) further support that lignin and FAME extracted from SCG have structures similar to previously reported extractives from other lignocellulosic biomasses. The solid residue remaining after lignin and FAME extraction was anaerobically digested under mesophilic conditions, resulting in a methane yield of 36.0 mL-CH4/g-VSadded. This study is the first to introduce an integrated resource recovery platform capable of valorization of a municipal solid waste stream.

A shift from anaerobic digestion to dark fermentation in glycol ethylene fermentation

“…Sołowski et al ( 2020b ) observed the presence of coinciding with these two gases. Lee et al ( 2019 ) observed common hydrogen sulphide emission in anaerobic digestion. Shivasankaran et al ( 2020 ) discerned that this emission occurs mostly in high protein substrate due to the necessity of breaking amino acids with sulphur during fermentation.…”

Evaluation of fatty acids, phenolics and bioactivities of spent coffee grounds prepared from Vietnamese coffee

“…For example, the utilization of SCG for productions of bioethanol, butanol, fertilizers and SCG-based sorbent materials for metal removal has been proposed. [3][4][5][6][7] Spent coffee ground is also used for development of skin-whitening products due to its inhibition of tyrosinase activity and melanin synthesis. [8,9] Sufficient amounts of dietary fiber, protein, lipid, and low glycemic sugars in SCG and acceptable rheological properties of SCG-supplemented dough give rise to its application in biscuit products.…”

Organosolv biorefinery: resource-based process optimisation, pilot technology scale-up and economics

“…Afterwards, the extractives were converted to fatty acids (fatty acids methyl esters and omega-3 fatty acids). 23,24…”