Effect of Solvent Extraction Parameters on the Recovery of Oil From Spent Coffee Grounds for Biofuel Production

Abstract

Spent coffee grounds (SCG) are a potentially valuable source of lipids for sustainable production of biofuels. However, there are several feedstock properties and solvent extraction parameters that can impact on the oil yield and quality, potentially reducing the possible environmental benefits of deriving oils from this waste stream. This study presents results of laboratory and pilot plant scale experimental investigations into lipid recovery from spent coffee, determining the effects of solvent extraction variables including duration, SCG-to-solvent ratio and SCG residual moisture. SCG samples from both the industrial production of instant coffee and retail coffee shops were characterized in terms of moisture content, particle size distribution and oil content to identify the impact of these variables on the efficiency of lipid recovery by solvent extraction. The dry weight oil content of the instant SCG samples ranged from 24.2 to 30.4% w/w, while the retail SCG samples contained considerably lower amounts of lipids with their oil content ranging between 13.4 and 14.8% w/w. The highest oil yields were found at an extraction duration of 8 h, while a moisture content of ~2% w/w led to increased yields relative to completely dry samples. A pattern of increasing acidity with decreasing extraction duration was observed, suggesting preferential extraction of free fatty acids (FFA), with the fatty acid (FA) profile of the oil found to be similar to lipids commonly utilized for biofuel production.

Antifungal activity of Piper cubeba L. extract on spoilage fungi isolated from tomato, grapes and lemon

“…As in this study, the berries were soaked in higher concentration of methanol and longer soaking duration. According to Efthymiopoulos et al (2019), the extraction within short period of time period does not permit sufficient time for the solvent to recirculate the extract of total available oil in plant extract compounds. The statement also supported by previous study which asserted that the longer the solvent-sample soaked duration, the more efficient the extraction (Lawson et al, 2010).…”

Transesterification of high-acidity spent coffee ground oil and subsequent combustion and emissions characteristics in a compression-ignition engine

“…This paper presents both the transesterification of oil extracted at industrial scale from SCGs of the instant coffee industry [16], and the subsequent testing of the obtained biodiesel in a modern diesel engine. The effect of various transesterification parameters on the yield and quality of biodiesel derived from SCG oil containing high FFA content are investigated through a two-step method.…”

“…The samples tested in the engine included raw SCG oil extracted at pilot plant scale from instant SCGs [16], SCG neat biodiesel produced from the same raw SCG sample according to the method described in Section 2.2, neat commercial soya and rapeseed biodiesel, and blends of the aforementioned biodiesel samples with a reference fossil diesel of zero FAME content containing 7% v/v and 20% v/v FAMEs.…”

From Coffee to Biodiesel—Deep Eutectic Solvents for Feedstock and Biodiesel Purification

“…Methods for oil extraction were explored, for example, batch extraction with organic solvents such as methanol, ethanol, n-hexane, iso-propanol, etc. and Soxhlet extraction with the aforementioned solvents and their mixtures in different ratios [3,14,15]. The drying kinetics of wet WCGs was investigated in [16] and in situ transesterification has also been investigated, skipping the oil extraction process and synthesizing biodiesel directly from waste coffee grounds [17][18][19][20][21].…”