Kinetics of extraction and in situ transesterification of oils from spent coffee grounds

Abstract

Resource limits, environmental concerns and unstable petroleum costs have led to an increased effort to develop alternative liquid fuels. Purpose grown feedstocks are expensive and demand additional resources such as land and water. Spent coffee grounds (SCGs) are a good potential low-cost feedstock, however, processing times and costs must be lowered in order to be cost competitive with fossil fuels.In this work, we investigated the kinetics of oil extraction from SCGs to explore if current methods of oil extraction could be hastened and an integrated process which couples oil extraction and conversion to biodiesel stages in one single step (in situ transesterification) which could significantly cut down biodiesel production costs.Kinetics of oil extraction from SCGs using n-hexane as solvent was studied as a function of temperature, solvent to solid ratio and water content. We have found that oil extraction times could be significantly reduced to 10 minutes due to high diffusion coefficients. Further, we demonstrate, for the first time, the successful in situ transesterification of SCGs using different concentration of sodium hydroxide as catalyst and methanol to oil mole ratio, promising lower biodiesel production costs from a ubiquitous waste product around the world.

Brewers' spent grains: Drying kinetics and biodiesel production

“…It is important to note that the oil content of BSGs ranges from 3.9% to 13.3% on dry bases [the same as above??] which is comparable with the oil content found in the other feedstocks such as 20% in Jatropha curcas (Sinha et al, 2015), 14% in spent coffee grounds (Najdanovic-Visak et al, 2017) and other agricultural waste including seeds of tea, tobacco or tomato, linseed and bay laurel leaves (Rehan et al, 2017).…”

“…However, decrease in the yield was observed with further increase of the ratio (Fig.6). This trend is well documented to other in situ transesterification, such as that from the spent coffee grounds (Najdanovic-Visak et al, 2017) and from Jatropha curcas (Kasim and Harvey, 2011). Initial yield increase is due to higher concentration of methanol favouring the biodiesel production while further increase in amount of methanol dilutes triglycerides leading to lower reaction rates.…”

“…On the contrary to the traditional method comprising of oil extraction, solvent evaporation and chemical conversion of oils to biodiesel, in situ transesterification offer a one pot operation where extraction and transesterification occur simultaneously. Several studies have employed this method for various kinds of biomass such as algae (Kim et al, 2015, Haas andWagner, 2011), rapeseed (Qian et al, 2013), Jatropha (Kasim and Harvey, 2011), spent coffee grounds (Park et al, 2006;Najdanovic-Visak et al, 2017), soy flakes (Haas et al, 2004), etc.…”

Effect of Ecofriendly Bio-Based Solvents on Oil Extraction From Green Coffee Bean and Its Industrial Press Cake

“…It is generally reported that the extraction rate increases with increasing temperature and liquid/solid ratio, and decreasing particle size; however, these parameters shall be extensively studied, since high temperatures may favor the extraction yield of solids and disfavor the recovery of phenolic compounds and antioxidants (Torun et al, 2015). Earlier works reported the extraction efficiency of different coffee species by using different extraction methods, such as, conventional (n-hexane, water, anhydrous and hydrous ethanol, methanol and their mixtures) (Bravo et al, 2013;Najdanovic-Visak et al, 2017;Somnuk et al, 2017), pressurized liquid (water, ethanol, and methanol) (Belandria et al, 2016;Oliveira et al, 2018), ultrasound assisted (ethanol) (Al-Dhabi et al, 2017), supercritical CO 2 (De Marco et al 2018;Getachew et al, 2018), and microwave extraction (petroleum ether) (Tsukui et al, 2014). However, there is no reported study on the organic solvent extraction behavior of total soluble solids from green coffee beans and its press cake in order to state the feasibility of mechanical oil extraction.…”

Use of the Product from Low Pressure Extraction (Crambe Seed Oil and Methyl Acetate) for Synthesis of Methyl Esters and Triacetin Under Supercritical Conditions

“…In this case, the material containing the oil is kept in direct contact with the reagent acting in both the extraction and the reaction. [ 9–12 ] The use of this integrated process (extraction followed by reaction) eliminates the need for separation, oil purification and solvent recovery and significantly reduces the processing time. [ 13,14 ] The elimination of these steps allows the overall process of biodiesel production to be simplified, making it economically attractive.…”