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

Abstract

Over three billion cups of coffee are consumed daily, making waste coffee grounds readily available throughout the world. Containing approximately 10–15 wt% of oil, they have great potential for biodiesel production. The goal of this work was to produce high quality biodiesel from waste coffee grounds. One fresh and four different types of waste coffee grounds were collected. Oil was extracted by the Soxhlet method with n-hexane and then purified via extractive deacidification with a potassium carbonate-based deep eutectic solvent. Biodiesels were synthesized by means of alkali catalyzed transesterification at different catalyst:methanol:oil mass ratios and reaction times. Impurities present in crude biodiesels were extracted with a choline chloride-based deep eutectic solvent. All batch extraction experiments were performed at room conditions in a small scale extractor. Optimal conditions for synthesis and purification were defined in order to assure high quality of the produced biodiesel. Additionally, continuous column extraction with the choline chloride-based solvent was tested as a purification method for crude biodiesel. Stabilization time and optimal biodiesel to solvent mass ratio were determined. The potassium carbonate-based solvent efficiently reduced the total acid number of the feedstock (deacidification efficiency ranged from 86.18 to 94.15%), while the one based on choline chloride removed free glycerol and glycerides from crude biodiesels. After continuous purification, the purified biodiesel was of excellent quality with glycerol and glyceride contents below the EN 14214 limit.

Review and Perspectives for Effective Solutions to Grand Challenges of Energy and Fuels Technologies via Novel Deep Eutectic Solvents

“…Therefore, it has been probed the use of DESs, mainly choline chloride-based ones for the reduction of glycerol content in biodiesel beyond the regulated limits. 153 Moreover, into a circular economy framework, glycerol waste byproduct from biodiesel synthesis has been proposed as a starting material for the fabrication of DESs, with the produced DES being applied for the subsequent biodiesel purification and upgrading (see Figure 10). 154 Other relevant separation operations considering DESs involve their use as azeotrope breakers.…”

“…Ammonium and phosphonium DESs for glycerol removal from biodiesel were studied by Shahbaz et al probing the largest extraction using phosphonium-based DES with glycerol as HBD. Therefore, it has been probed the use of DESs, mainly choline chloride-based ones for the reduction of glycerol content in biodiesel beyond the regulated limits . Moreover, into a circular economy framework, glycerol waste byproduct from biodiesel synthesis has been proposed as a starting material for the fabrication of DESs, with the produced DES being applied for the subsequent biodiesel purification and upgrading (see Figure ).…”

“…22 In the case of DESs application for the fossil fuels industry, emphasis on specific processes such as fuel desulfurization, gas capture, and separation, has probed their suitability. 23 Over the past few years, DESs and NADESs have been considered for further complicated applications, such as biodiesel production, 24 biomedical and pharmaceutical applications, 25 power systems and battery technologies, 26 biomass processing, 27 nanomaterials synthesis, 28 and water treatment. 29 Gas capture and separation, water treatment, fuel conditioning and desulfurization processes are the most widely utilized chemical process and fuels industries; in addition, to obtain effective and sustainable outcomes from such classical processes, more innovative approaches are essential to complement the existing ones.…”

A Review of the Use of Eutectic Solvents, Terpenes and Terpenoids in Liquid–liquid Extraction Processes

“…Recently, Sander et al (2020) [49] have also applied the eutectic solvents in the synthesis of biodiesel from waste coffee grounds. The eutectic solvent composed of potassium carbonate and ethylene glycol with a 1:10 molar ratio was used in the extractive deacidification of waste coffee grounds oil, obtaining extraction yields of 86−94%, being these values higher than those achieved using the conventional method based on esterification with H 2 SO 4 .…”

Waste-Cooking-Oil Free Fatty Acid Reduction Using Deep Eutectic Solvent as Raw Material of Biodiesel

“…Adsorption was chosen because it is easy to implement and economical [5]. Selection of adsorbents can use chemicals such as bentonite, zeolite, sulfuric acid, solvent extraction and agricultural waste in the form of rice husks, coconut shells, bagasse, rice straw, corn cobs, etc [6]. On the other hands, FFAs reduction could be used reaction temperature and using sodium methoxide solution during transesterification process [7].…”