Oil Extraction from Spent Coffee Grounds: Experimental Studies and Exergoeconomic Analysis

Currently, the spent coffee grounds (SCGs) are considered an agro-industrial waste with a high oil content that can be used as a feedstock in biorefineries. Therefore, the oil extraction from SCGs is considered a main stage, that should be sustainable and low-cost. The aim of this study is to determine and compare the exergetic and economic indicators of two SCGs oil extraction processes: soxhlet extraction (SE) and ultrasound-assisted extraction (UAE). The exergoeconomic balances were performed by using Engineering Equation Solver (ESS). In addition, the effects of the solvent to SCGs ratio on the extraction yield and on the exergoeconomic indicators were studied. The analysis aided by computational tools determined that the exergy destruction rate of the SE process (14.3 kJ/kg) is higher compared with the UAE process (4.50 kJ/kg). Therefore, the oil specific cost is reduced to 86% when using UAE process. Furthermore, in the UAE process, the increase in the hexane to SCGs ratio from 5 mL/g to 20 mL/g, reduces the oil specific cost by 68.5 % and increases the oil extraction yield from 10.5 % to 18.8 %. Future studies should focus on the ultrasound-assisted extraction process scale-up

Simulation and Exergoeconomic Analysis of a Trigeneration System Based on Biofuels from Spent Coffee Grounds

Biofuels have become a source of renewable energy to offset the use of fossil fuels and meet the demand for electricity, heat, and cooling in the industrial sector. This study aims to (a) develop a simulation of a trigeneration system based on a gas turbine cycle and an absorption chiller unit, using biomass and syngas from spent coffee grounds (SCGs) to replace the conventional system currently supplying the energy requirements of an instant coffee plant located in Guayaquil, Ecuador, and (b) carry out an exergoeconomic analysis of the simulated system to compare the effects of different fuels. The results showed an increase in the exergetic efficiency from 51.9% to 84.5% when using a trigeneration system based on biomass instead of the conventional non-integrated system. Furthermore, the biomass-based system was found to have the lowest operating costs ($154.7/h) and the lowest heating, cooling, and power costs ($10.3/GJ, $20.2/GJ, and$23.4/GJ, respectively). Therefore, the results of this analysis reveal that using SCGs as biofuel in this instant coffee plant is feasible for producing steam, chilled water, and power