Comparative study of biofuel production based on spent coffee grounds transesterification and pyrolysis: Process simulation, techno-economic, and life cycle assessment

Abstract

Biomass is an interesting energy source to replace fossil fuels for carbon neutrality, which is called biofuel. Spent coffee grounds (SCG) have the potential for the biofuel production since it is generated a lot due to the increased coffee consumption, and it has a high heating value. In this study, to evaluate the economic and environmental feasibilities of biofuel from SCG, the feasibilities of biofuel production by transesterification and pyrolysis of SCG were estimated and compared via process simulation, techno-economic analysis, and life cycle assessment. Consequently, the production cost and CO2 emissions of transesterification were 3.08 times and 6.92 times larger than pyrolysis because feedstock pretreatment was necessary before the transesterification and pretreatment efficiency were low. Pyrolysis biofuel had a low 32.18 MJ kg-1 higher heating value compared to the 40.10 MJ kg -1 of transesterification biofuel due to the water contents depending on the cooling temperature of products. By varying efficiency and cooling temperature through the sensitivity analysis, costs became 30.76-43.71 $ GJ-1 and 8.82-12.35 $ GJ-1 for transesterification and pyrolysis, respectively. Although efficiency improved, trans-esterification cost could not overcome pyrolysis because of the additional pretreatment and separation. The CO2 emissions were reduced greatly in the transesterification system while the pyrolysis system gradually increased. Even though the pyrolysis system could emit more CO2 when transesterification efficiency improved, pyrolysis recycling would be proper for the SCG feedstock because of the economic feasibility.