Gasification Product Characteristics from Torrefied Spent Coffee Grounds in A Fixed-Bed Reactor

Abstract

Biomass resources, particularly spent coffee grounds (SCG), offer promising potential for renewable energy generation via gasification. However, the inherent limitations of raw SCG, including high moisture and volatile content, necessitate pretreatment to enhance its suitability as a feedstock. This study evaluates the effectiveness of torrefaction as a thermal pretreatment method for SCG prior to steam gasification in a fixed-bed reactor. Comparative analyses of untreated and torrefied SCG revealed significant improvements in fuel characteristics, with torrefaction at 250 °C for 60 minutes reducing moisture content from 8.35% to 0.74%, volatile matter from 78.7% to 76.32%, and increasing fixed carbon from 12.71% to 21.74%. Optimal gasification performance was achieved at 850 °C and a holding time of 50 minutes, yielding 85.06% bio-gas, with minimal char (12.84%) and tar (2.10%) production. Characterisation of the resulting biochar indicated an increase in fixed carbon and a reduction in moisture, both of which are beneficial for syngas generation. Tar's functional group analysis revealed a high concentration of aliphatic C-H bonds, suggesting it could serve as a biofuel alternative.