Thermal Characterization of Biochars Produced in Slow Co-Pyrolysis of Spent Coffee Ground and Concentrated Landfill Leachate Residue †

Abstract

Resource depletion and climate change have fostered sustainable initiatives in the waste management sector. Pyrolysis (Py) has emerged as an option for valorizing spent coffee grounds (SCG). In addition, inorganic compounds can have catalytic effects on the pyrolytic reaction of organic materials, increasing the char yield and porosity of biochar. This study investigates the slow pyrolysis of SCG using concentrated landfill leachate residue (CLLR) (1:1 wt%) as a pyrolitic additive due to its high salinity. Biochars were characterized based on their thermal behavior to discuss environmental benefits and potential applications. Slow-py experiments were conducted using a lab-scale pyrolizer, and thermal characterization was performed using TA Instruments, specifically the SDTQ600 model. Biochars were characterized by higher water contents and heating rates than those experienced by their feedstocks. It is suggested that the high metal content of CLLR could change the biochar’s thermal stability, decreasing its decomposition temperature. Values were 9.18 wt% and 18.11 MJ kg−1 and 23.25 wt% and 22.05 MJ kg−1 for biochars produced using SCG and SCG and CLLR (1:1 wt%), respectively. Future studies will include biochar ecotoxicity analyses and measure carbon–energy balance.