Abstract
Climate change is increasingly threatening coffee production systems, intensifying the need for sustainable valorisation pathways for coffee-derived residues. Among these, coffee cut stems (CCS) generated during pruning activities remain largely underutilized, particularly their fine particle-size fraction, which is unsuitable for thermochemical conversion routes. This study evaluates the biochemical methane potential (BMP) of untreated fine CCS (<0.25 mm) under mesophilic anaerobic digestion conditions, aiming to quantify their biomethane yield and assess their role within integrated coffee biorefinery schemes. Batch BMP assays were conducted using three Inoculum-to-substrate ratios (ISR = 0.5, 1.0, and 1.5), without pretreatment or chemical supplementation. Results showed methane yields between 125 and 167 mL CH4/g Volatile Solids (VS), with no statistically significant effect of ISR. Despite moderate biodegradability, the fine CCS fraction demonstrated measurable biomethane production, providing quantitative evidence that anaerobic digestion can complement thermochemical routes by enabling energy recovery from otherwise problematic residues.
