Spent Coffee Grounds Alkaline Pre-treatment as Biorefinery Option to Enhance their Anaerobic Digestion Yield

Spent coffee grounds (SCGs) are potentially optimal substrates for methane production but the content of organic compounds refractory to anaerobic digestion reduces the yield of the process. Alkaline pre-treatment was applied to enhance the methane recovery from SCGs through anaerobic digestion. NaOH was applied with different loadings, namely 2, 4, 6, 8% w/w for 24 h, to assess the efficiency of the process and the optimal amount of the basifying solution applied. The highest concentration of NaOH (8% w/w) lead to the best anaerobic digestion performances (392 mLCH4/gVS) as a consequence of the slightly higher lignin degradation which was 24% higher than that of the untreated substrate, and of the higher dissolved organic carbon concentration.