Methane content in biogas from ELES was 62%, whereas in LES was barely a 31%. The theoretical methane production based on sludge composition was estimated, following Buswell's equation [11], in 486 mLCH4/gVS for sludge after lipid extraction.Based on the experimental methane production, biodegradability (expressed as the ratio measured to theoretical methane production) resulted 47% and 4% for ELES and LES, respectively. The 47% of biodegradability is in line with