Mechanical pretreatment of municipal biowaste to produce an aqueous slurry dedicated to anaerobic digestion

International audienceThis study investigated a wet mechanical pretreatment to improve methane production by anaerobic digestion from biowaste material by separating a biodegradable aqueous slurry fraction (ASF) from a more recalcitrant particulate fraction (PF). Four source-sorted municipal biowaste were studied, namely Household (HBW), Supermarket (SBW), Restaurant (RBW) and Green Biowaste (GBW). The treatment consisted in soaking the waste in water and then press the slurry through a grid with 3-mm openings to separate the 2 fractions. Methane production of ASF and PF obtained from the 4 biowastes were 2 measured using the BMP protocol and compared to the potential of the respective untreated biowaste. Results were very different for GBW as compared to the other 3 BW. With GBW, which was the most lignocellulosic of the BW studied, only 17% of the initial methane potential was recovered in the ASF. The extraction was much better on the other biowastes and increased in the following order: HBW (58%) ≃ RBW (57%) < SBW (67%). The ASF from these biowastes exhibited low total solids contents and high BMPs (416, 408 and 423 NLCH4.g-1 vs for HBW, RBW and SBW respectively). The experimental results obtained in this study therefore showed that wet pressing separation was an efficient pretreatment to improve and facilitate methane production by anaerobic digestion of biowaste such as HBW, RBW and SBW