Each component of the combined yard trimmings had distinctive characteristics (Table 1). Among them, the lawn grass had the highest methane potential, probably due to the high extractives and cellulose contents, as well as the lowest lignin content (Lin et al., 2015). In contrast, wood chips and maple leaves were relatively hard to degrade due to the high lignin content (Liew et al., 2012). It is noteworthy that all feedstocks had acidic pH, which can consume the digester alkalinity and
