2. Materials and methods
2.1. Feedstock and inoculum
Highland barley straw, Tibetan pig and cattle manure were collected from the farms located in the campus of Agricultural and Animal Husbandry College of Tibet University with an altitude of 3000 m above mean sea level in Linzhi, China. The collected materials were first dried to a moisture content of less than 10% at room temperature, chopped into small sections and then ground to pass a 40 mesh sieves (0.5 mm pore size). Afterward, they were packed
into polyethylene bags and stored at room temperature until used. The storage time was no more than one week. The inoculum was obtained from a laboratory scale (about 30 L) psychrophilic (15 C) anaerobic digester fed with TPM, CM and BS, and operated as a sequence batch reactor. The physico-chemical characteristics of manures, BS and inoculum are listed in Table 1.