Effluent from a mesophilic liquid anaerobic digester feeding
with sewage sludge operated by Schmack Bioenergy (Akron, OH,
USA) was used as inoculum for L-AD tests. The Schmack digester
is a continuous stirred-tank reactor with a hydraulic retention time
of 28 days. The effluent was centrifuged at 4000 rpm for 30 min to
increase the total solids (TS) content from 7.6% to 17.7% for SS-AD