Enhancement of anaerobic digestion of shredded grass by co-digestion with sewage sludge and hyperthermophilic pretreatment

Anaerobic Codigestion of Grass and Sewage Sludge: Laboratory Experiments and Feasibility Analysis

“…Figure 6 shows the methane production of grass in the batch experiments. The results of the batch experiments (A) are after Wang et al (2014b). The codigestion results from the batch experiments (A) showed that the methane yield of grass in batch experiments (Y GB ) was 0.213, 0.228 and 0.264 NL/gVS-grass in sewage sludge amounts of 0, 1.8 and 3.5 g VS/L-reactor, respectively.…”

“…When the grass was codigested with sludge from WWTP-A, the conversion of grass to methane was difficult to achieve under mesophilic conditions (Wang et al, 2014b). The methane yield was 0.19 NL/g VS-grass under thermophilic conditions that corresponds with a COD-based methane conversion ratio of 40% (Wang et al, 2014b).…”

“…Experiment A-Comparison of Mesophilic and Thermophilic Conditions. Four series of lab-scale continuous stirred tank reactors (CSTR) were operated under mesophilic (35 8C) or thermophilic (55 8C) conditions with grass and mixed sludge (WWTP-A) (RM, RT) and mixed sludge only as controls (RCM, RCT) for 260 days (Wang et al, 2014b). Operational conditions for the continuous experiments are summarized in Table 2.…”

“…To evaluate the effect of codigestion on methane conversion, thermophilic batch codigestion experiments under different substrate concentrations were performed (Wang et al, 2014b).…”

“…An additional energy source is not required here because the waste heat can be used for the treatment. Wang et al (2014b) demonstrated that thermophilic codigestion of sewage sludge and grass was superior to mesophilic 1 Department of Environmental Engineering, Kyoto University, Japan 2 School of Environment, Tsinghua University, China digestion, and a hyperthermophilic (80 8C) pretreatment promoted a methane yield, but detailed information on thermophilic anaerobic co-digestion was not available. In this study, batch and continuous digestion experiments were conducted to assess the feasibility of anaerobic codigestion of sewage sludge and grass.…”