An innovative municipal solid waste separation technology - water separation was developed in China recently. The purpose of this study was to evaluate the feasibility of anaerobic digestion from water sorted organic fraction of municipal solid waste (WS-OFMSW) to methane. A group of bench-scale (35 L) mesophilic (30 + or - 2 degrees Celsius) batch anaerobic digestions were carried out with three total solids in reactor (TSr = 16.0%, 13.5% and 11.0%). The biodegradability of WS-OFMSW with VS/TS of 61.6% was better than that of mechanically sorted OFMSW but still poor than that of source sorted OFMSW. No inhibitions of metal ions, volatile fatty acids and ammonia on anaerobic digestion were found. The reactors with TSr 16.0%, 13.5% and 11.0% achieved methane yield of 273, 283 and 314 L/kgVS and VS removal rate of 26.1%, 35.8% and 41.8%, respectively. The average methane content in biogas was about 66% for all reactors.
"The residue after these operations is the hydromechanically separated organic fraction of municipal solid wastes, suitable for biogas production . However, due to generally lower organic matter and nutrient contents, the organic fraction of municipal solid waste derived from mechanical sorting gives a lower biogas yield compared to the production of biogas from source sorted OFMSW (Bolzonella et al., 2006; Dong et al., 2010). In the previous research, it was demonstrated that biogas production from hydromechanically separated OFMSW can be significantly enhanced when the wastes are co-digested with municipal sewage sludge which is also regarded as a substrate giving moderate to low biogas yields (Borowski, 2015). "
[Show abstract][Hide abstract] ABSTRACT: This paper examines the temperature-phased anaerobic digestion (TPAD) process treating the mixture of municipal sewage sludge with the hydromechanically separated organic fraction of municipal solid waste (HS-OFMSW). The experiments showed that the performance of the TPAD process strongly depends on the conditions applied in the thermophilic stage. The TPAD system operated at a solids retention time (SRT) of 1 and 14 days in the first and second steps, respectively, achieved the overall methane yield of 333 l CH4 kgVS−1 and the volatile solids reduction of 52.1%, whereas the corresponding values reported for a control single-stage mesophilic process were 230 l CH4 kgVS−1 and 37.23%, respectively. However, when an SRT of the thermophilic reactor was extended to 2 days, the methane production in the subsequent mesophilic stage significantly decreased. It was therefore concluded that the prolonged exposure of feedstock to the thermophilic temperatures can lead to greater intensity of protein degradation. Consequently, higher amounts of ammonia are liberated to the liquid phase, which results in the inhibition of methanogenesis in the subsequent mesophilic step. Moreover, ammonia affects the release and distribution of volatile fatty acids, which also influences the performance of the whole TPAD system.
"indicates a nonlinear relationship between the TS content and the initial methane production rate. This behaviour is not in agreement with the linear relationship between the two parameters found by several other authors with different organic substrates      "
[Show abstract][Hide abstract] ABSTRACT: This work investigates the start-up phase of anaerobic digestion in wet, semidry and dry conditions of rice straw analysing the role of volatile fatty acid (VFA) production on process kinetics. Methane production yields and biodegradation kinetics in reactors operated under wet semi-dry and dry conditions were investigated. The experimental results showed a reduction of the specific final methane production yield of 57% and 63% in, respectively, semi-dry (TS = 14.8%) and dry (TS = 23.4%) conditions compared to wet (TS = 4.8%) conditions. The total VFA concentration and speciation are proposed as indicators of process development at different total solids content. High VFA concentrations were found in dry conditions, with a maximum total VFA concentration of 2110 mg/kg in dry condition, 930 mg/kg in semi-dry conditions and 180 mg/kg in wet conditions.
"Biogas fermentation processes are classified into wet fermentations (TS concentration less than 10%) (Deng et al., 2014), semi-dry fermentations (TS concentration ranging from 10% to 20%) (Bolzonella et al., 2003; Dong et al., 2010), and dry fermentations (TS concentration more than 20%) (Abouelenien et al., 2009; Kusch et al., 2008) . Dry fermentation has attracted increasingly extensive attentions in the studies of biogas fermentation with advantages of water-saving, convenient operation, high yields, high fermentation slurry concentration, and better energyrecovery (Fdez-Güelfo et al., 2010; Kafle and Kim, 2013; Yabu et al., 2011). "
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