The effect of mixt. interactions, i.e., synergy and antagonism, previously obsd. in batch operation mode were evaluated under semi-continuous co-digestion of slaughterhouse waste (SB) and its different combinations with manure (M), various crops (VC), and municipal solid waste (MSW). The effects on the process performance and the microbial community structure were studied. The digestion of SB failed at an OLR of 0.9 g VS/L-day. However, stable performance with higher loadings was obsd. for mixts. that displayed synergy obtained earlier in the batch mode (i.e., SB + M, SB + VC + MSW). Bacterial and Archaeal groups increased for the SB + M and SB + VC + MSW, compared with the digestion of SB alone and that for SB + VC. The combination that showed antagonistic effects (SB + VC) resulted in unstable operation and poor representation of methanogens. It was proved that synergetic or antagonistic effects obsd. in batch mode due to the different mixt. compns. could be correlated to process performance, as well as the development of the microbial community structure during semi-continuous operation. [on SciFinder(R)]

Different mixture ratios of solid cattle slaughterhouse wastes (SB), manure (M), various crops (VC), and municipal solid wastes (MSW) were investigated for biogas production. The objective was to explore possible significant synergistic effects obtained from the combination of these different substrates. The performance of the process was assessed in thermophilic anaerobic batch co-digestion assays, using a four factor mixture design and methane yield (Y-CH4) and specific methane production rate (r(scH4)) as response variables. The highest methane yield, 655 NmL CH4/g VS was obtained when equal parts (ww) of SB, M, VC, and MSW were combined, while the combination of SB, M, and MSW resulted in the highest specific methane production rate (43 NmL CH4/g VS/d). A mixture design model was fitted to data in order to appraise synergistic and antagonistic interactions. Mixing all four substrates resulted in a 31% increase of the expected yield which was calculated from the methane potential of the individual fractions, clearly demonstrating a synergistic effect due to more balanced nutrient composition enhancing the anaerobic digestion process. However, no significant antagonistic effects were observed. In order to maximize both response variables simultaneously, a response surface method was employed to establish the optimal combination of substrate mixtures. The statistical results and analysis of the biological process gave a coherent picture of the results. (C) 2014 Elsevier B.V. All rights reserved.