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Anaerobic digestion processes were compared in multiple reactors using glucose and starch as substrates. For reproducibility studies, five reactors were run in parallel as consecutive 7d-batches and supplied with increasing amounts of starch (2 to 13 g L−1). For concentrations < 10 g L−1, production of biogas and organic acids as well as the population structure changed but remained similar, while populations split and statistically significant differences in metabolic intermediate concentration and biogas composition/volume were observed at higher starch concentrations. Based on this reproducibility study, the influence of sludge volume and mixing intensity were investigated using reactors with working volumes of 0.75 L and 1.5 L, with and without mechanical mixing. Mixing positively influenced reaction rates at lower substrate concentrations (up to 4 g L−1), while a negative influence on the process stability was observed at higher concentrations. In general, the larger reactors showed better productivities and stabilities than the corresponding smaller ones.​

The full text can be found at https://doi.org/10.1016/j.biteb.2020.100444.