Stirring and biomass starter influences the anaerobic digestion of different substrates for biogas production

Abstract

Here, we present the results of lab‐scale experiments conducted in a batch mode to determine the biogas yield of lipid‐rich waste and corn silage under the effect of stirring. Further semi‐continuous experiments were carried out for the lipid‐rich waste with/without stirring. Additionally, it was analyzed how the starter used for the batch experiment influences the digestion process. The results showed a significant stirring effect on the anaerobic digestion only when seed sludge from a biogas plant was used as a starter. In this case, the experiments without stirring yielded only about 50% of the expected biogas for the investigated substrates. The addition of manure slurry to the batch reactor as part of the starter improved the biogas production. The more diluted media in the reactor allowed a better contact between the bacteria and the substrates making stirring not necessary.

Floating layer formation, foaming, and microbial community structure change in full-scale biogas plant due to disruption of mixing and substrate overloading

“…It is probable that the increased concentrations of VFA in the methanogenic reactors were mainly caused by higher VFA concentrations in the fed substrate combined with an insufficient distribution of the substrate due to the stirring disturbances. Rojas et al [33] revealed a decreasing performance of the biogas process in a reactor without stirring and related it to the insufficient contact between substrate and microorganisms. After restart of the agitator in month 5, the VFA concentrations in the two methanogenic reactors remained on a low level although the VFA concentrations in the hydrolytic stage increased again to more than 24,000 mg L −1…”

Assessment of Economical Biogas Production From Chilean Municipal Solid Waste in a Decentralized Off-Grid Strategy

“…An appropriate agitation technology is essential since stirring has a crucial influence on the microbial community structure and the SBY. Thus, it has been highlighted by previous authors a SBY reduction between 30 % to 40 % when the digestate is unmixed (Rusin et al, 2017;Rojas et al, 2010).…”

Effect of Lactate and Starter Inoculum on Biogas Production from Fresh Maize and Maize Silage

“…The structure and activity of the microbial community involved in fermenta-tion often depends on the original inoculum source and starter biomass, as well as the operational and environmental conditions [19] [20] [21] [22]. Bacterial communities in biogas plants adapt to the substrates fed [23].…”

“…Such contradictions could possibly be due to the different nature and microbial composition of the inoculum. Numerous studies show that the microbial communities and their behavior in biogas reactors are controlled mainly by the starter inocula [20] [24] [37] [38]. Due to the importance of starter inoculum on the system, using silage as a primary substrate may have varying results in biogas production, as this is dependent whether the microbial community is adapted to lactic acid or not.…”