Monitoring of seven industrial anaerobic digesters supplied with biochar

Abstract

Background Recent research articles indicate that direct interspecies electron transfer (DIET) is an alternative metabolic route for methanogenic archaea that improves microbial methane productivity. It has been shown that multiple conductive materials such as biochar can be supplemented to anaerobic digesters to increase the rate of DIET. However, the industrial applicability, as well as the impact of such supplements on taxonomic profiles, has not been sufficiently assessed to date. Results Seven industrial biogas plants were upgraded with a shock charge of 1.8 kg biochar per ton of reactor content and then 1.8 kg per ton were added to the substrate for one year. A joint analysis for all seven systems showed a decreasing trend for the concentration of acetic acid (p < 0.0001), propionic acid (p < 0.0001) and butyric acid (p = 0.0022), which was significant in all cases. Quantification of the cofactor F420 using fluorescence microscopy showed a reduction in methanogenic archaea by up to a power of ten. Methanogenic archaea could grow within the biochar, even if the number of cells was 4 times less than in the surrounding sludge. 16S-rRNA gene amplicon sequencing showed a higher microbial diversity in the biochar particles than in the sludge, as well as an accumulation of secondary fermenters and halotolerant bacteria. Taxonomic profiles indicate microbial electroactivity, and show the frequent occurrence of Methanoculleus, which has not been described in this context before. Conclusions Our results shed light on the interplay between biochar particles and microbial communities in anaerobic digesters. Both the microbial diversity and the absolute frequency of the microorganisms involved were significantly changed between sludge samples and biochar particles. This is particularly important against the background of microbial process monitoring. In addition, it could be shown that biochar is suitable for reducing the content of inhibitory, volatile acids on an industrial scale.

The role of biochar on alleviating ammonia toxicity in anaerobic digestion of nitrogen-rich wastes: A review

“…Therefore, future research should focus on supplementing microbiology consortium with mutual relationships. Heitkamp et al (2021) found that the concentration of microorganisms attached to biochar was higher than the average concentration of suspended and attached growth microorganisms. This means that biochar can be used as a carrier for microorganisms to alleviate ammonia inhibition and is an ideal partner for bioaugmentation.…”

Syngas Fermentation to Acetate and Ethanol with Adaptative Electroactive Carboxydotrophs in Single Chambered Microbial Electrochemical System

“…Lower Simpson (2.5) and Shannon (0.6) index values were observed in the enriched culture, evidenced by the distributions of the selected community dominance that drives the specific metabolic reactions. Low variance and evenness distributions of the carboxydotrophic microbes account for the specific acetogenic and solventogenic process in which syngas feedstock converted into the WLP pathway metabolites account for the microbiome assisting the dominant growth of the specific microbiome (C1-fixing) [ 43 ]. Cho1 and abundance-based coverage estimators (ACE) species richness was depicted in the median of 530 and 480, respectively.…”

Intervention Strategies for the “Inhibited Steady State” Dry Thermophilic Anaerobic Digesters: The Mitigation Mechanisms of Tailored Biochar

“…Thus, a relative accumulation was still observed in the upstream substances’ (propionic acid, butyric acid) concentration under high ammonia concentration. Furthermore, the pH of all reactors varied within a narrow range from 8.4 to 8.9 (Figure S2), which is the range in which most actual AD plants operate and is an appropriate range for methanogen growth. , The reason for the comparatively stable pH is the synchronous change in TAN, which has the function of buffering and neutralizing the acid. However, the stability in this case is not synonymous with reaching sufficiently good performance.…”

“…Furthermore, the biochar addition method reported by existing studies still primarily started from the initiation of fermentation rather than being targeted at the stage of a failed methanization, making it difficult to identify whether it can be regarded as an antidote for emergency intervention to alleviate the inhibited steady state. Although there have been a few studies exploring the application of biochar in a full-scale plant or in a failed digester, both focused on the single acid stress and planktonic microorganisms existing in the digesters, leading to the primary functional microorganisms potentially promoted by the added biochar still remaining elusive. Moreover, existing studies relating to biochar-associated biofilms merely focused on microbial diversity instead of the amount of microorganisms …”