Effects of rice straw biochar on methanogenic bacteria and metabolic function in anaerobic digestion

Abstract

Anaerobic digestion technology mitigates agricultural organic waste pollution, thereby alleviating the energy crisis. Biochar materials increase the utilisation rate of biomass resources and promote the enrichment and growth of microorganisms. Biochar is an effective exogenous additive that stabilises the anaerobic digestion, improves anaerobic digestion efficiency and gas production. Herein, biochar materials were prepared from rice straw utilising the sequencing batch anaerobic digestion process. The biochar microstructure was characterised by scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET) analysis, and microbial succession and metabolic pathways were analysed using 16S rRNA sequencing to reveal the molecular mechanisms. Rice straw biochar addition increased gas production during anaerobic fermentation. SEM revealed that numerous cocci and microbacteria became agglomerated and attached to the surface and pores of biochar, which was revealed by BET analysis to be a good habitat for microorganisms. After anaerobic digestion, the specific surface area and total pore volume of biochar decreased. 16S rRNA gene sequencing showed that biochar affected the abundance of certain bacteria and archaea. Biochar had no obvious effect on the function of bacterial flora but inhibited carbohydrate metabolism by bacteria and glycan biosynthesis and metabolism by archaea in the anaerobic fermentation system while promoting lipid metabolism by archaea. Biochar addition inhibited acetic acid production in the anaerobic fermentation system and promoted methane production based on hydrogen and carbon dioxide levels.

Anaerobic Digestion of Brewer’s Spent Grain With Biochar – Biogas Production Kinetics and Process Efficiency

“…That is opposite to the findings of (S. Wang et al, 2022), that added straw biochar (600°C for 20 min) at 7.1 g BC ×L -1 to the AD of cow dung. (S. Wang et al, 2022) also obtained methane production enhancement after biochar addition but this effect was due to an increase of hydrogenotrophic methanogens abundance, while acetoclastic methanogens such as Methanosaeta decreased massively (S. Wang et al, 2022). On the contrary results of (Masebinu et al, 2021) showed that for a well-working AD system without any severe disturbances, biochar does not improve methane production nor decrease it and microbial community composition is not altered.…”

“…Interestingly BC addition increased the abundance of acetoclastic methanogens that convert acetate (CH 3 COOH) to methane and carbon dioxide, while reducing the abundance of hydrogenotrophic methanogens that produce methane from hydrogen and CO 2 (Zhang et al, 2019). That is opposite to the findings of (S. Wang et al, 2022), that added straw biochar (600°C for 20 min) at 7.1 g BC ×L -1 to the AD of cow dung. (S. Wang et al, 2022) also obtained methane production enhancement after biochar addition but this effect was due to an increase of hydrogenotrophic methanogens abundance, while acetoclastic methanogens such as Methanosaeta decreased massively (S. Wang et al, 2022).…”

Advances, trends and challenges in the use of biochar as an improvement strategy in the anaerobic digestion of organic waste: a systematic analysis

“…It is important to highlight the connection between these issues, since the physicochemical and functional properties depend directly on optimizing the generation of value-added by-products obtained by applying AD. [ 11 , 41 , 63 , 64 ] The third subgroup is made up of the terms ‘co-digestion’ and ‘digestate’ and the fourth subgroup is made up of the word ‘sludge.’ As the groupings are smaller, they indicate that they are the areas where the application of BC is being explored, with co-AD being one of the most studied topics ( Figure 4 ).…”

Production of biochar from crop residues and its application for anaerobic digestion

“…Furthermore, based on the ash composition in biochar, putting it an anerobic digester can enhance the concentration of trace metals and alkalis, resulting in improved performance of the process (Pan et al, 2019b). Biochar's porous structure and surface area serves as a living environment for microorganisms (Wang et al, 2022). However, heating rate, reaction temperature, and feedstock all affect biochar characteristics, including the fixed carbon content, nutrient content and availability, cation exchange capabilities and pH (Ghodake et al, 2021).…”