Biochar-based solid acid accelerated carbon conversion by increasing the abundance of thermophilic bacteria in the cow manure composting process

Potential of novel iron 1,3,5-benzene tricarboxylate loaded on biochar to reduce ammonia and nitrous oxide emissions and its associated biological mechanism during composting

In this study, a novel iron 1,3,5-benzene tricarboxylate loaded on biochar (BC-FeBTC) was developed and applied to kitchen waste composting. The results demonstrated that the emissions of NH3 and N2O were significantly reduced by 57.2% and 37.8%, respectively, compared with those in control group (CK). Microbiological analysis indicated that BC-FeBTC addition altered the diversity and abundance of community structure as well as key functional genes. The nitrification genes of ammonia-oxidizing bacteria were enhanced, thereby promoting nitrification and reducing the emission of NH3. The typical denitrifying bacterium, Pseudomonas, and critical functional genes (nirS, nirK, and nosZ) were significantly inhibited, contributing to reduced N2O emissions. Network analysis further revealed the important influence of BC-FeBTC in nitrogen transformation driven by functional microbes. These findings offer crucial scientific foundation and guidance for the application of novel materials aimed at mitigating nitrogen loss and environmental pollution during composting.

Biochar addition accelerates the humification process by affecting the microbial community during human excreta composting

Biochar addition plays an important role in manure composting, but its driving mechanism on microbial succession and humification process of human excreta composting is still unclear. In the present study, the mechanism of biochar addition was explored by analysing the humification process and microbial succession pattern of human excreta aerobic composting without and with 10% biochar (HF and BHF). Results indicated that BHF improved composting temperature, advanced the thermophilic phase by 1 d, increased the germination index by 49.03%, promoted the growth rate of humic acid content by 17.46%, and raised the compost product with the ratio of humic acid to fulvic acid (HA/FA) by 16.19%. Biochar regulated the diversity of fungi and bacteria, increasing the relative abundance of Planifilum, Meyerozyma and Melanocarpus in the thermophilic phase, and Saccharomonospora, Flavobacterium, Thermomyces and Remersonia in the mature phase, which accelerates the humification. Bacterial communities' succession had an obvious correlation with the total carbon, total nitrogen, and temperature (P < 0.05), while the succession of fungal communities was influenced by the HA/FA and pH (P < 0.05). This study could provide a reference for the improvement of on-site human excreta harmless by extending the thermophilic phase, and facilitating the humification in human excreta compost with biochar addition.

Bacterial community dynamics and co-occurrence network patterns during different stages of biochar-driven composting

Bacterial communities were dynamically tracked at four stages of biochar-driven sheep manure pile composting, and the co-occurrence networks with keystone taxa were established. The succession of bacterial community obvious varied during the composting process, Proteobacteria predominant in initial stage (39%) then shifted into Firmicutes in thermophilic (41%) and mesophilic (27%) stages, finally the maturation stage dominant by Bacteroidota (26%). Visualizations of bacterial co-occurrence networks demonstrate more cooperative mutualism and complex interactions in the thermophilic and mesophilic phases. Noticeably, the 7.5 and 10% biochar amended composts shown highest connections (736 and 663 total links) and positive cooperation (97.37 and 97.13% positive link) as well as higher closeness centrality and betweenness centrality of keystone taxa. Overall, appropriate biochar addition alters bacterial community succession and strengthens connection between keystone taxa and other bacteria, with 7.5 and 10% biochar amended composts has intense mutualistic symbiosis among bacterial communities.

Biochar assists phosphate solubilizing bacteria to resist combined Pb and Cd stress by promoting acid secretion and extracellular electron transfer

Microorganisms have difficulty surviving and performing remediation functions in mixed systems with high concentrations of Pb and Cd. Biochar has the potential to assist microorganism remediation as an excellent adsorbent for heavy metals. In this study, pig manure biochar (PMB) was used to assist phosphorus solubilizing bacteria (PSB) to explore the mineralization protection and biofeedback mechanism of biochar on PSB under mixed stress of 1000 mg/L Pb²⁺ and 500 mg/L Cd²⁺. The adsorption results showed that the removal of Pb²⁺ and Cd²⁺ by PMB+PSB was 148.77% and 72.27% higher than that by PSB. Meanwhile, the non-bioavailable fraction of Cd²⁺ and acid-soluble fraction of Pb²⁺ in PMB+PSB were increased by 9% and 3%, respectively. Mineralogical and microbial secretion results confirm that showed that the acidic soluble fraction and non-bioavailable fraction were mostly Pb/Cd-carbonate and Pb/Cd-phosphate. The pore adsorption and precipitation (carbonate) of biochar were able to reduce the exposure of PSB to Pb/Cd and the background stress concentration, thus stimulating the biological positive feedback effect of PSB and forming a microenvironment in the cell periphery. The vesicle detoxification and extracellular polymeric substance protection mechanism of PSB were improved under biochar protection, and the individual size and activity of PSB cells were enhanced. Besides, citric acid release from PSB (28.85% increase) accelerated the dissolution of unstable Cd-carbonate, thereby releasing a large amount of Cd²⁺ to compete with Pb²⁺ for PO₄^3-. Thus, the protection of biochar and the positive feedback effect of PSB could reduce the biotoxicity of Cd²⁺ in the stress system by preferentially forming a stable Cd-phosphate. In addition, the excellent electrical conductivity and organic material adsorption of biochar increased the extracellular electron transport rate of microorganisms, which further accelerated the mineralization and immobilization of Pb²⁺ and Cd²⁺, so as to ensure the repair effect of PSB on heavy metals.

Performances of antibiotic resistance genes profile upon the action of biochar-activated peroxydisulfate in composting

In this study, the amendment of biochar-activated peroxydisulfate during composting to remove antibiotic resistance genes (ARGs) by direct (microbial community succession) and indirect methods (physicochemical factors) was analyzed. When implementing indirect methods, the synergistic effect of peroxydisulfate with biochar optimized the physicochemical habitat of compost, maintaining its moisture within a range of 62.95%-65.71%, and a pH of 6.87-7.73, and causing the compost to mature 18 days earlier than the control groups. The direct methods caused the optimized physicochemical habitat to adjust the microbial communities and reduce the abundance of most of the ARG host bacteria (Thermopolyspora, Thermobifida, and Saccharomonospora), thus inhibiting this substance's amplification. Heatmap analysis confirmed the necessary connection between physicochemical factors, microbial communities, and ARGs. Moreover, a mantel test confirmed the direct significant effect of the microbial communities on ARGs and the indirect significant effect of physicochemical factors on ARGs. The results showed that the abundance of more ARGs was down-regulated at the end of composting and regulated by biochar-activated peroxydisulfate, especially for the abundance of AbaF, tet(44), golS, and mryA, which was significantly decreased by 0.87-1.07 fold. These results provide new insights into the removal of ARGs during composting.

Aerobic composting of chicken manure with amoxicillin: Alpha diversity is closely related to lipid metabolism, and two-component systems mediating their relationship

Composting is a technology that can use various functional microorganisms to degrade antibiotics. However, antibiotics will cause a coercion for the growth of most microorganisms. Microorganism can survive different environments, thanks to the development of different adaptive responses. Often, two-component systems sense changes in the environment and trigger a cellular response and adaptation. Therefore, the main purpose of this study was to explore how the two-component system modulates the corresponding metabolic functions to affect alpha diversity during composting. The results show that amoxicillin increases species diversity, reduces species richness. Lipid metabolism is an important metabolic pathway mediating changes in alpha diversity. Two-component system indirectly affects alpha diversity by regulating lipid metabolism. Firmicutes are important microbial communities mediating changes in alpha diversity This work presents an understanding of the impact of environmental information processing on microbial diversity, during composting.