Comparison of the basic processes of aerobic, anaerobic, and aerobic-anaerobic coupling composting of Chinese medicinal herbal residues

Enhancing simultaneous nitrogen and phosphorus availability through biochar addition during Chinese medicinal herbal residues composting: Synergism of microbes and humus

The disposal of Chinese medicinal herbal residues (CMHRs) derived from Chinese medicine extraction poses a significant environmental challenge. Aerobic composting presents a sustainable treatment method, yet optimizing nutrient conversion remains a critical concern. This study investigated the effect and mechanism of biochar addition on nitrogen and phosphorus transformation to enhance the efficacy and quality of compost products. The findings reveal that incorporating biochar considerably enhanced the process of nutrient conversion. Specifically, biochar addition promoted the retention of bioavailable organic nitrogen and reduced nitrogen loss by 28.1 %. Meanwhile, adding biochar inhibited the conversion of available phosphorus to non-available phosphorus while enhancing its conversion to moderately available phosphorus, thereby preserving phosphorus availability post-composting. Furthermore, the inclusion of biochar altered microbial community structure and fostered organic matter retention and humus formation, ultimately affecting the modification of nitrogen and phosphorus forms. Structural equation modeling revealed that microbial community had a more pronounced impact on bioavailable organic nitrogen, while humic acid exerted a more significant effect on phosphorus availability. This research provides a viable approach and foundation for regulating the levels of nitrogen and phosphorus nutrients during composting, serving as a valuable reference for the development of sustainable utilization technologies pertaining to CMHRs.

Synergistic improvement of humus formation in compost residue by fenton-like and effective microorganism composite agents

Improving the humification of compost through a synergistic approach of biotic and abiotic methods is of great significance. This study employed a composite reagent, comprising Fenton-like agents and effective microorganisms (EM) to improve humification. This composite reagent increased humic-acid production by 37.44 %, reaching 39.82 g kg-1, surpassing the control group. The composite reagent synergistically promoted micromolecular fulvic acid and large humic acid production. Collaborative mechanism suggests that Fenton-like agents contributed to bulk residue decomposition and stimulated the evolution of microbial communities, whereas EMs promoted highly aromatic substance synthesis and adjusted the microbial community structure. Sequencing analysis indicates the Fenton-like agent initiated compost decomposition by Firmicutes, and EM reduced the abundance of Virgibacillus, Lentibacillus, and Alcanivorax. Applied as an organic fertilizer in Brassica chinensis L. plantations, the composite reagent considerably improved growth and photosynthetic pigment content. This composite reagent with biotic and abiotic components provides a learnable method for promoting humification.

Effects of adding steel slag on humification and characteristics of bacterial community during phosphate-amended composting of municipal sludge

This study aimed to investigate the effects of different proportions (0%, 5%, 7.5%, and 10%) of steel slag (SS) on humification and bacterial community characteristics during phosphate-amended composting of municipal sludge. Compared with adding KH2PO4 alone, co-adding SS significantly promoted the temperature, pH, nitrification, and critical enzyme activities (polyphenol oxidase, cellulase, laccase); especially organic matter (OM) degradation rate (25.5%) and humification degree (1.8) were highest in the 5%-SS treatment. Excitation-emission matrix-parallel factor confirmed that co-adding SS could promote the conversion of protein-like substances or microbial by-products into humic-like substances. Furthermore, adding 5%-SS significantly improved the relative abundances of Actinobacteria, Firmicutes and the genes related to carbohydrate and amino acid metabolism, and enhanced the interactions of bacterial community in stability and complexity. The partial least squares path model indicated that OM was the primary factor affecting humification. These results provided a promising strategy to optimize composting of municipal sludge via SS.

Analysis of microbial communities in solid and liquid pig manure during the fertilization process

Utilizing livestock manure as organic fertilizer in sustainable agriculture is crucial and should be developed through an appropriate manufacturing process. Solid-liquid separation contributes to reducing odor, managing nutrients in livestock excretions, and lowering the cost of transporting manure to arable soil. To investigate the impact of fermentation after solid-liquid separation, we examined the specific correlation between chemical properties and bacterial communities in solid-liquid manures before and after the fermentation process. In terms of chemical properties before fermentation, the levels of electrical conductivity, nitrogen, ammonium nitrogen (NH4+-N), potassium, sodium, and chloride were higher in the liquid sample than in the solid sample. However, the chemical components of the liquid sample decreased during fermentation, which could be attributed to the low organic matter content. Many chemical components increased in the solid samples during fermentation. Fifty-six bacterial species were significantly correlated with NH4+-N and phosphorus. Following fermentation, their abundance increased in the solid samples and decreased in the liquid samples, indicating the potential for NH4+-N release or phosphorus mineralization from organic matter. These results provide information regarding changes in nutrient and bacterial formation when applying the fermentation process after solid-liquid separation.

Effects of biochar and volcanic rock addition on humification and microbial community during aerobic composting of cow manure

Additives are important for accelerating humification during aerobic composting. The impacts of porous additives biochar and volcanic rock on the physicochemical parameters, maturity indicators, microbial communities, and bacterial functional metabolism during the aerobic composting of cow manure were investigated in this study. The results showed that the biochar addition decreased the E4/E6 value by 10.42% and increased the abundance of Geobacillus (1.69 times), and volcanic rock addition decreased the E4/E6 value by 11.31% and increased the abundance of Thermobacillus (1.29 times) and Paenibacillus (1.72 times). The network analysis demonstrated that biochar promoted maturity by reducing the abundance of Pseudomonas and increasing the abundance of genes related to the metabolism of other amino acids, while volcanic rock promoted maturity by reducing the abundance of genes related to nucleotide metabolism. These results provided data and theoretical justification for the selection of porous additives for composting.

Product maturation and antibiotic resistance genes enrichment in food waste digestate and Chinese medicinal herbal residues co-composting

The land application of food waste digestate (FWD) requires a composting process to improve its soil amendment performance and alleviate environmental risks. This study proposed co-composting of Chinese medicinal herbal residues (CMHRs) and FWD as a means to improve the maturation performance and investigated the evolution of antibiotic resistance genes (ARGs). Results demonstrated that CMHRs addition effectively accelerated the maturity of FWD composting to less than 35 days, remarkably removed its remaining antibiotics by 83.0% and promoted the formation of humification substances. However, both quantitative PCR and 16S rRNA sequencing analysis indicated that a significant enrichment of ARGs and mobile genetic elements including frA1, tetX, blaTEM, InuB-01, aadA2-02 and IntI-1 was observed via the co-composting of FWD and CMHRs. These results indicated that the land application of products obtained from FWD and CMHRs co-composting is at risk of spreading ARGs, although the composting process could be significantly improved.

Effect of Tea Seed Oil on In Vitro Rumen Fermentation, Nutrient Degradability, and Microbial Profile in Water Buffalo

Tea seed oil (TSO) was investigated for its effects on rumen fermentation and in vitro parameters of bacterial communities in water buffalo diets containing Siraitia grosvenorii and soybean residues. TSO was added at rates of 0% (control group (CT)), 0.5% (T1), 1% (T2), and 2% (T3) of the in vitro fermentation substrate weight (dry matter (DM) basis). T2 and T3 had significantly lower acetate and total volatile fatty acid contents but a significantly higher microbial crude protein content than CT. The lowest NH3-N content was observed in T1 and T2. Treatment significantly increased DM digestibility, with the highest percentage observed in T2. T2 showed significantly higher crude protein digestibility than CT. TSO supplementation significantly increased the C18:2n6c, C18:2 trans-10, cis-12, and C20:4n6 concentrations compared to those in CT. The total number of bacteria was significantly lower in T2 than in CT. TSO supplementation decreased the total bacteria, fungi, and methanogen populations but increased rumen microorganism diversity and richness. In conclusion, TSO can regulate the number and flora of rumen microorganisms through antimicrobial activity, thereby affecting rumen fermentation patterns, reducing methane production, and improving nutrient digestibility, and an optimal supplementation rate appears to be achieved with 1% TSO (DM basis).