Effects of biochar combined with MgO desulfurization waste residue on nitrogen conversion and odor emission in chicken manure composting

Aim: Chicken manure is known to produce strong odors during aerobic composting, which not only pollutes the surrounding environment but also leads to the loss of valuable nutrients like nitrogen and sulfur, thus reducing the quality of the fertilizer. Methods: In this study, we explored the use of biochar combined with MgO desulfurization waste residue (MDWR) as a novel composting additive. Our approach involved conducting composting tests, characterizing the compost samples, conducting pot experiments, and examining the impact of the additives on nitrogen retention, deodorization, and compost quality. Results: Our findings revealed that the addition of biochar and MDWR significantly reduced ammonia volatilization in chicken manure compost, demonstrating a reduction rate of up to 60.12%. Additionally, the emission of volatile organic compounds (VOCs) from chicken manure compost treated with biochar and MDWR decreased by 44.63% compared to the control group. Conclusions: The composting product treated with both biochar and MDWR (CMB) exhibited a 67.7% increase in total nitrogen (TN) compared to the blank control group, surpassing the other treatment groups and showcasing the synergistic effect of these two additives on nitrogen retention. Moreover, the CMB treatment facilitated the formation of struvite crystals. Furthermore, our pot experiment results demonstrated that the CMB treatment enhanced vegetable yield and quality while reducing nitrate content. These findings highlight the significant impact of MDWR on nitrogen retention, deodorization, and compost quality enhancement, thereby indicating its promising application prospects.

Regulating method of microbial driving the phosphorus bioavailability in factory composting

Phosphorus bioavailability is essential for assessing compost quality. However, the effects of microbial and environmental factors on potentially active phosphorus (H2O-P + NaHCO3-Pi) in factory compost have not been investigated. The findings indicated that chicken manure had significantly higher available phosphorus (AP) and H2O-P + NaHCO3-Pi throughout the composting process than kitchen waste (P < 0.05). Chicken manure compost also exhibited higher α-microbial diversity. Novibacillus, Marinococcaceae and Bacillales were the core bacteria involved in bioavailable phosphorus conversion in both composts. The core bacteria in kitchen waste compost had a broader range of phosphorus metabolism functions. Moreover, moisture and pH were the key environmental factors that significantly influenced the bioavailable phosphorus (P < 0.05). These findings provide a scientific foundation for regulating the composting process and improving phosphorus utilization efficiency.

Regulatory effects of different anionic surfactants on the transformation of heavy metal fractions and reduction of heavy metal resistance genes in chicken manure compost

Surfactants are widely used as a passivating agent in heavy metal passivation process, but their effect on transformation of heavy metal fraction and reduction of heavy metal resistance genes (MRGs) in composting process is still unknown. The aim of this study was to compare the effects of two anionic surfactants (rhamnolipid and sodium dodecyl sulfate) on heavy metal passivation and resistance gene reduction in chicken manure composting. The results showed that the addition of surfactant can effectively enhance degradation of organic matter (OM). Both surfactants could effectively reduce the bioavailability of heavy metals (HMs) and the relative abundance of resistance genes, especially rhamnolipids. The potential functional bacteria affecting heavy metal passivation were identified by the changes of microbial community. Redundancy analysis (RDA) showed that protease (PRT) activity was the key factor affecting the fractions of the second group of HMs including ZnF1, CuF1, CuF2, PbF1 and PbF3. These findings indicate that addition of anionic surfactants can reduce the bioavailability of HMs and the abundance of resistance genes in compost products, which is of guiding significance for the reduction of health risks in the harmless utilization of livestock and poultry manure.

Effect of biochar combined with a biotrickling filter on deodorization, nitrogen retention, and microbial community succession during chicken manure composting

The high-nitrogen content and dense structure of poultry manure compost cause volatilization of N to ammonia (NH₃). This study evaluated the combined application of biochar and biotrickling filtration (BTF) to remove of odor in chicken manure mixed straw compost (w/w, 2.5:1). Adding of 10% biochar reduced NH₃, hydrogen sulfide (H₂S), and total volatile organic compounds (TVOCs) contents by 20.04%, 16.18%, and 17.55% respectively, and decreased the N loss rate by 8.27%, compared with those observed in control. The organic matter content decreased by 28.11% and germination index reached 97.36% in the experimental group. Meanwhile, the N-cycling microorganisms such as Pusillimonas and Pseudomonas became more active, and the relative abundance of sulfur-cycling microorganisms Hydrogenispora decreased in the experimental group. Following BTF application, the NH₃, H₂S, and TVOCs removal rates reached 95%, 97%, and 53%, respectively.

Effects of two different organic amendments addition to soil on sorption-desorption, leaching, bioavailability of penconazole and the growth of wheat (Triticum aestivum L.)

This study investigated the effects of sugarcane bagasse compost (SBC) and chicken manure compost (CMC) on the sorption-desorption, leaching and bioavailability of the fungicide penconazole in soil in a laboratory setting. The autoclave-treated SBC or CMC was applied at 2.5% and 5.0% (w/w). Results of batch equilibrium experiments exhibited that the sorption capacity of soils for penconazole was significantly promoted by the addition of SBC or CMC, whereas desorption of penconazole was drastically reduced; the influence was enhanced as the amount of organic amendments increased. Results of column leaching experiment indicated that the addition of SBC or CMC significantly limited the vertical movement of penconazole through the soil columns, considerably decreasing the content of penconazole in the soil leachate. Furthermore, results of bioavailability experiments demonstrated that the addition of organic amendments (SBC or CMC) remarkably influenced the uptake and translocation of penconazole, decreased penconazole accumulation in the plant tissues and increased the plant elongation and biomass. These data revealed important changes in pesticide behavior under SBC or CMC application, which should be useful for developing strategies to protect groundwater and crops from contamination from the residual pesticides in soil.