106 / 2023-07-19 22:02:02

Impacts of Biochar and Fe2O3 in Enhancing Humification and Mitigating Cu and Zn Bioavailability in Co-composting of Pig Manure and Wine Grape Pomace

Composting; Biochar, Fe2O3; Wine grape pomace; Humic acid; Cu and Zn

This comprehensive research delineates the unique roles of biochar and Fe₂O₃ in the co-composting of pig manure and wine grape pomace, emphasizing their impacts on humification and heavy metal passivation, notably copper (Cu) and zinc (Zn). While Fe₂O₃ significantly enhanced microbial symbiotic interactions and humic acid (HA) yield, it was biochar that augmented microbial diversity. The combined application of these two agents, however, was found to curtail the humification process. Additionally, temperature, pH, Bacillus and Actinomadura were identified as central determinants influencing the HA content. In terms of heavy metal passivation, biochar outperformed Fe₂O₃ by achieving a peak passivation rate of 52.0% for Cu and 20.4% for Zn, as opposed to Fe₂O₃'s 39.8% for Cu and 14.7% for Zn. However, when both were used together, Cu and Zn passivation reached rates of 31.1% and 17.6%, respectively. Biochar-enriched compost demonstrated an elevated presence of carboxylic and phenolic hydroxyl groups in humic acid, compared to that with Fe₂O₃. The findings also underline the positive influence of dominant microbial genera such as Pseudomonas and Corynebacterium, along with certain microbial metabolic activities, on Zn passivation. The findings contribute to an improved understanding of the roles of biochar and Fe₂O₃ in composting processes, and they offer guidance for optimizing Cu/Zn passivation pathways in pig manure composting.