Improving composting quality and optimizing bacterial community: A study on the effects of bamboo sphere, vermiculite, and sponge iron in cattle manure composting

Abstract

Composting represents a widely adopted approach for managing cattle manure, yet conventional approaches often suffer from inefficient decomposition rates and suboptimal product quality. This study systematically investigated the optimization of aerobic composting processes using cattle manure and rice straw as primary substrates, supplemented with three distinct additives: hollow bamboo spheres, vermiculite, and sponge iron. Through integrated monitoring of physicochemical evolution and microbial community dynamics, this study evaluated the differential efficacy of these additives in enhancing composting performance. Key findings revealed that vermiculite treatment achieved superior humification levels, concurrently facilitating substantial stabilization of heavy metals, particularly Zn (31.59 % conversion rate to stable fractions) and Cr (60.49 % conversion rate to stable fractions). These effects correlated strongly with the enrichment of Firmicutes. Redundancy analysis indicated electrical conductivity (EC) as the dominant driver of bacterial community restructuring after the thermophilic stage. While the morphological transformation of Zn and Cr showed significant associations with humic substances, the speciation distribution of Cu exhibited stronger linkages to bacterial community structure. Correlation analysis indicated that most Firmicutes played a crucial role in organic matter degradation and humic substance synthesis, whereas Pseudomonas demonstrated nitrogen conservation capability. This work provides theoretical foundations and practical insights for the resource utilization and harmless treatment of cattle manure.