Integrated assessment of physicochemical and structural changes during composting and vermicomposting of cattle and sheep manure with additive treatments

This study investigates the effectiveness of biochar (B-5%, 10%), carbonatic fire clay (FC-5%, 10%), and manganese dioxide (MnO2-0.5%, 1%) in enhancing the composting and vermicomposting of cattle and sheep manure over 120 days. Temperature profiles reached peak values of 65–67 °C for cattle manure and 70–72 °C for sheep manure under FC-10 treatment, indicating optimized microbial activity associated with improved aeration and porosity. Mass loss peaked at 65–70% with B-10 and FC-5 in sheep vermicompost, driven by earthworm-mediated degradation, whereas FC-10 stabilized mass loss at 45–50%, promoting organic matter stabilization and humification. Cation exchange capacity (CEC) increased markedly in sheep vermicompost under FC-10 treatment, reaching an experimental maximum of approximately 540 cmol(+) kg−1 and a modeled asymptotic value of 311 cmol(+) kg−1, reflecting enhanced nutrient retention. Parabolic kinetic modeling revealed rapid hemicellulose degradation (r = − 0.9989 with FC-10), moderate cellulose decomposition (r = − 0.5767), and substantial lignin reduction (r = − 3.548 with MnO2-1), highlighting the distinct and complementary roles of microbial and oxidative pathways. Overall, these results demonstrate that biochar, carbonatic fire clay, and manganese dioxide contribute through complementary mechanisms to different stages of organic matter transformation, offering a promising strategy for improving compost quality and sustainable manure management.