The fate of pollutants in the co-composting of natural mineral biochar and animal manures in an intermittent aeration and mixing bioreactor (IAMB)

Animal manures (AMs) are widely utilized as organic fertilizers but often contain significant levels of emerging pollutants, posing environmental and health risks. This experimental study investigated the impact of 650-million-year natural mineral biochar (NMB) and animal manure (CWM:PUM) on the fate of pollutants in the process of intermittent aeration and mixing composting. 12 treatments were monitored over 60 days to evaluate the fate of pollutants, nutrients, and environmental risks. The cumulative temperatures (°C) recorded for treatments T1–T12 were 897, 858, 836, 981, 926, 898, 1007, 999, 959, 1056, 1025, and 972, respectively. At the start of the process, the Zn concentrations in treatments T1, T4, T7, and T10 were 197.15, 336.32, 287.53, and 244.16 g/kg, respectively. By day 60, they had decreased to 185.78, 296.14, 197.52, and 129.58 g/kg, respectively. Cu concentration in mature compost was 228.31, 109.36, 76.11, and 131.5 g/kg. The removal efficiency rankings varied across treatments: in control: Zn > Cu > Cr, in 5% NMB: Cr > Cu > Zn, and in 10% and 15% NMB: Zn > Cr > Cu. Zn, Cu, and Cr showed significant reductions due to adsorption, surface complexation, and pH-mediated mechanisms, with final concentrations below the USEPA standards. This study highlights the efficacy of NMB in improving compost quality, reducing pollutant bioavailability, and mitigating environmental risks, underscoring its potential as a sustainable solution for managing animal manure.