Biochar-amended poultry mortality composting to increase compost temperatures, reduce ammonia emissions, and decrease leachate's chemical oxygen demand

Proper disposal of animal mortalities is essential in preventing disease transmission and protecting air and water quality. Composting is often used to manage both routine and diseased poultry mortalities. The objectives of this pilot-scale study were to test if adding wood-based biochar to poultry mortality compost could 1) increase compost temperatures, 2) reduce ammonia emissions, 3) decrease leachate's organic content, and 4) enhance the nutrient content of the final compost. Biochar ratios at 0, 1, 5, 10, and 15% (fresh weight) were co-composted with chicken mortalities and woodchips for 11 weeks (three heating cycles). Results indicated that the biochar amendment significantly increased (3.4–7 °C) the maximum temperatures reached during the composting compared to those of control test units without biochar. Biochar amendments at 5, 10, and 15% resulted in the prolonged periods of temperature over 67 °C to inactivate the highly pathogenic Avian influenza (H7N1), and a reduced cumulative chemical oxygen demand of the leachate by 80.4 ± 3.07%, on average. Biochar amendment at 10 and 15% significantly reduced the cumulative ammonia emissions by 40.4% and 56.8%, respectively. Biochar amendment at 15% increased (34.7%) the total nitrogen content of the final compost. It was concluded that adding biochar, at a minimum of a 5% ratio, is recommended to improve the poultry mortality composting process.