Insights into Physiochemical and Biological Characteristics of Pig Manure During Anaerobic Digestion and Sheep Manure During Composting

The physiochemical and biological properties of animal manures are crucial factors in resource utilization. Herein, the physiochemical and biological characteristics of pig manure during anaerobic digestion and sheep manure during composting were investigated. The animal manures were rich in heavy metals. Zn was the most abundant heavy metal, in the range of 586.9–2069 mg/kg in the animal manures. After anaerobic digestion, the contents of cellulose, hemicellulose, and lignin increased by 59.97%, 6.90%, and 171.81%, respectively, while the contents of NH4+-N, NO3−-N, total nitrogen, total phosphorus, and K decreased by 5.50–48.27% in the pig manure. The contents of NH4+-N, NO3−-N, total phosphorus, and K increased by 20.56–61.82% in the sheep manure after composting. The contents of all heavy metals increased in the compost, especially the Zn content which increased by 145.6%. Potential pathogenic bacteria including Pseudomonas, Clostridium sensu stricto 1, Acholeplasma, Tissierella, and Halomonas were abundant in the animal manures. Composting could inactivate pathogenic bacteria in the animal manures well, while a large number of pathogenic bacteria still remained in the digestate if the solid retention time was short in anaerobic digestion. The findings would be helpful for understanding the characteristics of animal manures and developing effective treatment and resource utilization technologies.