Effect of matured compost and exogenous microbial inoculants on the composting process of digestate eluted from dry anaerobic digestion

Abstract

Abstract Biogas and digestate can be produced by anaerobic digestion of pig manure and straw. However, further treatment of digestate should be carried on. The digestion efficiency is affected by the addition of extra biodegradable materials or inoculants. This study was conducted to reach a less emission and higher efficient of the composting process. The windrow composting of the digestate by adding mature compost and exogenous commercial microbial inoculants was performed by two assays per variation. The composting process showed that the digestate treated with exogenous microbial inoculants reached a 10-20% higher organic matter loss than the digestate without exogenous microbial inoculants. The plant-nutrients (N, P, K) were significantly increased due to the positive effect of exogenous microbial inoculants, especially the HK microbial inoculants. Adding matured compost can reduce the plant-nutrients loss caused by leaching from digestate, which is with high moisture content. Meanwhile, the concentrations of toxicant heavy metals in digestate were also increased after composting due to organic compounds decomposition and concentration effect. Additionally, the heavy metals concentrations in compost are still under the standard. In general, the results illustrated that windrow composting can be added to enhance the composting efficiency and resource recovery of pig manure and straw.