Physico-chemical changes and maturity evaluation of composts from wood residue mixed with sewage sludge and chicken manure

Purpose Using the effective approaches for modifying the recycled wood as a novel bulky agent improves the quality of soil amendment. This study aimed to compare the stability and maturity of the soil amendments produced by the compostation of forest industrial waste and sewage sludge on seed germination. Method Three materials, namely sawdust, sewage sludge, and chicken manure were mixed at different ratios (dry weight basis) to reach the initial bulk density of ۰.۴۰ Kg.L-۱, the temperature of ۳۰ °C, the C/N ratio of ۲۵, and the moisture content of ۶۰ %. A pilot-scale composting process was applied to monitor the aeration rate, temperature, and moisture contents during the process over time. The comparison of physico-chemical, phytotoxicity, and germination indices among the samples was performed in three repetitions. Results The results of this study indicated that the sustainable conditions (i.e., the temperature of ۷۰ °C, aeration rate of ۰.۳۰ L.Kg-۱DM.min-۱, and moisture content of ۵۰-۶۰ %) can have a significant effect on the thermophilic stage for compost curing without any inhibitory repercussion. Increasing the germination index of cress (Lepidium sativum) up to ۷۹ % proved that the toxicity of industrial sewage sludge was declined through the elimination of heavy metals. Conclusion This study revealed that the availability of bulky agents such as wood residue can reinforce the microbial activity by continuously decreasing the C/N ratio to the minimum value of ۱۳.۲.

Keywords:

Wood residue , Industrial sewage sludge , Co-composting , phytotoxicity , germination index