Concomitant management of solid and liquid swine manure via controlled co-composting: Towards nutrients enrichment and wastewater recycling

•The novel SE-M-R co-compost could potentially lower nitrogenous gas emission.•TN, NH4+-N and NO3--N nutrients were enhanced by the novel SE-M-R co-compost.•Controlled co-composting of SM and LM can simultaneously achieve LM recycling.•Compared to M-R, total N, P, K, cu and zn were enriched in SE-M-R final compost. Co-composting of solid manure (SM) and liquid manure (LM) is a new practice in livestock wastes recycling process and management. However, this practice is laced with various challenges including undesired leachate production, greenhouse gas emissions and characteristics poor nutrient quality of the final compost. Pragmatic utilization of the resource potential availed by combined LM and SM co-composting will be a game changer strategy for direct recycling of livestock wastes and reducing environmental contamination. By adapting a recently proposed LM addition model, we systematically investigated the promoting factors (thermophilic duration, organic matter (OM) degradation, and so on) necessary for successful co-composting of SM and LM, and for the first time examined the nutrient enrichment model essential to achieving final compost recyclability. Compared to the conventional SM co-compost, the proposed SM and LM controlled co-composting process elongated the thermophilic duration, reduced leachate generation, enhanced OM degradation, and simultaneously induced potential nutrients enrichment as evidenced by the nutrient balance analysis. The concentrations of TN, TP, TK, Cu and Zn in the controlled final compost were relatively enriched by 21.7 ± 2.16%, 12.1 ± 0.14%, 12.6 ± 0.16%, 11.0 ± 0.16% and 11.3 ± 1.24%, respectively. In addition, the controlled co-composting technique allowed for reduction in nutrients loss due to volatile N, estimated at 28.8% decrease in N loss rate relative to the conventional SM co-compost, and approximately 1.8 t/day of livestock wastewater can be effectively managed. The study conclusively demonstrated that concomitant utilization of liquid and solid manure presents an environmental friendly and unique advantage for simultaneous management and recycling of livestock wastes.