Emergy synthesis of decoupling and recoupling crop-livestock systems under unified system boundary and modified indices

Sustainability assessment of integrated crop-livestock system was crucial for regulating and improving the complex ag-ricultural system. Emergy synthesis (ES) is a suitable tool to assess the sustainability of integrated crop-livestock sys-tems. However, the inconsistent system boundaries and limited assessment indicators caused to subjective and misleading results when comparing the recoupling and decoupling croplivestock models. Therefore, this study defined the rational system boundary of emergy accounting for the comparison of recoupling and decoupling crop-livestock complex systems. Meanwhile, the study designed an emergy-based indices system based on "3R" principles of circular economy. An integrated crop-livestock system including sweet maize cultivation and cow dairy farm in South China was selected as the case to compare sustainability of recoupling and decoupling models under the unified system boundary and modified indices. Results showed that the new ES framework could provide more rational assessment results when comparing the recoupling and decoupling crop-livestock systems. In addition, this study illustrated, through scenario simulation, that the recoupling maize-cow model could be further optimized by regulating the mate-rial flow between subsystems and adjusting the system structure. This study would promote the application of ES method in the field of agricultural circular economy.