Identifying the resource use and circularity in farm systems: Focus on the energy analysis of agroecosystems

Abstract

An innovative method is described, assessing the energy flows in farm systems. These systems represent both a socio-economic activity and an agroecosystem. Both market and ecosystem flows are inventoried, focusing on farm agroecosystem circularity of the reinvested biomass. An original system representation is proposed, where process and energy storage sub-systems are distinguished. Biotic energy storage, identified as an Associated Ecosystem (AE) is included. Soil mineralization, reflecting soil activity, was selected as a proxy for services provided by the AE. The present approach was tested on an existing French mixed farm case study. Contrasting scenarios were proposed to test the model and the two sets of selected indicators. EROIs (Energy Return On Energy Invest) evaluate the current system performance through resource use efficiency. Circularities reflect the system resilience. Circin (Inflow Circularity) indicates the system self-sufficiency and the extent to which the farm activity is based on the AE. Temporal stability is assessed by the steadiness of the Circin versus Circout (Outflow Circularity) relationship. The Crop production scenario presents best performance. Specialized and intensive systems present lower Circin values. Furthermore, contrasting Circularities were observed for the intensive breeding scenario, while homogenous results were obtained for the extensive mixed-farming scenario. This method takes a new step towards the integration of circularity and ecosystem support functions in the energy analysis of farm systems. Firstly, it provides indicators of performance and resilience. Secondly, as a key feature for sustainable agriculture, it highlights the relationship between agricultural activity and its associated ecosystem.