Exergy analysis of Chinese agriculture

Along with the growing population scale and improving diet structure, a great challenge has been faced to reconcile food supply, resource use and environmental impact in contemporary agriculture. This paper presents an in-depth exergy analysis of Chinese agriculture covering cropping, forest, stockbreeding and fishery over the period of 2001-2015. The resource, environmental and economic performance of the agricultural system are illustrated by accounting all the major exergetic fluxes, which include free nature resources input, purchased economic investments, waste emissions or virtual environmental inputs, and harvested yields of agricultural products. Chinese agriculture has experienced accelerating transition from a self-supporting mode to a modern energy-intensive pattern, which is characterized by lower renewability index, higher non-renewable resource consumption and economic investment ratio, and larger waste emissions and environmental resource input. The improvements of resource use efficiency and total agricultural productivity are also identified as indicated by the evolution of resource yield ratio and system transformity. In 2015, as to 100 units of agricultural yield, there were about 109 units of purchased resource input including 18 units purchased nonrenewable resources, 748 units of free natural resource input and 21 units of environmental impact. Exergy analyses capture the resource and environmental performance of agricultural ecological economic system by pinpointing the real exergy dissipation and cost processes, which could help policy makers to couple biophysical concepts more robustly for improving resource use efficiency and achieving sustainable development of Chinese agriculture in the 21 st century.