Total embodied energy requirements and its decomposition in China's agricultural sector

Humanity faces the important challenge of understanding and integrating human and natural processes, including agriculture. In China, the scarcity of arable land (0.09 ha per capita), increasing population, and migration of the workforce to cities pose a significant challenge for food security. Agricultural energy productivity has therefore become a key concern. In this study, we used input-output analysis to measure energy productivity at a national agro-ecosystem scale for China using the total embodied energy requirement (TEER) to reveal hidden energy flows. We introduced a structural decomposition technique that reveals how changes in TEER for the agricultural sector were driven by changes in energy-use technology and the inter-relationships among two agricultural sectors (farming and animal husbandry). The results will help both policymakers and farmers to improve the efficiency and environmental compatibility of agricultural production. Declining TEER for both sectors means that China's overall agro-ecosystem has increased its energy productivity since 1978 due to improved relationships between the agricultural sectors and increased use of biological energy. However, the net positive energy income decreased in the farming sector and an increasing proportion of fossil energy use, accompanied by increased energy income in the animal sector, provide incentives to increase yield and decrease labor by using more fossil energy, thus raising more animals in the animal husbandry sector. Overuse of fossil energy since 1990 has resulted in decreasing fossil energy efficiency, requiring immediate measures to improve the use of fossil-fuel-intensive materials such as fertilizers. (C) 2008 Published by Elsevier B.V.