Evaluation of ecological footprint of straw resources utilization based on emergy theory: A case study of typical rice-wheat rotation region in Chengdu Plain

Using Guanghan City and Dayi County as typical regions of rice-wheat rotation system in Chengdu Plain, emergy and ecological footprint theories were applied in the determination of the utilization status of straw resources based on statistical and survey data in 2011. Firstly, the emergies of different ways of straw utilization were calculated and the values of ecological footprint and capacity per capita then estimated and analyzed using the ecological footprint analysis method. The results showed that the values of per capita ecological footprint of rice and wheat straw resources in Guanghan City were 0.066 1 hm² and 0.034 2 hm² and the per capita ecological surpluses corresponding were 0.017 8 hm² and 0.008 1 hm², respectively. As for different utilization ways, the ecological footprint per capita of rice straws was in the order of fertilizer > raw materials > incineration and other ways > feed > biogas; for wheat straws, it was in the order of fertilizer > incineration and other ways > raw materials > biogas > feed. The values of per capita ecological footprints of rice and wheat straw resources in Dayi County were 0.051 6 hm² and 0.020 9 hm² with corresponding per capita ecological capacities of 0.061 0 hm² and 0.021 7 hm² and per capita ecological surpluses of 0.009 4 hm² and 0.000 8 hm², respectively. As for different utilization ways, the ecological footprint per capita of rice straws was in the order of raw materials > fertilizer > biogas > incineration and other ways > feed; for wheat straws it was in the order of fertilizer > incineration and other ways > raw materials > biogas > feed. The above results indicated that there still existed some room for reutilization of straw resources in Guanghan City and Dayi County. Specifically, if the unused part of the current straw resources were reused fully, it would greatly promote agricultural development which could lead to significant economic, ecological and environmental benefits.