Energy use efficiency and greenhouse gas emissions of oil crops in China

Energy is a major component in enhancing agricultural productivity. Accounting for energy efficiency at the production stage of crop is essential for achieving sustainable agriculture. Due to the high level of production and consumption of oil in China, it is of great importance to pay attention to energy consumption and its negatively environmental impacts in the oil production process. Measures of optimizing energy utilization structure, reducing excessive and ineffective energy consumption and improving energy utilization efficiency can be used, in order to increase income, save cost and reduce greenhouse gas emissions synthetically. Academically, a large number of previous studies have contributed to energy use and environmental impacts in the production of oil crops, fruits, vegetables, and food crops on various scales. However, there is a lack of studies related to energy use efficiency and greenhouse gas emissions in oil production which concentrate in major oil crops production areas nationally so far. Generally, in terms of models used in relevant study areas, methods including life cycle assessment (LCA), data envelopment analysis (DEA), process analysis, energy analysis have been used commonly, which provide valuable references to the present study. Given that oil crops production is inherently a life process, this paper combined LCA+DEA methods to estimate the energy utilization efficiency and greenhouse gas emissions of oil crops, which helped to rank efficient and inefficient provincial production units. In further, the underlying reasons which caused inefficient energy use were deeply identified in different provinces. Additionally, for purpose of practical application, this paper explored the possibility and potential of energy saving and GHG emission reduction in each province. The results showed as follows. 1) There was no significant difference in the output capacity per unit energy consumption among the three studied oil crop systems. However, the energy use efficiency of three oil crops displayed remarkably differently, which showed peanut > oilseed rape > soybean. 2) Among the three oil crops, peanut had the highest GHG emissions 874.96 kg(CO₂ eq)∙hm⁻², followed by oilseed rape 660.16 kg(CO₂ eq)∙hm⁻² and soybean 507.07 kg(CO₂ eq)∙hm⁻². In addition, the contributions of substantiality inputs and agricultural operations to GHG emissions varied greatly from different oil crops. Specifically, the significant GHG emission source of oilseed rape and peanut was fertilizer. Nevertheless, contribution of fertilizer, diesel fuel and irrigation to the GHG emissions of soybean showed less difference. 3) There was great potential for energy utilization optimization and GHG emission reduction. Estimates resulted from this study displayed that about 11.97%, 16.38% and 15.89% of resources invested to oilseed rape, soybean and peanut in inefficient provinces could be saved respectively, which were capable of reducing 20.60−616.32 kg(CO₂ eq)∙hm⁻² GHG emissions as well. Therefore, it is necessary to optimize the energy utilization structure of low efficiency areas according to the actual situation, and explore the production mode of double optimal yield and carbon emissions. This will play an important role in saving money and increasing income for regional oilseed cultivation, as well as green development.