Potentials of energy saving for cucumber crop production in different types of greenhouse in China

Energy is consumed in forms of greenhouse construction and crop management inputs for greenhouse crop production. Energy saving in greenhouse crop production depends on greenhouse structure and ways of crop managements. To what extent that energy consumption can be reduced is important information for assessing economic feasibility of greenhouse investment and applying cost effective technologies for greenhouse construction and crop management. To identify this extent, life cycle assessment (LCA), input-output analysis, models of crop growth and energy consumption for climate control were used to estimate specific energy for cucumber production in three types of greenhouse (plastic tunnel, lean-to greenhouse and multi-span plastic greenhouse). Simulation analysis on changes of specific energy was implemented for the following scenarios: (1) for the lean-to greenhouse, using the traditional structure composed of bamboo-tube roof frame and clay walls as reference, (1.1) replacing bamboo-tube roof frame with steel-tube roof frame; (1.2) replacing both bamboo-tube roof frame and clay walls, respectively, with steel-tube roof frame and brick walls; (1.3) combining (1.1) with improving resource use efficiency from current level (nitrogen use efficiency NUE: 45%, water use efficiency WUE: 19%) to advanced level (NUE: 88%, WUE: 38%); (1.4) combining (1.2) with improving resource use efficiency; (2) only improving resource use efficiency for crop management in all three types of greenhouses. Climate data from 225 stations in China were used to run the models of crop growth and energy consumption for climate control. The simulation analysis showed that scenario (1.1) and (1.3) decreased the specific energy, respectively, by 5.3-6.4% and 14.7-19.1%. Scenario (1.2) and (1.4), however, increased the specific energy, respectively, by 11.5-14.7% and 0-5.9%. Under scenario (2), the specific energy decreased by 3.6-17.5% in plastic tunnel, by 7.4-14.2% in lean-to greenhouse, and by 0.1-5.5% in multi-span plastic greenhouse. Improving resource use efficiency in plastic tunnel, composing of steel-tube roof frame and improving resource use efficiency in lean-to greenhouse, and improving climate control in multi-span plastic greenhouse have the greater potentials in energy saving for greenhouse crop production in China.