Integrated life cycle assessment of improving saline-sodic soil with flue gas desulfurization gypsum

A large quantity of flue gas desulfurization gypsum (FGDG), a by-product of removing sulfur from combustion gases in coal-fired power generation plants, was produced in the world. Improving saline-sodic soils with FGDG is one of the effective ways to utilize FGDG. However, the use of FGDG has severe impacts on the environment. With growing application of FGDG for improving soils, there is an increasing necessity to analyze the environmental impact on the entire agricultural application process. Life cycle assessment (LCA) is useful for comparing the potential risks of different environmental impact categories and stages. Traditional LCA methods have some limits in comparing various schemes, while the Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) has its unique advantages in multi-objective decision-making. Therefore, this study identified and compared the environmental impacts of four alternative schemes in three stages using LCA combined with TOPSIS. In this study, the environmental impact of improving 1 ha saline-sodic soil was assessed, and a sensitivity analysis was conducted to analyze the effects of the changes in heavy metals in FGDG and in irrigation. The highest impact category was water consumption, with a weighted environmental impact value of 2.20 × 10−1 and a contribution rate of 42.216%. The second-highest environmental impact category was soil toxicity, with a weighted environmental impact potential value of 8.04 × 10−2 and a contribution rate of 15.429%. The soil toxicity was mostly from the application stage, while the water and energy consumption were mainly from the irrigation of planting stage. Acidification and eutrophication were mainly from fertilizer applications. Effective measures, including scientific use of fertilizers and pesticide, reasonable irrigation and strict control of heavy metals in FGDG should be employed to mitigate environmental risks during the agricultural application of FGDG. This study constructed a framework for the environmental impacts of improving saline-sodic soils with FGDG integrated with TOPSIS, and can be considered as an effort to advance the application of LCA.