Assessing the Environmental Impacts of Soybean [Glycine max (L.) Merril] Cultivation in the Eastern and Central Regions of Mazandaran Province using Life Cycle Assessment

Food security and sustainable agriculture are among the most challenging issues for the human being in the present age. These daunting challenges have arisen in the face of dramatic population growth as well as rising living standards, lifestyle, and, as a result, increased demand for a variety of foods. Due to limited water resources and arable lands, to achieve more production, it is necessary to increase the yield per unit area by using more materials (e.g., chemical fertilizers, pesticides, and fossil fuels) and energy. Obviously, in addition to the higher cost, it will lead to irreparable environmental consequences. In this regard, to achieve more sustainable production of agricultural products, there is a need to carefully evaluate the environmental status of these products in order to identify environmental hotspots to optimize them. Due to this, a study was conducted to assess the environmental damages to the soybean production system in different cities of Mazandaran province with a life cycle assessment (LCA) perspective. 

In the present survey, LCA approach was applied to evaluate the environmental impact and determine the most important hotspots of soybean produced in the cities scale of Mazandaran province (13 cities with soybean cultivation). LCA is a method that examines the environmental impacts associated with a product (or process) throughout its lifetime by accounting for resource consumption and pollutant emissions. For this purpose, the farm gate was considered the system boundary. Necessary data for LCA inventory were also obtained through face-to-face interviews with 303 farmers in 2019 and the EcoInvent 3.5 database in SimaPro 9.0.0.49 software. The potential environmental impacts were assessed by the IMPACT2002+ (v2.15) model in the software based on 1 ton of soybean seed produced as the functional unit (FU). Finally, impact assessment results of the soybean production system were presented in four environmental damage groups: human health, ecosystem quality, climate change, and resources. 

The findings revealed that soybean cultivation in the region and under the current conditions of inputs consumption has the highest impact on human health indicators that direct emissions from diesel fuel combustion and application of chemical fertilizers in the field play a major role in this damage category. Direct emissions from field operations claimed the highest share (>51%) in increasing global warming potential, which was mainly a result of CO2 emissions from burning diesel fuel. In addition, the findings of the present study showed that diesel fuel, followed by nitrogen fertilizer, had the most substantial role in the resources damage category. More generally, the total environmental damage for the production of 1 ton of soybean seed in surveyed cities ranged from 228.76 to 439.77 mPt, among which the cities of Galugah and Qaemshahr (228.76 and 261.18 mPt, respectively) had the least and Amol, and Sari (438.06 and 439.77 mPt, respectively) had the most value. To sum up, the LCA approach has been able to quantify the contribution of the soybean production system in causing environmental damage in the form of different damage categories by considering the amount of each of the inputs and their emissions based on a specific FU. 

In general, it can be concluded that diesel and chemical fertilizers inputs and direct emissions caused by their consumption on farms were the most substantial environmental hotspots. These factors, in turn, arise from the mismanagement of soybean farms in Mazandaran. Hence, it seems that efficient management practices by informing farmers and support of the authorities to provide appropriate facilities to farmers can be an important step toward reducing the environmental consequences and developing the cultivation of this valuable crop in the region. 

Acknowledgments

The authors would like to acknowledge the financial support of Tarbiat Modares University and the assistance of the esteemed officials of Sari Agricultural Sciences and Natural Resources University, Agriculture-Jihad Organization of Mazandaran province, and especially the honorable farmers of this province to collect data for this study.