The environmental impacts of the growing global trade with organic products during both production and transport have gained increasing attention. One of main organic export products in China namely soybean was studied using the life cycle assessment method, the DNDC model and on site survey in the northeastern region to quantify the impact of resource depletion and environmental impact. The environment hotspots in the life cycle for three different types of soybean production were identified: Exported Organic Soybean (EOS), Locally-consumed Organic Soybean (LOS) and Locally-consumed Conventional Soybean (LCS).
Data for agricultural inputs were obtained directly from 29 organic and 14 conventional soybean farmers who filled in questionnaires for the growing season 2006-2007. Data on the transportation and fertilizers were obtained from the retailers and the trade company. For the DNDC model, data for soil conditions and climate were obtained from the local government, own analysis selected samples and from the organic trade company. This study focused on global warming, resource depletion, eutrophication, acidification and ecological toxicity as impact categories for LCIA. Normalization references for global warming, eutrophication and acidification are specific for China whereas normalization references for resource depletion and ecological toxicity are global due to lack of emission data for those two categories. Expert judgment was used to get the weighting factors.
The results showed that resource depletion, acidification and global warming potential accounted for a considerable fraction of total environment impact with about 30% for each item while eutrophication and eco-toxicity only accounted for less than 10% respectively. EOS showed the highest value for energy consumption compared to LOS and LCS. Transportation contributed the most and the fraction in EOS can reach as high as 95%, but it was also considerable for LCS and LOS. Besides, production of fertilizer depleted 11% of the resource for LCS.The EOS and LCS showed almost the same acidification potential followed by LOS. SO₂ emitted from transport stage was the main reason for this, which was due to energy consumption and burning of fuel. During production, conventional soybeans emitted 716 gSO₂-equiv./t compared to 590 gSO₂-equiv./t from organic soybeans mainly due to more machinery hours in the field.The agricultural input production stage emitted 788 g SO₂-equiv./t for conventional soybeans, especially for the production of phosphorous fertilizer. EOS had the highest global warming potential and locally-consuming soybeans minimized carbon dioxide emission. The carbon dioxide emission from transport ranged from 784 kg CO₂-equiv./t to 1477 kg CO₂-equiv./t which accountted for a large fraction in the life cycle.Eutrophication potential of LCS was 1.8 and 1.4 times greater than that from LOS and EOS.The agricultural input production stage was the most significant and contributes to 55% of the total amount. In the farming stage, organic soybeans emitted almost 640 g NO₃-equiv/t which was greater than conventional soybeans because of higher input of N. In LCS, ecological toxicity potential accounts for 8% of environmental impact.Considering all the factors for environment impact, LOS was most environment-friendly option which can reduce the environmental impacts by 33% and 31% compared to EOS and LCS.Locally produced organic soybeans consumed in China could reduce CO₂ emission and energy consumption by 47% and 33% respectively. This could also decrease acidification and eutrophication risk by 19% and 46% compared to EOS and LCS. LOS would therefore not only decrease resource depletion, but also met the requirements for pollution reduction. Thus, locally consumed organic products are environmentally favorable.