Environmental life cycle assessment of long-term organic rice production in subtropical China

Organic farming is considered as a promising solution for reducing the environmental burden related to agricultural practices. China is one of the top-five countries with the largest organic area in the world and produces a major part of the world's organic rice. Rice cultivation causes a considerable environmental impact and changing from conventional to organic rice cultivation might therefore have a potentially great impact. Meanwhile, it takes time for the organic farming systems to reach a new steady state after conversion to organic. Thus, the environmental profile of the organic products will change over time and it is therefore important to examine whether the difference to conventional will be reduced (and disappear) or be increased over time. The aim of the present study was therefore to assess the environmental impact of organic rice production 5 (OR5), 10 (OR10) and 15 (OR15) years since conversion and compare it to conventional rice (CR) in subtropical China. The life cycle assessment (LCA) method was used to assess environmental impact of rice production systems with regard to nine environmental impact categories: Non-renewable Energy Depletion (NED), Water Depletion (WD), Land Occupation (LO), Global Warming Potential (GWP), Acidification Potential (AP), Eutrophication Potential (EP), Aquatic Toxicity Potential (ATP), Human Toxicity Potential (HTP) and Soil Toxicity Potential (STP). Overall, the results show that the conventional rice production system had the highest comprehensive environmental impact indices (9.65), more than 10 times that of the organic ones. Interestingly, the results showed that the environmental impact indices in the organic rice systems decreased over time from 0.80 (OR5), 0.72 (OR10) to 0.68 (OR15), and thus increased the difference to conventional over the years. The conventional rice had higher impacts from NED, WD, AP, EP, ATP, and HTP, while organic rice had higher LO, GWP and STP indices. The largest environmental index was ATP for conventional and WD for organic rice. Based on this study, organic rice systems have the potential of being recommended as sustainable agricultural practices in comparison with conventional practices. Furthermore, the present study indicated that the difference in the environmental profile of organic versus conventional agricultural products might be underestimated when analyzing organic system that has not yet reached their steady state.