Life cycle environmental impact assessment of rice-crayfish integrated system: A case study

Abstract

Rice-crayfish integrated system (RCIS) as a sustainable agricultural system has been widely and rapidly promoted in China. However, the environmental impact potential of RCIS is still unknown compared with conventional rice monoculture system (RM). A life cycle assessment (LCA) methodology was applied to characterize the environmental performance and potential improvement opportunities related to RM and RCIS, and a questionnaire survey of 300 farmers was carried out in Qianjiang city, China. Seven environmental impact categories, including non-renewable energy depletion (NED), global warming potential (GWP), acidification potential (AP), eutrophication potential (EP), human toxicity potential (HTP), freshwater toxicity potential (FTP) and soil toxicity potential (STP) were involved. Results showed that the NED and GWP were primary caused in off-farm stage, but the other environmental impact categories, including AP, EP, HTP, FTP, and STP were mainly occurred in the on-farm stage whether in RM or RCIS. Despite decreased chemical fertilizers and pesticides application in rice growing subsystem, the NED, GWP, AP, EP, HTP and STP were increased in RCIS by 84.30%, 89.37%, 61.88%, 95.87%, 98.06% and 70.78%, respectively, compared with RM. The crayfish farming subsystem produced more resources consumption, pollutant emissions and toxicity potential, with feed production and input being the primarily contributor to environmental impact categories in RCIS. The total environmental impact index from RCIS was 90.95% higher than that from RM. It is worth noting that obviously higher EP was produced in crayfish farming subsystem of RCIS, indicating that pollutant emissions resulted from aquaculture farming might be ignored and hidden in paddy fields. Based on these results, it is suggested that improving aquatic feed utilization, providing necessary technical training and guidance to farmers, and formulating environmental pollution risk control policies and punitive measures might be taken into consideration to ensure the effective use and sustainable development of rice-aquatic animal integrated system.