Impact of agrochemical emission models on the environmental assessment of paddy rice production using life cycle assessment approach

Rice is a staple crop that meets 21% of worldwide human calorie requirements. Eighty percent of produced rice in Iran comes from the northern part of Iran. Considering the importance of northern regions in meeting the demands for rice, and increased consumer awareness on environmental sustainability, this aspect should be considered and investigated. Life cycle assessment (LCA) approach is a potential tool to quantify the environmental sustainability of agri-food systems. But modeling the agrochemical emissions is a challenge for LCA-practitioners to build a reliable inventory for fertilizers and pesticides. This study aimed to investigate the impact of agrochemical emission models on the environmental impacts of paddy rice production in paddy fields in three major regions in the north of Iran. Emission models (Margni and PestLCI for pesticides and IPCC and Brentrup for fertilizers) were selected based on the availability of site-specific information and based on that two scenarios were defined. Scenario I was defined for the cases in which there is no enough site-specific information and scenario II is defined based on the availability of on-site information. ReCiPe2016 (H) methodology on the midpoint level was used for quantifying the environmental impacts. Results showed that rice seed production, diesel fuel, urea, phosphate fertilizer, and Diazinon are the major environmental hotspots in paddy rice production. Results revealed that the general emission models used in scenario I overestimated the impact scores in marine eutrophication (90%), freshwater ecotoxicity (87%), marine ecotoxicity (44%), non-cancer human toxicity (26%), and terrestrial ecotoxicity (10%), while underestimation was found in some impact categories such as ozone depletion (115%), terrestrial acidification (21%) and global warming (4%). It shows the importance of emission models on achieving reliable impact scores in each environmental impact category. About rice straw management strategy, utilizing straw as livestock feed can mitigate the emissions of greenhouse gases to the air by 30% to 38% compared to burning paddy residue on the farm.