Assessing life cycle impacts from toxic substance emissions in major crop production systems in Thailand

Toxicity-related impacts are often omitted or poorly represented in environmental performance assessments of agricultural production systems. Existing studies usually focus on selected aspects, such as pesticides, and rely on the wider range of relevant emissions and life cycle operations, hampering decision support that considers trade-offs and regional characteristics. The present study comprehensively assesses life cycle toxicity impacts of major crop production systems in Thailand, considering all relevant supply chain operations, farm-level field operations, and downstream crop residue burning. Impact characterization factors for farm-level and downstream processes have been specifically parameterized for Thai conditions. All impacts were translated into damage costs for different scenarios based on Thailand's action plans for agricultural production, air pollution control and energy consumption, to facilitate targeted decision support at the national level. Toxicity-related impacts vary considerably across Thai crop production systems, ranging from a few hours (cassava, sugarcane, palm oil) to 1.5 months (rice) of average individual human lifetime loss, and from 15 (sugarcane) to 147 (rice) million species fraction lost over time and water volume. Combined, these crop systems caused damage equivalent to >3.5 trillion Thai Baht in 2019, dominated by pesticide and manure/fertilizer-related farm-level emissions due to human health damage, and by fertilizer and fuel-related supply chain operations due to ecosystem quality damage. The scenarios could substantially reduce toxicity-related impacts on humans and ecosystems across almost all considered crop production systems, mainly through adopting integrated approaches, including optimal use of crop residues and swine manure, and reducing pesticide use and diesel consumption for field operations. Our results demonstrate that including all life cycle operations and regionalized impact factors is crucial to respectively identify major trade-offs across production scenarios and account for country-specific characteristics. The proposed approach is suitable to inform national strategies supporting more sustainable crop production, and can be adapted to consider other production systems and regions.