A pathway-resolved national model for quantifying environmental loads from pet dog waste: a case study of South Korea.

Pet dog waste (PDW) represents an emerging waste stream linking municipal solid waste and urban water systems, yet its pathway-specific environmental loads remain unquantified at national scale. We develop a pathway-resolved mass-balance model for South Korea that allocates PDW into three disposal routes (volume-based waste (VBW) as a fraction of municipal solid waste, sewer, and soil-water pathways) and four material categories (urine, feces, pads, bags). Using nitrogen and phosphorus (N and P) concentrations in excreta, product-specific plastic composition, wastewater removal efficiencies, and soil-to-water delivery ratios, we quantify freshwater nutrient loads and VBW-related CO₂ emissions. Nationally, VBW accounts for 57.5% of total PDW, soil-water releases 30.2%, and sewer inputs 12.3%. Freshwater eutrophication is dominated by diffuse outdoor releases, delivering 2.20 kt N/yr and 157 t P/yr, primarily from urine runoff and uncollected feces. Climate impacts from PDW (45.9 kt CO₂/yr) arise mainly from pad plastics. Sensitivity tests show strong dependence on pad usage, feces dry-matter content, and hydrologic delivery. The model provides a reproducible framework for integrating PDW into nutrient management and solid waste planning and highlights the need for pathway-specific mitigation strategies.