Geospatial optimization of compost distribution for cropland under California’s organic waste diversion strategy

Composting has emerged as a key methane mitigation strategy. California has enacted one of the world’s most ambitious organic waste diversion mandates (SB 1383), requiring a 75% reduction in landfill disposal by 2025 compared to 2014 waste disposal levels. While previous studies have demonstrated the climate benefits of this unprecedented regional shift to composting, limited attention has been given to the logistical feasibility of delivering compost to croplands under real-world infrastructure. A critical knowledge gap remains in understanding the spatial alignment between waste generation, processing capacity, and cropland demand. Here we develop a geospatial optimization model that simulates statewide compost logistics using detailed road routing and facility-level data. The model estimates mass-weighted average haul distances of 46 km for organic waste and 80 km for compost, capturing regional variation in supply and demand. Results show that minimizing cost and emissions while meeting diversion targets requires distributing compost from coastal cities to inland agricultural regions. Nearly 70% of compost is allocated to Southern California and the San Joaquin Valley — regions prioritized for soil restoration. These findings provide a system-level foundation for planning compost infrastructure to support California’s climate and waste diversion goals. • Cropland explicitly modeled as primary compost end user. • Resulted 80 km average compost delivery distance aligns with marketability threshold. • Detailed road-routing logistics with facility location and ∼ 3 km 2 cropland parcels. • Statewide compost networking optimized for cost and GHG emissions. • Regional variations in organic waste supply and compost distribution.