Defining Economic and Environmental Typologies across 77 Countries to Prioritize Opportunities for Nonsewered Sanitation.

Lack of access to sanitation is a challenge that persists globally, with low sewerage connection rates in many low- and lower-middle-income countries. Engineered nonsewered sanitation (NSS) technologies can meet treatment requirements without sewers, but their relative sustainability varies across potential deployment sites. Here, we characterize the costs and carbon intensity (CI) of three emerging NSS technologies, two community reinvented toilets (CRTs) and one Omni Processor (OP), across 77 countries, identify sustainability performance typologies, and map typology prevalence in countries across the globe. Locality-specific factors such as wages, diet, and material costs drive regional variability in NSS costs by up to 15-fold and CI up to 2-fold within technologies. Across all three NSS technologies and all scenarios evaluated, costs ranged from 0.01 to 0.36 USD·capita·day and CIs ranged from 8 to 269 kg CO eq·capita·year. Low-cost, low-CI typologies are predominantly in countries with lower human development indices (HDI 2-4), demonstrating alignment between the sanitation need and the NSS opportunity space. Ultimately, the intent of this work is not to imply one-size-fits-all solutions for individual countries; by elucidating key sustainability drivers and defining typologies, this work can support early-stage decision-making for NSS technology research, development, and deployment.