Resource recovery from sanitation to amplify development: Navigating global and local possibilities

Abstract

Recovery of human-derived resources (e.g., nutrients, energy) from sanitation systems has emerged as an approach that may generate progress toward multiple Sustainable Development Goals (SDGs). However, persistent uncertainties and concerns (e.g., economics, social appropriateness) across a variety of scales and settings limit implementation, and failures are common. Decision-makers require more rigorous methods and tools to characterize various sanitation, recovery, and reuse options. Therefore, the overarching goals of this work are to explore and quantify the possibilities, benefits, and challenges associated with resource recovery, and to establish quantitative models and conceptual frameworks capable of contributing to global and local paths forward for sanitation. Specific objectives include (i) estimating recovery’s impacts on resource access; (ii) developing methods to define spatial co-location and transport requirements; (iii) employing spatial methods to assess soil suitability of recovery products; (iv) developing a conceptual framework linking recovery with ecosystem services; and (v) developing a social-ecological systems framework that defines sanitation as a human-derived resource system and supports multidimensional analysis across contexts. The first three objectives examine particular topics associated with resource recovery at a global scale by developing and implementing quantitative models. These analyses point toward locality-specific strategies for deriving the greatest benefit from sanitation investments, while also identifying overarching trends to guide international research efforts. First, resource recovery from sanitation systems that will need to be installed to achieve sanitation SDG targets may considerably improve access to agricultural nutrients and household energy in the least-developed countries, six of which could double or offset all projected nutrient and electricity use. Global potential nutrient gains are an order of magnitude larger than those for electricity. Second, closing urban nutrient cycles will require transport of nutrients from cities to surrounding cropland. Estimated transport distances across 56 of the world’s largest cities span two orders of magnitude and are often shorter among European, African, and Asian cities due to factors such as high local cropland density and nutrient-intensive crops. The energy requirements associated with transporting nutrients may constrain whether certain recovery strategies and products (e.g., reclaimed wastewater, sludge) are locally feasible. Finally, the agronomic value of nutrient application depends upon interactions between product chemistry and soil context. For example, alkaline products (e.g., struvite) may be particularly beneficial when applied to acidic soils in Uganda but potentially detrimental in the southwestern United States. The final two objectives reflect the need to develop broadly applicable conceptual frameworks that enumerate possibilities and support holistic and contextual assessment of sanitation options. The first framework characterizes links between resource recovery from sanitation and ecosystem services to shed light on the viability of exploring synergistic interactions between engineered and natural systems. Bridging these fields may create opportunities to support goals related to climate regulation, soil conservation, and water quality, among others. A spatial analysis further demonstrates resource recovery’s potential to contribute to distinct regional ecosystems across the globe. The second framework envisions sanitation as a distinct category of social-ecological system centered on human-derived resources (e.g., nutrients, energy), functioning within an overarching structure of social, economic, and environmental settings. Multiple layers of variables are identified and placed in the framework structure, which is applied to assess alternative sanitation scenarios in a specific context (Bwaise, Uganda) to reveal multi-dimensional tradeoffs and the impacts of individual processes on system outcomes. Overall, this work suggests that resource recovery from sanitation can create numerous opportunities to amplify sustainable development, but a number of local and global issues affect the feasibility and potential impact of various recovery and reuse strategies. Moving forward, integrating the analyses and frameworks developed here and implementing them across various settings can support understanding and decision-making around sanitation and resource recovery to design successful systems and promote a more sustainable future.LimitedAuthor requested closed access (OA after 2yrs) in Vireo ETD syste