The Impact of Pro-Poor Sanitation Subsidies in Open Defecation-Free Communities: A Randomized, Controlled Trial in Rural Ghana.

BACKGROUND: According to the World Health Organization/United Nations International Children's Fund Joint Monitoring Program, 494 million people practice open defecation globally. After achieving open defecation-free (ODF) status through efforts such as Community-Led Total Sanitation (CLTS), communities (particularly vulnerable households) may revert to open defecation, especially when toilet collapse is common and durable toilets are unaffordable. Accordingly, there is increasing interest in pro-poor sanitation subsidies. OBJECTIVES: This study determined the impacts of a pro-poor sanitation subsidy program on sanitation conditions among the most vulnerable households and others in the community. METHODS: In 109 post-ODF communities in Northern Ghana, we conducted a cluster randomized controlled trial to evaluate a pro-poor subsidy program that identified the most vulnerable households through community consultation to receive vouchers for durable toilet substructures. We surveyed households to assess toilet coverage, quality, and use before and after the intervention and tracked program costs. RESULTS: Overall, sanitation conditions deteriorated substantially from baseline to endline (average of 21 months). In control communities (not receiving the pro-poor subsidy), open defecation increased from 25% (baseline) to 69% (endline). The subsidy intervention attenuated this deterioration (open defecation increased from 25% to only 54% in subsidy communities), with the greatest impacts among voucher-eligible households. Noneligible households in compounds with subsidized toilets also exhibited lower open defecation levels owing to in-compound sharing (common in this context). CLTS followed by the subsidy program would benefit more households than CLTS alone but would cost 21-37% more per household that no longer practiced open defecation or upgraded to a durable toilet. DISCUSSION: Sanitation declines, often due to toilet collapse, suggest a need for approaches beyond CLTS alone. This subsidy program attenuated declines, but durable toilets likely remained unaffordable for noneligible households. Targeting criteria more closely aligned with sanitation inequities, such as household heads who are female or did not complete primary education, may help to generate greater and more sustainable impacts in Northern Ghana and, potentially, other contexts facing toilet collapse and limited market access. https://doi.org/10.1289/EHP10443.

Defining Nutrient Colocation Typologies for Human-Derived Supply and Crop Demand To Advance Resource Recovery.

Resource recovery from human excreta can advance circular economies while improving access to sanitation and renewable agricultural inputs. While national projections of nutrient recovery potential provide motivation for resource recovery sanitation, elucidating generalizable strategies for sustainable implementation requires a deeper understanding of country-specific overlap between supply and demand. For 107 countries, we analyze the colocation of human-derived nutrients (in urine) and crop demands for nitrogen, phosphorus, and potassium. To characterize colocation patterns, we fit data for each country to a generalized logistic function. Using fitted logistic curve parameters, three typologies were identified: (i) dislocated nutrient supply and demand resulting from high density agriculture (with low population density) and nutrient islands (e.g., dense cities) motivating nutrient concentration and transport; (ii) colocated nutrient supply and demand enabling local reuse; and (iii) diverse nutrient supply-demand proximities, with countries spanning the continuum between (i) and (ii). Finally, we explored connections between these typologies and country-specific contextual characteristics via principal component analysis and found that the Human Development Index was clustered by typology. By providing a generalizable, quantitative framework for characterizing the colocation of human-derived nutrient supply and agricultural nutrient demand, these typologies can advance resource recovery by informing resource management strategies, policy, and investment.

Navigating Data Uncertainty and Modeling Assumptions in Quantitative Microbial Risk Assessment in an Informal Settlement in Kampala, Uganda.

Decision-makers in developing communities often lack credible data to inform decisions related to water, sanitation, and hygiene. Quantitative microbial risk assessment (QMRA), which quantifies pathogen-related health risks across exposure routes, can be informative; however, the utility of QMRA for decision-making is often undermined by data gaps. This work integrates QMRA, uncertainty and sensitivity analyses, and household surveys in Bwaise, Kampala (Uganda) to characterize the implications of censored data management, identify sources of uncertainty, and incorporate risk perceptions to improve the suitability of QMRA for informal settlements or similar settings. In Bwaise, drinking water, hand rinse, and soil samples were collected from 45 households and supplemented with data from 844 surveys. Quantified pathogen (adenovirus, Campylobacter jejuni, and Shigella spp./EIEC) concentrations were used with QMRA to model infection risks from exposure through drinking water, hand-to-mouth contact, and soil ingestion. Health risks were most sensitive to pathogen data, hand-to-mouth contact frequency, and dose-response models (particularly C. jejuni). When managing censored data, results from upper limits of detection, half of limits of detection, and uniform distributions returned similar results, which deviated from lower limits of detection and maximum likelihood estimation imputation approaches. Finally, risk perceptions (e.g., it is unsafe to drink directly from a water source) were identified to inform risk management.

Re-Envisioning Sanitation As a Human-Derived Resource System.

Sanitation remains a global challenge, both in terms of access to toilet facilities and resource intensity (e.g., energy consumption) of waste treatment. Overcoming barriers to universal sanitation coverage and sustainable resource management requires approaches that manage bodily excreta within coupled human and natural systems. In recent years, numerous analytical methods have been developed to understand cross-disciplinary constraints, opportunities, and trade-offs around sanitation and resource recovery. However, without a shared language or conceptual framework, efforts from individual disciplines or geographic contexts may remain isolated, preventing the accumulation of generalized knowledge. Here, we develop a version of the social-ecological systems framework modified for the specific characteristics of bodily excreta. This framework offers a shared vision for sanitation as a human-derived resource system, where people are part of the resource cycle. Through sanitation technologies and management strategies, resources including water, organics, and nutrients accumulate, transform, and impact human experiences and natural environments. Within the framework, we establish a multitiered lexicon of variables, characterized by breadth and depth, to support harmonized understanding and development of models and analytical approaches. This framework's refinement and use will guide interdisciplinary study around sanitation to identify guiding principles for sanitation that advance sustainable development at the nature-society interface.

Navigating Multidimensional Social-Ecological System Trade-Offs across Sanitation Alternatives in an Urban Informal Settlement.

Urban growth in low- and middle-income countries has intensified the need to expand sanitation infrastructure, especially in informal settlements. Sanitation approaches for these settings remain understudied, particularly regarding multidimensional social-ecological outcomes. Guided by a conceptual framework (developed in parallel with this study) re-envisioning sanitation as a human-derived resource system, here we characterize existing and alternative sanitation scenarios in an informal settlement in Kampala, Uganda. Combining two core research approaches (household survey analysis, process modeling), we elucidate factors associated with user satisfaction and evaluate each scenario's resource recovery potential, economic implications, and environmental impacts. We find that existing user satisfaction is associated with factors including cleaning frequency, sharing, and type of toilets, and we demonstrate that alternative sanitation systems may offer multidimensional improvements over existing latrines, drying beds, and lagoons. Transitioning to anaerobic treatment could recover energy while reducing overall net costs by 26-65% and greenhouse gas emissions by 38-59%. Alternatively, replacing pit latrines with container-based facilities greatly improves recovery potential in most cases (e.g., a 2- to 4-fold increase for nitrogen) and reduces emissions by 46-79%, although costs increase. Overall, this work illustrates how our conceptual framework can guide empirical research, offering insight into sanitation for informal settlements and more sustainable resource systems.

Advancing Sustainable Sanitation and Agriculture through Investments in Human-Derived Nutrient Systems.

The sixth Sustainable Development Goal seeks to achieve universal sanitation, but a lack of progress due to inhibiting factors (e.g., limitations in financial resources, sociocultural conditions, household decision-making) demands innovative approaches to meet this ambitious goal. Resource recovery may generate income to offset sanitation costs while also enhancing agriculture through increased access to agricultural nutrients. The objective of this work was to determine if resource recovery sanitation can be a profitable business model in a specific context (Kampala, Uganda) and to explore the potential for this approach to translate to other Sub-Saharan African contexts. A techno-economic analysis was performed to evaluate the financial viability of two nutrient recovery systems and business models in urban communities in Kampala under two financing scenarios: (1) Startup relying on partial sanitation aid, and (2) Self-sustaining without philanthropic financing. Results show profitability can be achieved at a nutrient selling price at or below fertilizer market value in Uganda. Recoverable nutrients from the total population without at least basic sanitation services, in 10 Sub-Saharan African countries, are the same magnitude as nutrients distributed in subsidy programs (30-450% of distributed nutrients), indicating a potential to offset inorganic fertilizer consumption or increase nutrient availability. This research makes a case to support innovative sanitation strategies and the development and financial support of human-derived fertilizer markets in areas with poor fertilizer and sanitation access.

Aligning Product Chemistry and Soil Context for Agronomic Reuse of Human-Derived Resources.

Recovering human-derived nutrients from sanitation systems can offset inorganic fertilizer use and improve access to agricultural nutrients in resource-limited settings, but the agronomic value of recovered products depends upon product chemistry and soil context. Products may exacerbate already-compromised soil conditions, offer benefits beyond nutrients, or have reduced efficacy depending on soil characteristics. Using global spatial modeling, we evaluate the soil suitability of seven products (wastewater, sludge, compost, urine, ammonium sulfate, ammonium struvite, potassium struvite) and integrate this information with local recovery potential of each product from sanitation systems that will need to be installed to achieve universal coverage (referred to here as "newly-installed sanitation"). If product recovery and reuse are colocated, the quantity and suitability of nutrient reuse was variable across countries. 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. Further, we illustrate discrepancies across soil data sets and highlight the need for locally accurate data, knowledge, and interpretation. Overall, this study demonstrates soil context is critical to comprehensively characterize the value proposition of nutrient recovery, and it provides a foundation for incorporating soil suitability into local and global sanitation decision-making.

Child soil ingestion in rural Ghana - frequency, caregiver perceptions, relationship with household floor material and associations with child diarrhoea.

OBJECTIVES: The objectives of this work were to evaluate (i) the prevalence and frequency of caregiver-reported soil ingestion by children, (ii) whether household flooring material in the bedroom (earth vs. concrete) affected caregiver-reported soil ingestion, (iii) whether caregiver-reported soil ingestion was associated with caregiver-reported diarrhoea and (iv) caregivers' perceptions of their children ingesting soil. METHODS: We conducted 309 household surveys in northern Ghana, including 529 children under five (249 children aged 6-36 months), and measured faecal contamination in soil from 31 households. RESULTS: Among all children, 15% were reported to have directly ingested soil in the past week, including 28% of children aged 6-36 months. Among children reported to have ingested soil, the median frequency was 14 times in the past week, and the median amount of soil ingested each time was half a handful. There was no association between household floor material and whether the caregiver observed a child directly ingesting soil. After adjusting for household floor material and other potential confounding variables, caregiver-reported soil ingestion was associated with caregiver-reported diarrhoea for children under five [adjusted odds ratio (adj. OR) = 3.13, 95% confidence interval (CI) 2.76-3.55] and children aged 6-36 months (adj. OR = 2.61, 95% CI 2.01-3.39). Approximately 83% of caregivers whose children ingested soil reported they thought it was unsafe and were more likely to report stopping their child from ingesting soil, but these responses did not affect the quantity of soil ingested. CONCLUSIONS: Our results suggest direct soil ingestion is associated with diarrhoea independent of household floor material, and separate interventions may be necessary to prevent exploratory soil ingestion.

Amplifying Progress toward Multiple Development Goals through Resource Recovery from Sanitation.

The United Nations' Sustainable Development Goals (SDGs) recognize that current sanitation gaps must be closed to better serve those without access to safely managed systems (Target 6.2: universal sanitation coverage) and those connected to sewers without wastewater treatment (Target 6.3: halving the proportion of untreated wastewater). Beyond mitigating environmental and health concerns, implementing resource recovery sanitation systems could simultaneously improve the availability of agricultural nutrients (SDG 2) and household energy (SDG 7). This study estimates the potential for global, regional, and country-level resource recovery to impact nutrient and household electricity use through 2030. We distinguish impacts from newly installed sanitation systems (to achieve universal coverage), newly treated wastewater systems (to halve the proportion of untreated wastewater), and existing system replacement, while also considering urban and rural disparities and spatial colocation of nutrients with agricultural needs. This work points toward country-specific strategies for deriving the greatest benefit from sanitation investments while also identifying overarching trends to guide international research efforts. Globally, potential nutrient gains are an order of magnitude larger than electricity (a small fraction of total energy), and considerable impacts are possible in the least-developed countries, six of which could double or offset all projected nutrient and electricity use through newly installed sanitation systems.