Willingness among food consumers to recycle human urine as crop fertiliser: Evidence from a multinational survey

Supply, demand and the economic effectiveness of urine-diverting technologies and products: A systematic literature review

The broader adoption of urine-diverting technologies (UDTs) and related products has been proposed as a strategy for moving towards a more circular economy. While some studies have explored the performance of UDTs, the interconnected factors involving supply, demand, and economic feasibility of UDTs remain under-researched. Our systematic review addresses this gap. Our search identified only 64 relevant, peer-reviewed studies, 71 % of which addressed the supply side (primarily the technical aspect of UDTs) and 58 % of which addressed the demand side (focusing on consumers' perceptions). Approximately one-third (18) of these studies delved into the economic feasibility of UDTs, with only 9 employing a cost benefit analysis (CBA) framework. However, none of these studies have analysed the economic performance of UDTs that have been fully deployed, indicating a significant knowledge gap. Our review suggests that overcoming challenges in scaling up UDTs can be achieved by engaging those stakeholders driving the uptake, developing business cases that offer an overall understanding of both market and non-market benefits of UDTs, addressing technological constraints by optimising urine treatment options for efficiency and economic viability, and enhancing stakeholders' acceptance of UDTs.

Legitimacy of source-separating wastewater systems with Swedish water utilities

Nutrient management is one of the critical challenges for developing sustainable circular economies in cities. Nutrients such as nitrogen and phosphorus from our food end up in our wastewater and pose an environmental threat when they are released in waterways. Yet, these nutrients are essential for crop production and food security. Hince human excreta contains the bulk of nutrients going through the urban ecosystem. Source separation of excreta from the rest of urban wastewater flows can enable safe and efficient nutrient recovery. Yet, source-separating wastewater systems are not yet common in urban areas. The aim of this study is to assess the legitimacy of source-separating wastewater systems from the perspective of wastewater professionals in Sweden. The study uses interviews and a survey to explore the pragmatic, normative, cognitive and regulatory dimensions of legitimacy and how these aspects can vary between different municipalities. Finally, it looks into possible knowledge-based activities to increase legitimacy. The results from this study show variations in legitimacy levels in urban areas in Sweden. Overall opinion appears to be neutral to the concept rather than negative. Although many see multiple barriers to implementation. Normative legitimacy (moral motivation) was relatively high, while cognitive legitimacy (knowledge & experiences) was lowest. Respondents from organizations where source-separation is being implemented, or they believe that it will be implemented within 10 years, generally saw more drivers and fewer barriers. These innovators were also more interested in knowledge-based activities. Overall recommendations to increase cognitive knowledge regarding source-separating systems among multiple stakeholders seems the most promising path forward to increase legitimacy in the Swedish wastewater sector.

Excreta Disgust and Adaptive Use of Ecological Sanitation By-Products: Perspectives of Rural Farmers in Burera District, Rwanda

Ecological sanitation (Ecosan) by-products are inherently limited in their potential use as excreta resources. Disgust behind human excreta and derivatives continues to challenge the further use of Ecosan-by products. Although treated excreta, including Ecosan by-products, have gradually been adopted worldwide, diverse perspectives among users hinder their use in agro-practices. This study explored perceptions of the use of Ecosan-by products as relates to the disgust of human excreta among rural farmers in Burera district, Rwanda. A qualitative study was conducted amongst three farmers' cooperatives using Ecosan by-products. We conducted six focus group discussions (FDGs) comprising a total of 48 participants taking into account the following three themes: core excreta disgust, perceived waste, and perceived resource. Thematic analysis was conducted with similar perspectives identified and grouped under emerging sub-themes. The perspectives regarding disgust elicitors included stigma, eversion, phobia, taboos, and health risks. Ecosan by-products were largely perceived as useful, with most farmers trusting and willing to touch the by-products. Psychosocial barriers to using the by-products continued to slow down the adoption of Ecosan for agricultural options. There is a need for increased awareness to scale up the use of Ecosan coupled with effective treatment practices for the products so as to reverse the psychological barriers resulting from traditional excreta disgust over Ecosan-products of faeces and urine.

Overflow Control for Sustainable Development by Superwetting Surface with Biomimetic Structure

Liquid flowing around a solid edge, i.e., overflow, is a commonly observed flow behavior. Recent research into surface wetting properties and microstructure-controlled overflow behavior has attracted much attention. Achieving controllable macroscale liquid dynamics by manipulating the micro-nanoscale liquid overflow has stimulated diverse scientific interest and fostered widespread use in practical applications. In this review, we outline the evolution of overflow and present a critical survey of the mechanism of surface wetting properties and microstructure-controlled liquid overflow in multilength scales ranging from centimeter to micro and even nanoscale. We summarize the latest progress in utilizing the mechanisms to manipulate liquid overflow and achieve macroscale liquid dynamics and in emerging applications to manipulate overflow for sustainable development in various fields, along with challenges and perspectives.

Sensor-based evaluation of a Urine Trap toilet in a shared bathroom

Urine diversion in a No-Mix Toilet is a promising approach for sustainable fertilizers and reduction of the nutrient load for wastewater treatment; however, user adoption remains a challenge. This study evaluates the Urine Trap, a passive No-Mix toilet design based on the teapot effect, wherein the urine stream inlet is invisible to the user and therefore it does not impact the user experience for increased adoption. This study evaluated the nutrient separation performance of a Urine Trap flush toilet in a bathroom shared by women in two sites in India. Over three different testing periods, 841 uses of this squat plate were recorded in 50 days. Analytical measurements found 36 % separation efficiency for total nitrogen (TN). While effective, the Urine Trap under test by users did not yield a 70-80 % TN separation efficiency observed under engineering characterization. High temporal resolution data from sensors on waste collection tanks, the opening of the bathroom door, and cleansing water flow were used to gain insights into hygiene practices. The data showed a frequent habit of wetting the squat plate during physiological excretion, a hygienic practice that eases cleaning but degrades the teapot separation effect of the Urine Trap design. By using sensors, we demonstrate a method to non-invasively gain quantitative insights into hygiene practices to inform sanitation technologies deployment strategies for improved outcomes.

The potential of composting toilets in addressing the challenges of faecal sludge management in community-led total sanitation (CLTS)

Community-led total sanitation (CLTS) is increasingly promoted globally as an innovative approach to addressing the sanitation challenge in developing countries, especially in the rural areas where access to sanitation remains poor. However, a significant challenge in CLTS is poor management of faecal sludge when pits are full. In this regard, composting toilets offer a potentially viable and ecologically sound method for effective and efficient faecal sludge management, by providing fertilisers that act as soil conditioners, and ultimately contribute to clean environment, food security, good health, and poverty alleviation. Despite these advantages, there is limited knowledge on why and how composting toilets can be successfully integrated into CLTS initiatives. In this paper, we use the case of Ghana to demonstrate that integrating composting toilets into the CLTS approach is a feasible option for sustainable and environmentally friendly faecal sludge management in rural areas where agriculture is the predominant livelihood activity.

Behavioral intentions of rural farmers to recycle human excreta in agriculture

Considerable progress has been made in developing human excreta recovery pathways and processes for maximum nutrient recovery and contaminant elimination. The demand segment has often been ignored as an area for future research, especially during the technology development. The findings from the few published articles on social acceptance show missing and inconclusive influence of demographic, sociological, and economic farmer-characteristics. This study endeavours to close this gap by using the social psychological theories, technology adoption theories and the new ecological paradigm to investigate the factors that influence the behavioral intentions of rural farmers to recycle human excreta in agriculture. Study findings show that social acceptance was driven by awareness, religiosity, income, source of income, and environmental dispositions. Perceived behavioral control represents a potential barrier to human excreta reuse. The study recommends the demographic, cultural, sociological, and economic mainstreaming of dissemination strategies of circular bioeconomy approaches within the context of agricultural innovation systems.

Removal of diclofenac and oxytetracycline from synthetic urine by furfuryl alcohol-derived mesoporous carbon

In this study, using furfuryl alcohol as the precursor carbon and mesoporous silica as the template, and furfuryl alcohol-derived mesoporous carbon (FMC) was prepared. The specific surface area of FMC was 1022.61 m²/g, the pore volume was 1.71 cm³/g, and the mesoporous volume was 98.8%. Based on the adsorption kinetics of pharmaceuticals onto the FMC in synthetic urine, equilibrium adsorption was reached in 120 min, and it followed a pseudo-second-order model. The adsorption isotherms were well-fitted by the Sips isotherm model, and the saturated adsorption capacities of diclofenac and oxytetracycline in fresh urine were 411.8 mg/g and 465.9 mg/g, respectively. Batch experiment results showed that pharmaceutical removal was strongly influenced by urine components such as sodium chloride, urea, and ammonium hydroxide. The adsorption of diclofenac and oxytetracycline was influenced by many factors including π-π interactions, hydrogen bonds, and electrostatic forces. FMC exhibited excellent reusability and retained urine nutrients during pharmaceutical adsorption.

Poor awareness and attitudes to sanitation servicing can impede China's Rural Toilet Revolution: Evidence from Western China

The ongoing Toilet Revolution in China offers an opportunity to improve sanitation in rural areas by introducing new approaches, such as urine source separation, that can contribute to achieving SDG6. However, few studies have systematically assessed the social acceptability of managing human excreta collected in new sanitation systems. Therefore, in this study we performed face-to-face interviews with 414 local residents from 13 villages across three provinces in western China, to analyze the current situation and attitudes to possible changes in the rural sanitation service chain. We found that the sanitation chain was predominantly pit latrine-based, with 86.2% of households surveyed collecting their excreta in a simple pit, 82% manually emptying their pits, and 80.2% reusing excreta in agriculture without adequate pre-treatment. A majority (72%) of the households had a generally positive attitude to production of human excreta-derived fertilizer, but only 24% agreed that urine and feces should be collected separately. Multivariate logistic regression indicated that three factors (level of education, number of permanent household residents, perceived social acceptability) significantly influenced respondents' attitudes to reuse of excreta, although only perceived social acceptability had a high strength of association. Overall, our survey revealed that rural households often misuse toilet systems, fail to comply with government-specified sanitation guidelines, have low awareness of alternative solutions, and are over-reliant on the government to fix problems in the service chain. Thus while new sanitation technologies should be developed and implemented, information campaigns that encourage rural households to manage their excreta safely are also important.

Attitudes of food consumers at universities towards recycling human urine as crop fertiliser: A multinational survey dataset

We present here a data set generated from a multinational survey on opinions of university community members on the prospect of consuming food grown with human urine as fertiliser and about their urine recycling perceptions in general. The data set comprises answers from 3,763 university community members (students, faculty/researchers, and staff) from 20 universities in 16 countries and includes demographic variables (age bracket, gender, type of settlement of origin, academic discipline, and role in the university). Questions were designed based on Ajzen's theory of planned behaviour to elicit information about three components of behavioural intention-attitudes, subjective norms, and perceived behavioural control. Survey questions covered perceived risks and benefits (attitudes), perceptions of colleagues (injunctive social norm) and willingness to consume food grown with cow urine/faeces (descriptive social norm), and willingness to pay a price premium for food grown with human urine as fertiliser (perceived behavioural control). We also included a question about acceptable urine recycling and disposal options and assessed general environmental outlook via the 15-item revised New Ecological Paradigm (NEP) scale. Data were collected through a standardised survey instrument translated into the relevant languages and then administered via an online form. Invitations to the survey were sent by email to university mailing lists or to a systematic sample of the university directory. Only a few studies on attitudes towards using human urine as fertiliser have been conducted previously. The data described here, which we analysed in "Willingness among food consumers at universities to recycle human urine as crop fertiliser: Evidence from a multinational survey" [1], may be used to further understand potential barriers to acceptance of new sanitation systems based on wastewater source separation and urine recycling and can help inform the design of future sociological studies.