Estimating the potential for resource recovery from productive sanitation in urban areas.

To-date, sanitation has mainly been approached from a public and environmental health perspective and this implies that excreta and other organic waste streams are seen not only as a hazard to quickly get rid of but also as a very costly menace to manage. However, looking at sanitation management from a resource recovery perspective provides an avenue for solutions with multiple co-benefits. Revenues from sanitation end-use products can act as an incentive for improving sanitation infrastructure while also covering part or all of the investment and operation costs for the same. Until now, estimating the potential for resource recovery from sanitation systems and technologies has largely been done on a case by case basis according to project or geography with no standardized universal tools or methodologies being used across the world. This study is aimed at developing a generic model for the rapid estimation of the quantities of various resources that can be recovered from sanitary waste streams in urban areas. Key waste streams from sanitation systems in low and middle income countries were identified and their major characterization parameters identified. The mathematical relationships between key waste stream characterization parameters and the potential amounts of resource products derived from treatment were determined and then used to develop the model in MS Excel. The model was then tested with waste stream flow rates and characterization data (for faecal sludge, sewage sludge and organic municipal solid waste) from the city of Kampala with two scenarios; the current collection amounts (390 m3 of faecal sludge, 66 tonnes of sewage sludge and 700 tonnes of organic solid waste) and the potential amounts with increased collection efficiency and coverage (900 m3 of faecal sludge, 282 tonnes of sewage sludge and 2199 tonnes of organic solid waste). The results were shared with Kampala city authorities to obtain feedback. The results showed that there is significant potential in utilizing the daily amounts of the three waste streams collected in Kampala. With increased collection coverage and efficiency, they could altogether yield; up to 361,200 Nm3 of biogas per day which could meet the daily energy needs of 824,000 people that are currently met by firewood. Alternatively, the three sources could produce, 752 tonnes of solid combustion fuel per day which could meet the daily energy needs of 1,108,700 people that are currently met by firewood. As a third alternative, the three sources could produce 198 tonnes of Black Soldier Fly prepupae per day which could substitute for 134 tonnes of dry fish per day currently used as animal feed ingredient and up to 909 tonnes of compost fertilizer per day which is enough to substitute two tonnes of urea that is currently used by farmers. The model thus proved to be a simple way to provide decision support by making rapid estimations of the potential for resource recovery in urban areas, without the burden of having to do full scale feasibility studies. It is expected that this model could be a useful complement to the excreta flow diagrams (SFDs) developed within the Sustainable Sanitation Alliance (SuSanA) and hence give a holistic picture of the potential of a closed loop approach to excreta and waste management in cities

The lack of social impact considerations in transitioning towards urban circular economies : a scoping review

Worldwide, cities are implementing circular economy (CE) strategies to reduce the resources they consume and their environmental impact. However, the evidence of the intended and unintended social consequences of the transition to “circular cities” is scattered. The lack of a coherent overview of the evidence on the subject can hinder effective decision-making in policy and practice. This study examines the extent to which the current literature addresses the social impacts that a transition to a CE produces in cities. We used a methodological approach related to systematic mapping to collate the evidence published over the past decade globally. The study finds that social impacts have rarely been considered in studies of circular cities, and where they have been discussed, the scope has been quite limited, only covering employment (mostly of informal sector workers) and governance practices. This scoping review highlights the need to further analyse and integrate social impact considerations into decision-making connected to transitions towards circular cities.QC 20211101</p

The circular economy potential of urban organic waste streams in low- and middle-income countries

There is growing recognition of the potential environmental and socio-economic benefits of applying a circular economy approach to urban organic waste management through resource recovery. Decisions around planning and implementing circular urban waste systems require estimates of the quantity of resources available in waste streams and their potential market value. However, most case-studies have so-far been conducted in high-income countries and cities in low- and middle-income countries have different challenges when developing a circular economy. The present paper explores these issues by estimating the potential for resource recovery from organic waste streams in the context of low- and middle-income countries, illustrated in Kampala, Uganda. A simplified material flow analysis approach is used to track the transformation of waste streams, namely; faecal sludge, sewage sludge and organic solid waste into the resource recovery products biogas, solid fuel, black soldier fly larvae and compost. Findings indicate that even at current rates of waste collection, the three waste streams combined could annually yield 135,000 tonnes of solid fuel or 39.6 million Nm3 of biogas or 15,000 tonnes of black soldier fly larvae or 108,000 tonnes of compost. Potential revenues from the products could range from 5.1 million USD for compost to 47 million USD for biogas, annually. This case study demonstrates how complex information describing urban waste in specific cities can be presented to facilitate decision-making and planning by stakeholders. By highlighting different resource recovery opportunities, application of this approach could provide an incentive for more sustainable urban sanitation and waste management systems.QC 20210531UrbanCircl

Methods to reliably estimate faecal sludge quantities and qualities for the design of treatment technologies and management solutions

Sanitation access in urban areas of low-income countries is provided through unstandardized onsite technologies containing accumulated faecal sludge. The demand for infrastructure to manage faecal sludge is increasing, however, no reliable method exists to estimate total accumulated quantities and qualities (Q&amp;Q) This proposed approach averages out complexities to estimate conditions at a centralized to semi-centralized scale required for management and treatment technology solutions, as opposed to previous approaches evaluating what happens in individual containments. Empirical data, demographic data, and questionnaires were used in Kampala, Uganda to estimate total faecal sludge accumulation in the city, resulting in 270 L/capâ\u88\u99year for pit latrines and 280 L/capâ\u88\u99year for septic tanks. Septic tank sludge was more dilute than pit latrine sludge, however, public toilet was not a distinguishing factor. Non-household sources of sludge represent a significant fraction of the total and have different characteristics than household-level sludge. Income level, water connection, black water only, solid waste, number of users, containment volume, emptying frequency, and truck size were predictors of sludge quality. Empirical relationships such as a COD:TS of 1.09 ± 0.56 could be used for more resource efficient sampling campaigns. Based on this approach, spatially available demographic, technical and environmental (SPA-DET) data and statistical relationships between parameters could be used to predict Q&amp;Q of faecal sludge.QC 20200511</p