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

Daniel Ddiba,Arno Rosemarin,Helfrid Schulte-Herbrüggen,Kim Andersson,Sarah Dickin

doi:10.1007/s10668-021-01487-w

Abstract

There is growing recognition of the potential environmental and socio-economic benefits of applying a circular 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, studies assessing circular economy potential have so-far been conducted mostly in high-income countries, yet cities in low- and middle-income countries have different challenges when developing a circular economy. This paper addresses this gap by estimating the resource recovery potential of organic waste streams in the context of low- and middle-income countries, illustrated with the case of 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 and revenues from the products could range from 5.1 million USD from compost to 47 million USD from biogas. The results demonstrate how complex information describing urban waste 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.

Highlights

Over half of the world’s population lives in cities and this proportion is expected to increase to two-thirds by 2050, with 90% of the increase occurring in low- and middleincome countries (UN DESA, 2018)
Comparing between resource recovery options, the quantity of nutrients that can be recovered from digestate and from composting seems similar, while a much lower quantity of nutrients can be recovered from the residue of black soldier fly (BSF) processing
The relatively higher potential revenues from anaerobic digestion of OMSW could be explained by the higher biomethane potential and volatile solids content of the OMSW in comparison with the faecal sludge (FS) and sewage sludge (SS) which lead to Volatile solids degradation rate, VSD Dry mass reduction rate for anaerobic digestion (AD) residue, DMRAD Biomass conversion rate for black soldier fly (BSF) larvae, bioconversion rate (BCR) Dry mass reduction rate for BSF residue, DMRBSF Total nitrogen (TN) reduction in BSF residue, TNRBSF Total phosphorus (TP) reduction in BSF residue, TPRBSF Total potassium (TK) reduction in BSF residue, TKRBSF Dry mass reduction in compost, DMRC Total nitrogen (TN) reduction during composting, TNRC Total phosphorus (TP) reduction during composting, TPRC Total potassium (TK) reduction during composting, TKRC Sewage sludge

Summary

Introduction

Over half of the world’s population lives in cities and this proportion is expected to increase to two-thirds by 2050, with 90% of the increase occurring in low- and middleincome countries (UN DESA, 2018). Over 700 million people in urban areas in low- and middle-income countries still lack access to improved sanitation facilities (WHO and UNICEF, 2017). They rely on unsanitary solid waste management systems, e.g. open dumpsites (Kaza et al, 2018).

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Conclusion