The public subsidy trap: a systematic review of systemic failures in municipal solid waste public-private partnerships (PPP)

Public-private partnerships (PPPs) are widely promoted to improve municipal solid waste management (MSWM), especially in developing and emerging economies. However, many MSW PPPs continue to underperform despite formal contracts, private-sector involvement, and public oversight. This study examines why these failures persist by systematically reviewing 33 empirical studies on MSW PPPs. Using PRISMA-guided study selection, thematic coding, semi-quantitative scoring, and system dynamics modelling, the review analyses how institutional capacity, financial cost recovery, contract duration, and technology complexity interact to shape PPP performance. The findings show that many MSW PPPs remain locked in a low-level equilibrium, where partnerships focus mainly on labour-intensive collection and disposal rather than progressing toward resource recovery or circular economy outcomes. The main novelty of this study is the identification of the “public subsidy trap”: a systemic condition in which stronger monitoring does not improve performance when financial cost recovery remains weak. Instead, oversight increases administrative burden while continued subsidies drain public budgets. Quantitative benchmarking further indicates that cost recovery is positively associated with service performance, although governance quality, public trust, contract design, and technical capacity also influence outcomes. The study argues that developing economies should avoid premature investment in capital-intensive waste technologies without first securing institutional and financial foundations. A phased pathway is proposed: strengthen monitoring and enforcement, improve financial transparency and cost recovery, and then invest in advanced treatment or resource recovery technologies.