The article develops an integrated framework for incorporating informal resource flows into urban-metabolism analysis. It responds to the exclusion of informal actors and activities from official accounts, which can underestimate circular practices while obscuring vulnerability and unequal access to essential services.

The framework covers water, energy, waste, food and mobility and links flow analysis to actor typologies, governance and land use. It identifies flexible regulation, affordability, gender, participation and justice as cross-cutting dimensions. This allows informal systems to be differentiated according to their social and environmental functions rather than treated as a homogeneous residual category.

The contribution opens a pathway toward circular-economy policy that recognises informal knowledge and labour without romanticising precarity. It is central to the Lab’s postdoctoral research on informality in Brussels and Wallonia.