Towards a circular transition of the built environment: systemic and transdisciplinary models, methods and perspectives

The urgency of a transition to sustainable models of production and consumption is one of the most pressing challenges of our times. Among various models proposed, a transition to a circular economy offers workable solutions to catalyse developing and improving sustainability frameworks from material and system perspectives. In a nutshell, circular economy is defined as an industrial system which aims to gradually decouple economic growth from the consumption of finite resources through enhancing resource efficiency and designing waste out of systems (Ellen MacArthur Foundation). Having been dominated by a linear economic model (take-make-dispose) since the industrial revolution, the built environment is one of the world’s largest consumer of resources, a major producer of waste and a major culprit behind increasing CO2 emissions. Various industry reports already point out to the ample opportunities for businesses, governments, and cities through the adoption of circular economy approaches. These opportunities are similarly portable to a resource-intensive and high waste sector like the built environment. The built environment constitutes human-made buildings, built assets, and facilities viewed collectively as an environment in which we live and work. It is a highly complex social, ecological, and technical system that can be defined in various scales and levels – buildings, building stocks, neighbourhoods, cities, and regions – each with different time constants, actors and institutional regimes (McGrath & Lei, 2021). The built environment is also defined as an artefact in the overlapping zone between culture and nature, with causation occurring in both directions (Hassler & Kohler, 2014). This begs several questions, such as: what exactly circular economy can mean and imply for the built environment? How can we drive and implement its transition into a system which is regenerative by design? And an equally important question is how can we reconnect it to the broader natural and social systems that are fundamental to maintain it? Although the field has observed a growing awareness in recent years, there is no explicit formula as to how to develop, finance, procure, design, construct, operate, maintain, and repurpose services and assets to enable the desired transition. The now available literature has been concerned mostly with the ‘why’ and ‘what’ questions related to a circular transition for the built environment, whereas, the ‘how’ questions have received scant attention. Designing new biodegradable materials, or new building systems that can be dismantled and easily remanufactured into new products will not create a successful transition at the required level. That is because we currently do not have buy-in from key players and lack the supply chains and business models in place to close the material loops. In this regard, a circular built environment will not materialize through point solutions that target the collection of reused, recycled materials or re-manufactured building components. In essence, circularity is the property of a system and how a system handles its materials and product flows with minimum waste and with maximum value gains. Regardless of whether we are dealing at material scale, or a building or a neighbourhood scale; we can only gain circular value through the system’s ability to keep its flows in a closed loop. Therefore, we also need to design a system with aligned interests of all supply chain actors and with various levels of public, private, and social interventions. A circular transition, therefore, should be informed by System Thinking, which requires the ability to understand how different parts interact to shape the behaviour of the system as a whole. A systemic change requires all relevant system actors on board, fundamental changes in industrial ecosystems