the World Bank, the International Monetary Fund, and regional for as long as possible, thus extending their life cycle. Many development banks) support these trends via legal support analysts expect that the introduction of circular economy and loans. Fourth, infrastructure development is becoming models will reduce waste to a minimum. If a product reaches more and more complex, because most projects are being the end of its life, its components and materials should be kept undertaken in existing urban environments that already host within the economy wherever possible. Because this circular old infrastructure. model relies on large quantities of cheap, easily accessible materials and energy, many anticipate it will create further The rise of individual megaprojects raises two issues. City value. We observe that the sharing economy model is being authorities have to deal with extremely complex contracts adopted across the world at a sustained pace. However, it will governing the planning, construction, and operations of the take a long time to fundamentally change both manufacturing infrastructure that will be developed. Furthermore, specific and economic structures and influence customers’ purchasing institutional mechanisms are required to manage public-private behaviors. partnerships: changes to service requirements, changes to tariff formulae, and cost adjustments enacted in response to It is important for city managers and planners to understand market changes. how circular economy initiatives can strengthen ties with the sharing economy and how these two initiatives can be Ultimately, these new public-private partnerships and their successfully integrated. Consequently, we need to better financing instruments largely benefit the private sector, which understand what would result from this integrative approach at accrues the bulk of the returns on investment. In some cases, the company level—that is, its implications in terms of business the creation of some social value or contribution to the common models. good is hidden or missed. Do they show superior returns on finance capital compared to other types of capital? For a Finally, urban transformation could favor the implementation multitrillion dollar private sector market for infrastructure of new sustainable principles and facilitate the implementation projects to be viable,54infrastructure investments will have to of sharing models such as ride sharing, car sharing, and home be both sustainable and equitable in their serving of the public sharing. Assigning multiple roles to new infrastructure would good. encourage an economy that embraces the concept of sharing. Some types of infrastructure (energy grids, distributed networks The Circular and Sharing Economies. Urban transformation for caring, and remote assistance to the elderly) can contribute highlights the connection between the circular economy and to greater social equity and better inclusiveness. the sharing economy. We know that our previous patterns of consumption and production are no longer sufficiently Financing for Sustainable Infrastructure. Infrastructure sustainable, because they are overly reliant on the extraction is paramount to all of a city’s actors and stakeholders. of nonrenewable resources (such as fossil energies or scarce Infrastructure is developed and operated most effectively and raw materials). They are also heavily based on overusing efficiently when its stakeholders work in concert with one linear processes to manufacture goods and produce services. another. To make large cities more sustainable and resilient For example, the buildings industry is still a major consumer to climate change, it will be indispensable to elevate the of energy and resources. Across the overall value chain and quality, reliability, and capacity of urban infrastructure. New the entire life cycle of buildings (materials sourcing, design, kinds of infrastructure for new ways of living could lead to manufacturing, distribution, consumption, and disposal), sustainable urban transformation and new city environments. greenhouse gas (GHG) emissions will be generated.The aim is to reshape our way of thinking and thus potentially Unfortunately, we do not yet have the tools or instruments change institutions and mechanisms. Infrastructure is more required to effectively measure GHG emissions along the life than physical equipment used to sustain the economy. It cycle of a given piece of equipment, but we do know that using is dramatically important in emerging countries, where more wooden components in construction can reduce GHGs. addressing social needs is often being hampered by difficulties in building up critical infrastructure (for example, power, water The circular economy is a new model of production and pipes, and harbors) and providing key assets (for example, consumption that departs from the traditional take-make- housing and schools). An illustration of the long-term benefits consume-discard pattern. It has multiple facets. Generally of infrastructure is the way in which Medellín’s Metrocable speaking, it involves recycling existing materials and products system has transformed for the better the ability of people in (54) Fay, M., Han, S., Lee, H. I., Mastruzzi, M., & Cho, M. (2019). Hitting the trillion mark: a look at how much countries are spending on infrastructure.The World Bank 44 Quélin and Smadja | HEC PARIS | SMART CITIES | The sustainable program of six leading cities | 2021