Circular City initiatives in Europe are becoming increasingly popular. For example, Amsterdam, Paris and Berlin started their Circular City initiatives several years ago. Vienna, is launching a Circular City initiative in 2020. The Circular City movement is not limited to Europe. New York and Hong Kong are now using the Circular City concept as an organizing principle for policy and planning. This article, forthcoming on BDC scientific journal, makes the case that Circular City initiatives should place buildings at the top of Circular City agendas.
A circular economy approach to buildings is critically important to achieving the main goal of circularity, which is reducing the amount of natural resources and energy humans use. CE is not only about using less and recovering more, it also includes choosing sustainable low-carbon materials for construction, sharing spaces, and operating buildings in a low-carbon and resource efficient way. These are a few examples of how a circular perspective rethinks the ways in which we create buildings to provide shelter, health, and well-being today.
Circular city initiatives should focus first on buildings because the circular economy model, urban development, and buildings are inextricably linked. The link between circular economy, urban development and buildings is defined and driven by three simple facts of human settlements today: urbanization is increasing, resulting in intense unsustainable resource consumption; governance of urban environments reflects changing societal values toward the environment and sustainability; and buildings create urban form and function. A short overview of these drivers follows.
The circular economy concept is often presented as a potential solution to some of Europeans’ most pressing concerns, climate change, the environment, and energy issues, in general and specifically for cities. The perspective of circular economy as a way to achieve sustainability has entered the political and policy discourse through research, advocacy, and funding. A few recent examples of this phenomena are:
The Circular City movement is a new governance form that reflects today’s European values and concerns. Namely, the desire to be sustainable by addressing climate change, and reduce natural resources and energy use. The concerted policy, advocacy, and funding efforts have raised the profile of circular economy as a potentially effective governance strategy to achieve sustainability.
In summary, each unique urban tapestry, created by buildings, is and will continue to be a large share of the human ecological footprint. The Circular City challenge is to reduce the human ecological footprint, therefore a focus on buildings is crucial.
Having established why Circular City initiatives should focus on buildings above, this section discusses the opportunities in the buildings sector, focusing on existing and cultural heritage buildings. New construction is beyond the scope of the current article; however, the concepts discussed also apply to new construction. There are numerous circular economy strategies to reduce environmental impacts of individual existing building rehabilitations, including cultural heritage buildings. These occur at the micro-level and can mirror Circular City targets at the meso city-level. Certainly, opportunities span the range of sustainable community revitalization; but this article focuses only on the major environmental improvements possible due to rethinking buildings in a Circular City approach.
The four major environmental impacts of buildings that Circular City initiatives should target are:
Low-carbon development– As noted, one of the biggest environmental impacts of buildings is greenhouse gas emissions. Therefore, decarbonization of the building sector is a core goal of national and city plans to meet policy goals such as the Paris Agreement to limit global warming to 1.5o above pre-industrial levels. Decarbonization starts with buildings’ embodied carbon. Embodied carbon represents the energy used to provide for: the extraction and conversion of materials; transport to the building site; and construction into the building we see today. For example, according to the Inventory of Carbon and Energy Database, a standard Portland cement has average of Embodied Carbon (kgCO2e/kg), a general concrete averages 0.103 (kgCO2e/kg), and aluminium 6.67 (kgCO2e/kg). By reusing building components and parts replacing the materials is not necessary; therefore the embodied carbon is saved. One could think of this as the “replacement cost”. Another way to look at embodied carbon savings is to examine the embodied carbon of various building materials and chose the lowest embodied carbon materials that meet desired functions when designing a building. One could think of this as a “cost comparison” of materials. Retaining buildings and building materials and selecting low-carbon materials reduces the overall “carbon cost” of an adaptively reused building, thereby promoting low-carbon development in a Circular City framework.
Less construction and demolition (C&D) wastes– Reducing construction waste is a common goal of many cities. In Europe, C&D waste is the largest waste category. It is 25 – 30 percent of all waste. Managing large quantities of heavy waste is expensive and many cities find landfilling it challenging. This is the reason why the EU targets reducing C&D wastes in its Circular Economy Strategy and the 2018 EU Construction and Demolition Waste Protocol and Guidelines. Recycling of materials is encouraged by promoting improvements to, for example: Waste identification/separation and collection; logistics; and processing. A Circular City project can support the development of companies and jobs that make carrying out the mentioned improvements. In addition, a Circular City project can explicitly link the disposal & reuse phase of a buildings’ lifecycle to the materials sourcing and construction phases of other buildings.
Improving energy efficiency– An adaptive reuse of a cultural heritage building (ARCH) is an opportunity to upgrade the efficiency of windows, cooling and heating systems, insulation, roofing building envelopes, etc. These upgrades will make the building’s use of energy more efficient in its operations phase. Roughly two-thirds of residential energy consumption is for space and water heating/cooling. There is a dire need to increase building’s energy efficiency in general because there is currently an upward not downward trend in building’s energy use. According to the International Energy Agency, in 2018 buildings emitted 9.6 Gigatons CO2, which is an increase of 1.9 Gigatons since 2000. A Circular City perspective recognizes that increasing energy efficiency is not limited to new construction. By saving embodied energy of an ARCH and improving energy efficiency during use with upgrades to major systems mentioned above, the lifetime energy efficiency of an existing building may rival new construction. “Deep renovations” can reduce consumption by 30 – 50 percent. Significant energy efficiency gains leading to reductions in energy consumption can be targeted by a Circular City approach through organizing financing for energy efficiency investments with multiple routes including credits to utility bills. In addition, a Circular City may implement municipal procurement focused on existing and cultural heritage buildings.
Improving resource efficiency– Stated simply, resource efficiency is “doing more with less”. Meeting the growing human need for shelter (“doing more”) with “less” construction materials and energy. For example, “Relevant materials for the construction sector are: the metals iron, aluminium, copper, nickel, zinc and lead; the construction materials clay, sand and gravel, limestone, wood, and building stone”. Additionally, reducing fresh water consumption is also important. In the building sector, circular economy strategies that impact resource efficiency are carried out at different stages of the building life cycle and at various scales. For example, ARCH itself and the Design for Disassembly strategy at the design phase ultimately reduces material extraction.This can be done at the scale of a whole building and city. At the social / behavioral level, improving resource can be achieved at a micro scale during the operation phase, including through multiple uses of space, reducing floor space for residences, reducing water consumption, or sharing communal services such as laundries or outdoor recreation areas. Circular Cities can promote structural changes that improve resource efficiency at the building and city scale and social /behavioral adaptations at the micro scale.
Existing and historic buildings must be at the top of Circular City agendas. This article describes the motivations and justification for cities implementing or considering Circular City initiatives to focus on buildings. Circular City initiatives are a new and growing form of municipal governance. As cities plan to reduce their overall environmental footprints, emphasizing buildings is important because they are at the crossroads of urbanization, unsustainable resource consumption, and changing societal values towards sustainability.
Buildings define the spatial footprint, cultural footprint, and environmental footprint of the city. Fortunately, there are many opportunities for implementing circular strategies through municipal governance as noted in this article. Circular Cities should aim to achieve: low-carbon development; less construction and demolition wastes; improving energy efficiency; and improving resource efficiency in the buildings sector in line with European Union policy goals. There simply is no chance of planning a Circular City without existing and historic buildings.