Cities around the world represent not only the interaction of ecosystems, it also represents a space where different natural and also artificial processes occur. As a result of these processes and interactions, cities contain materials that unfortunately are discarded without being used despite the great value they represent for their own chain.
Currently, cities are emitters of approximately 40% of the total CO2 worldwide. Likewise, the construction and demolition waste consist of a major 5 segment of world production of waste and generation reached approximately 3 billion tons in 2012 across 40 countries. In Europe, the current percentage of Construction and Demolition waste represents the 25-30% of the total waste generated.
Under the circular economy approach these current wastes would become resources to be used. For this it is necessary to rethink processes and promote improvements from the design stage. By creating value and promoting a market that ensures the closing of the cycle in the construction sector. In the same way, increase of awareness of all sectors involved as well as society is necessary.
Challenges the cities are facing
Currently, factors such as demographics and climate are undergoing great changes. The population growth in cities experienced in recent years and the one that will not seem to stop until 2050 is called the second wave of population growth. For its part, the climate, due to the high levels of anthropogenic greenhouse gas emissions (GHG), is impacting locally and globally, threatening the survival of island or coastal nations, among other impacts. In this sense, cities are directly linked to both, since cities will host 68% of the world population by 2050 (UN DESA, 2018).
Promoting the circular economy approach in cities
The application of the circular economy approach in cities would help to solve many of the previously mentioned problems. Under this scenario, cities would reduce their CO2 emissions while meeting the demand for new urban areas. In a circular economy scenario, we seek to decouple growth from finite resource consumption in which the emission of waste is avoided, the materials are kept in a system and are efficiently used and where the regeneration of natural systems is taken into account (Ellen MacArthur Foundation). The cities of the future demand collaborative work, it is a pillar of the circular economy approach, the articulated work of actors linked to the growth of cities must be promoted, which should not be limited to its local scope, but at the global level.
How this panorama can affect the 2030 agenda and the Paris Agreement objectives?
The sustainable development goals (SDG) promoted by the United Nations in 2015 address under SDG 11 the creation and promotion of sustainable cities. Under the 17 SGDs, they hope that by 2030 it will be possible to have a global development that includes environmental, economic, and social aspects. Likewise, under the Paris Agreement, it is promoted that the nations of the world can promote an economy with low GHG emissions and climate-resilient communities, under which they maintain a global temperature rise this century well below 2 degrees Celsius above pre-industrial levels.
However, the current precedents in the world economy indicate a growth model based on the uncontrolled exploitation and acquisition of primary materials, the free use of sinks that have contained solid and gaseous wastes, as well as environmental and health impacts.
Generating sustainable cities
Under a circular economy scheme, new ways of approaching the production and consumption of resources are explored. Likewise, urban mining and metabolism of cities, regenerative cities, and material passports are approaches that go hand in hand with what is proposed by the circular economy in cities.
The approach of Regenerative Cities promoted by Herbert Girardet highlights the model of development and operation that cities have had, of unlimited consumerism and without a measure of consequences on the environment, health and other factors. Through this, cities and their inhabitants are urged to find ways to regenerate the ecosystems from which we have taken resources.
Likewise, the implementation of Material Passports is a very clever way to tackle the problem of waste generated in the construction sector. Only in Europe, the percentage of Construction and Demolition waste represents the 25-30% of the total waste generated, also, this is one of the sectors that consume the most resources at the regional level. Under material passport is possible to promote reversible building design in order to optimize the circular value chain of the construction sector.
This is the best time to promote change
Population growth and the climate change we are facing are the two main factors currently leading to the search for tangible actions so that cities migrate from a linear to a circular model.
The built environment in urban areas accounts for 39% of our total CO2 emissions. The UN-Habitat report estimates that 60% of the urban areas needed by 2030 still need to be built. It also indicates that 75% of the infrastructure necessary for 2050 is about to be built. The scenario is already set, the challenges that cities experience and will experience in the near future, at least until 2050, are known. Starting with this data, it is possible to start planning the cities of the future. In addition, it is necessary to get out of business as usual, and promote innovation on the way to a circular economy. Likewise, faced with the scenario of scarcity of raw materials, new alternatives for effective resource management are necessary, for which, technology plays an important role.
The World Economic Forum assumes that investment for infrastructure alone reaches USD 3.7 trillion per year until 2050. Such investment can generate great value, not yet estimated. In this sense, promoting sustainable growth against this level of investment is essential under parameters where further contamination is avoided, GHG emission, where the circularity of materials is ensured, and where the regeneration of systems that supply resources to cities is taken into account.
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Article written by Ing. Melissa Capcha (Master student at Kiel School of Sustainability)