Net Zero: can cities deliver?
Many countries are outlining plans to achieve net-zero at various points this century. But, what does that mean and how can it be done? The International Panel on Climate Change (IPCC) just released their latest report which focuses on the review of mitigation efforts, and the impact of national climate pledges. There are a lot of changes that need to be implemented in order to achieve aggressive climate action goals.
Based on figures from BP, approximately 70% of emissions generated within cities are based on consumption. In a typical household, there could be hydro-generated electricity, natural gas for heat, and gasoline for the average vehicle. Future cities will need to develop integrated energy systems in order to reduce emissions. This approach will be much easier for bigger cities due to the amount of both new and retrofitted infrastructure.
Photo by: Nathan Cohen. The Hasegawa Green Building is located in Shibakoen, Tokyo, Japan across the street from Tokyo Tower. This living wall decorates the side of an otherwise ordinary low-rise building. Green walls have many benefits in busy cities ranging from helping control building temperature, to improving the state of mind of people walking by. It is important to consider that green walls cost more to maintain than regular building facades. For more stories follow @theengineeringnomad
The chicken-and-egg problem with electrification of cities continues for now, but it is only a matter of time before mass cooperation is necessary for reaching net-zero targets. Small scale projects are already underway that showcase the benefits of a centralized approach like the central heat distribution system and fuel cell buses in the city of Aberdeen, Scotland.
While direct energy consumption is a major focus for reducing emissions, decarbonizing our building materials is just as important when retrofitting existing buildings and constructing new ones. Concrete and steel production is an energy intensive and emissions heavy process. While these materials are common in construction now, there are lots of new building projects which are favouring wood for the main structural members.
Cross-laminated timber (CLT) is a common term in the field of wood construction. Simply put, CLT is a large prefabricated panel comprised of wood stacked in alternating directions and secured with structural adhesives. A recent project at the University of British Columbia showcases an 18-storey student residence with 17 storeys of CLT floors, and wood columns.
The added bennefit of using forestry-products as building materials is they can be grown and harvested locally, reducing the volume of emissions normally associated with shipping building materials around the world. We need cropping timber to absorb carbon in the air and then be turned into high quality timber and building materials. At the Future of Cities Summit, hosted by Tortoise Media in 2021, Tilly Collins of Imperial College London spoke about how locally resilient tree species would be best for ease of cultivation. When we are able to grow trees locally, and manufacture timber locally, we reduce the volume of carbon emissions emitted as part of the construction process.
We sometimes lose the architectural vernacular of an area when we begin to overdevelop areas trying to take advantage of all usable space. Many European cities can teach us a lot about design of communities; narrow streets provide for shade during warm weather, and roofs sloping towards gardens to reduce water consumption, and reduce water runoff on hardscaped surfaces. Some cities in the world have also begun to incorporate porous landscaping materials to reduce run-off. Referred to as “sponge cities in parts of Asia, they improve water management and reduce localized flooding in typically hard-landscaped areas.
Photo by: Nathan Cohen. Narrow streets and pathways tucked between old buildings in a bustling city makes Grenada a travellers paradise. The city is very European with flavours of Moorish architecture. The bright colours and overhanging plants from apartments above give life to the city. For more stories like this, follow @theengineeringnomad.
Simon Birkett is the founder of Clean Air in London, and participated in the Future of Cities Summit in 2021. According to Birkett, combustion is associated with 80% of air quality problems. Reducing emissions also improves air quality in cities. Per capita emissions are far greater in developed countries, so a combination of political leadership, and policy change are needed.
There are two broad categories of approaches that can be taken to reduce emissions: technological and lifestyle changes. A mix of the two will be required in order to achieve cleaner air and a net-zero target. Lifestyle change is a category of measures typically left out of cost-bennefit studies. And lifestyle changes can have “political costs” as well.
Photo by: Nathan Cohen. The caixaforum in Madrid has a verticalgarden on one of its exterior walls. Vertical gardens help increase greenspace while reducing the heat island effect in cities. In order to save on weight on the wall assemblies, some vertical gardens reduce the amount of soil for the plants by using nutrient and mineral rich water to hydrate the plants. For more stories like this, follow @theengineeringnomad
Current building codes and energy efficiency standards can be fairly prescriptive and point-systems can sometimes determine design decisions. For example: the LEED building system which categorizes buildings based on a rubric specifies a point system for the awards. Green Power and Carbon Offsets account for two points, and bicycle facilities count for one point. While both aspects are important, it is far more expensive to put in place a green power plan, than bicycle facilities.
There is still lots of work to be done in the development of net-zero cities. Existing frameworks are helpful, but there is still room for improvement in our net-zero ambitions. When we look around at cities around the world, there are lots of helpful design examples that we draw from in our combined efforts to reduce emissions and build healthy cities.
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This article was first inspired by the Future of Cities Summit, hosted by Tortoise Media in 2021.
Net Zero: can cities deliver us from the climate crisis host: Giles Whittel, Sensemaker Editor. Speakers: Tilly Collins, Senior Fellow & Deputy Director, Centre for Environmental Policy, Imperial College London, Simon Birkett, Founder and Director of Clean Air in London, Andres Guevara, Vice president region & city Decarbonisation, BP