only the efficiencies but also resource cycles and carbon intensity of these urban systems and processes. Systemic transformation involves further innovation and integration of the above verticals and ultimately the establishment of new resourcing and servicing systems for urban regions that are optimized for decarbonization purposes. Transitions from legacy systems or sectors (i.e. the vertical columns) to integrated new systems (i.e. the horizontal columns) as part of an overall transformation of urban metabolism has been the central focus of the “urban nexus” agenda (Deutesche


Gsellschaft für Internationale Zusammenarbeit [GiZ] and ICLEI-Local Governments for Sustainability 2014), in which a city’s energy, water, food and waste systems are integrated for optimal efficiency and resilience.4


As cities push to further decarbonize systems and infrastructures, and to transform these into low-carbon and renewable energy sources, new and different types of urban systems are required in five areas, as shown in Figure 5.7.


Figure 5.7: Key elements of urban decarbonization pathways


Factor-four reduction in the embodied or upstream energy used to produce the goods, materials, and food to meet the human needs and wants of city dwellers. Reducing the embodied carbon footprint of urban-industrial society involves both cross- optimizing energy, materials, water, and nutrient cycles within cities and their related supply chains (i.e., a circular economy approach).


Innovations to reduce the contribution of energy services (heat, light, mobility, power, information processing) to the meeting of human needs and wants (e.g., access to comfort, health, security, education), giving particular attention to changing behaviors and social norms (i.e., broad based adoption of low-carbon vegetarian diets).


Urban planning and development regulations and models that establish energy efficient built forms, transit-oriented development patterns, and reduce goods and people mobility requirements.


Energy supply transition from carbon-based fuels to the establishment of de-carbonized electrical grid systems involving integrated micro-, mini- and macro-grids, including for electrified transportation systems.


Waste heat and bioenergy production from organic wastes and wastewater solids, including the gener- ation and use of biogas (which also addresses the challenge of urban methane emissions, as a carbon equivalent requiring priority management).


4 Examples of such nexus systems include: (1) Linköping (Sweden), which is harvesting biogas from multiple organic waste sources for transportation and other uses; (2) Växjö (Sweden), which has developed a regional forestry and biomass management system that supports the city’s 2020 target of 50 per cent of the city’s new buildings to be built from renewable wood resources, replacing carbon-intensive and non-renewable resources; (3) Toronto (Canada), where in 2014, the Toronto Regional Conservation Authority established a business partnership (which includes Canada’s largest international airport) to operate a regional materials exchange, which by 2019 had recycled 18,500 tons of waste materials among its members, thereby reducing further greenhouse gas emissions.


Achieving Urban Transformation: From Visions to Pathways


105


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