The first article in this short series based on a PhD thesis from Curtin University’s Dr Vanessa Rauland looks at the myriad opportunities available for decarbonising our cities, demonstrating the potential for urban development to dramatically assist in tackling climate change.
3 February 2014 — Scientists have called for a reduction of carbon in the global economy by 80 per cent by 2050 in order to keep global warming below two degrees of pre-industrial levels. Despite occupying only around 2.5 per cent per cent of the planet’s landmass, research suggests that cities are responsible for up to 80 per cent of global greenhouse gas emissions, though there is still debate on their exact contribution. Cities and urban areas consume extraordinary amounts of natural resources and discharge considerable volumes of waste into the atmosphere, waterways, oceans and soil. As a result, cities, through their built infrastructure, local activities and global consumption habits, are having an increasingly wider impact on the global environment, most notably in the form of human-induced climate change.
Nevertheless, cities are also extremely well placed to address many of the problems they face, through their ability to re-design themselves, their capacity to innovate and their unique decision making capabilities. These attributes can dramatically affect the amount of energy and resources consumed and emissions produced in cities and urban areas, making them a powerful force in global GHG mitigation.
Opportunities to decarbonise through urban development
Carbon has played an important role in the formation and reformation of cities for centuries. The availability of cheap fossil fuels has been a driving force in the rapid expansion of cities and has dramatically shaped our urban form. It has enabled and facilitated the development of car-dependent suburbs and allowed houses to continually increase in size. Over the last century in particular, this cheap fossil-based energy has meant little regard has been paid to things such as energy efficiency in buildings and other critical urban design features (such as walkability) that were fundamental elements of older cities.
As a result, abundant carbon abatement opportunities now exist within the built environment. While many are specifically related to energy efficiency (See McKinsey & Company’s greenhouse gas abatement cost curves), abundant decarbonising opportunities also exist around construction processes and building materials (low carbon alternatives), transportation and urban resource management (energy, water and waste production and management). The first article in this series highlights some of these opportunities, demonstrating the potential of urban development to dramatically assist in the decarbonising process.
Emissions are generated during the construction process of developments through onsite power and water use and the transport of materials to site, as well as from waste produced from unused materials (construction and demolition waste). Currently, around 42 per cent of waste generated in Australia comes from C&D and around 50 per cent of this ends up in landfill. There are also emissions associated with transporting waste to landfill or a recycling facility.
However, the GHG emissions associated with these processes can vary considerably depending on the construction approach and techniques used. The use of prefabricated materials, for example, has many environmental and GHG benefits, such as the reduction of waste produced onsite compared to traditional construction approaches and fewer embodied emissions in the materials due to greater potential for onsite re-use of materials during the manufacturing process. The time needed to construct a development is also reduced through this process, which in turn reduces the amount of onsite power (electricity) and transport fuel required. All this contributes to reducing not only onsite GHGs, but also costs, which can increase the affordability of buildings, and in particular of housing.
Embodied carbon in materials
Embodied energy or embodied carbon typically refers to the emissions associated with the production and transportation of materials used to construct buildings.
New research is showing that embodied carbon is responsible for a growing proportion of a building’s life cycle emissions, and can be as high as 62 per cent, largely because energy efficiency within buildings is increasing, thus reducing the operational emissions of buildings.
However, significant emissions reductions are possible if alternative materials are used. For example, choosing to re-use materials that are already onsite or purchasing recycled materials generally produces far fewer emissions than using new materials, depending on the type of material and its production process.
Many new low carbon materials are also being developed; materials that use either low carbon supplements such as fly ash, or cleaner production processes such as the use of renewable energy. Some studies have shown that the amount of embodied water in materials could be just as significant as the amount of energy, which can also have a significant impact on emissions, particularly if the water used is sourced from energy intensive processes such as desalination.
Finally, EC can also vary considerably depending on where materials are sourced – locally, regionally or internationally – and how they were transported to site.
Energy production and management
Energy is a particularly important component of any development, as the majority of life cycle emissions from the built environment generally come from energy related activities. However, the emissions associated with energy production and consumption within a development can vary considerably depending on a variety of factors such as the design and type of buildings, thermal efficiency, appliance efficiency, occupant behaviour and renewable energy generation.
Different building types have been examined in terms of their energy efficiency, with studies showing that denser urban form is generally more thermally efficient than single detached housing. The design of buildings can also dramatically affect the amount of energy required to run them. Well-known building techniques such as solar passive design have been extensively studied and are shown to significantly reduce the amount of artificial heating and cooling required in buildings. There are also a variety of energy efficiency measures such as improved insulation and alternative heating and cooling technologies that can significantly reduce energy requirements.
Significant variations in emissions can also occur depending on the source of the electricity supplied to buildings within a development. Conventional grid electricity sourced predominantly from coal is the most emission intensive form of electricity production and the primary cause of climate change. Electricity sourced from natural gas produces fewer emissions, and is particularly efficient when used in a way that supplies power and heating (co-generation) or power, heating and cooling (trigeneration). The notion of small-scale, decentralised energy production (both from fossil fuel and renewable sources) is becoming increasingly popular as a low carbon source of power and is well suited to the precinct scale. Other decentralised low carbon or carbon free sources of energy include photovoltaic panels, solar hot water heating, small-scale geothermal heat pumps and small-scale wind.
Purchasing “green power” is another option, which in this case eliminates the emissions associated with electricity consumption onsite.
The supply and treatment of water is another critical element to include in the GHG analysis of new developments. Water management is becoming increasingly connected to energy and carbon emissions as more cities, particularly in Australia, begin to rely on energy intensive forms of water supply and treatment such as desalination. The connection between energy and water, and thus emissions, has been extensively examined in the literature.
While GHG emissions can vary considerably depending on the technology used to produce water – for example, through desalination, treating recycled water or using dam water catchments or bore water – emissions in fact occur over the water entire cycle, including through the distribution of water, the consumption of water and the treatment of wastewater. While some studies have examined the environmental savings associated with decentralised water management and warn of the danger of locking into new energy intensive centralised systems such as desalination, opinions still vary as to which is the most efficient or emission intensive form: small scale or large scale.
Regardless of the scale debates, research is showing that water has become one of the biggest energy users in cities, and this is thus a critical area to tackle in urban development. Some question whether utilising renewable energy could be a way to offset the GHG impact of the rising energy use, though there are potential issues associated with making offset claims.
The amount of water needed within a development will also vary depending on the urban design, which includes how gardens and public landscaping are managed. Water efficiency measures in buildings will affect the amount of water required as well. Ensuring that water efficient appliances and grey water/third pipe systems are built into developments from the outset can optimise the water efficiency associated with the building infrastructure.
Development approaches that use water sensitive urban design require much less water for irrigation, and can provide opportunities for alternative storm water treatment, all of which can dramatically reduce GHG emissions. Optimising local water sources and recycling have many environmental benefits and can dramatically reduce emissions, though few precinct-scale initiatives have assessed this.
The waste sector in Australia produces around 11 megatonnes of GHG emissions annually. The GHG emissions associated with managing solid waste can vary considerably depending on the waste management technique adopted. Currently, around half of the waste produced in Australia ends up in landfill, which is a particularly inefficient and emission intensive form of waste management due to the production of methane emissions during the anaerobic digestion of organic materials.
The energy related GHG emissions associated with solid waste management and different treatment strategies have been reviewed in academic literature. Waste management options that produce fewer emissions include waste to energy technologies through incineration and various forms of gasification.
However, the concept of resource recovery (re-using waste) is the optimal way of dealing with waste, that is, viewing waste as a resource. This will no doubt play an essential role in decarbonising cities into the future. Resource recovery essentially involves re-using, recycling and composting as much of the waste as possible. This not only has the potential to significantly reduce emissions, but also helps to create a more circular metabolism within our cities.
The very first step in any waste management process, however, should be to minimise or avoid the amount of waste generated in the first instance. Encouraging society to minimise waste is likely to be challenging and will probably involve local behaviour change programs. Increasing knowledge around recycling, and improving the process, can also be facilitated by ensuring sufficient infrastructure is in place to enable good behaviour (for example, clearly marked recycling points). New waste collection techniques such as municipal vacuum waste, which sucks waste through an underground network of pipes to one or several collection points within a city, can also help to encourage better recycling. In addition, it can dramatically reduce the transport emissions associated with waste collection, improve the efficiency of recycling and add amenity by reducing the number of garbage trucks on the road and the number of collection days. This system can also allow for more compact urban form by eliminating the need for roads large enough for garbage trucks to manoeuvre through.
Transport fuels used by residents will impact the GHG emissions associated with an urban development. Different modes of transport (for example, trains, light rail, buses, traditional cars and electric vehicles) generate varying amounts of GHG emissions. Vast academic literature has analysed the differences in transport GHG emissions associated with different urban forms both internationally and in the Australian context, with a strong correlation being demonstrated between higher density and lower transport-related GHG emissions.
Moreover, even between cities with the same mode of transport, emissions can vary depending on the fuel source. For example, the emission intensity of an electricity grid will affect transport emissions associated with rail, if the rail network is drawing electricity from the grid. Electric-based transport systems (trains, light rail or electric vehicles) that recharge using renewable energy can significantly reduce transport-related emissions.
Urban development that encourages low carbon and carbon free transport modes, such as walking, cycling and access to efficient public transport options, can dramatically reduce the amount of GHG emissions associated with a development. Encouraging car share schemes to operate within urban areas can also help to reduce car ownership and subsequent vehicle kilometres travelled. It is therefore essential that these emissions be factored in when designing a development, and thereafter, regularly monitored.
Key areas for carbon reduction in urban development
The six broad areas of emissions outlined above are identified as key emission sources within precinct-scale urban development. New research proposes that these be considered as a broad framework to help guide any developer to calculate their developments ongoing carbon footprint.
Proximity and density
Proximity and density are critical factors in decarbonising cities. They are key to facilitating better public transport infrastructure and decentralised urban resource management options such as co- and trigeneration, as well as providing more efficient and compact housing options. These aspects of a city (for example, housing types, transport modes and energy, water and waste infrastructure) are all part of a city’s built environment and create its urban form, which ultimately determines its resource consumption patterns and the greenhouse gas emissions associated with it.
Today, cities and their built form are identified as being a vital part of the global response to climate change.
From “buildings” to the “communities” – why the precinct level is best for decarbonising
While efforts to reduce emissions from the built environment previously focused on individual buildings, as can be seen by the plethora of rating tools that exist to assess and encourage better building performance, a shift in focus has occurred in recent years to capture additional elements at the neighbourhood and precinct level. Such tools have demonstrated the greater emissions abatement potential when larger systems within the built environment, such as precinct-scale energy, water, waste systems and transport options, are included. Buildings are thus no longer being seen in isolation, but as a part of an integrated and dependent wider precinct system.
Although the neighbourhood “unit” or level has been identified and discussed in literature as a critical element for urban planning for over a century, it is only recently that this level has been associated with having abundant opportunities for sustainability and carbon reduction. These abatement opportunities, together with the effectiveness of implementation, have made the precinct level the optimum scale for addressing emissions within cities.
Defining the precinct
A precinct is loosely defined here as an area within a city made up of two or more buildings within a street, up to the size of a suburban development. Importantly, a precinct uses shared infrastructure, such as roads, energy, water and waste management systems. It can be a new development or a re-development and, while it can be purely residential or commercial, ideally it will incorporate mixed uses, thus providing a hub or agglomeration of activities and multiple participants.
There are many advantages of moving beyond the individual building scale to a precinct scale when attempting to decarbonise the built environment. For example, urban land development can take into account the urban and regional structure and form in terms of infrastructure provision, including both traditional centralised and distributed forms of resource management, as well as opportunities for greater public transport infrastructure.
Key reasons to target the precinct scale
This research identifies five key reasons for targeting the precinct level. First, by going beyond the building scale, additional elements that contribute to emissions can be factored into carbon-related decisions. Second, it is the scale at which communities function. Third, it is the scale at which developers work. Fourth, this level has greatest interaction with local government and, finally, it is the scale at which emerging technologies appear to perform best. These are discussed further below.
Allows additional urban factors to be considered
When discussing the built environment in terms of sustainability and its emissions contribution, the traditional focus has predominantly been on buildings. However, broadening the scope to the precinct scale allows a variety of additional factors to be taken into consideration, many of which contribute significantly to urban carbon emissions but are often seen as beyond a developer’s immediate control. By incorporating these additional factors, such as the transport options within a precinct and its management of resources, a deeper understanding can be gained of the total carbon implications associated with the built environment.
A framework that allows a developer to assess and compare various design approaches based on their costs and benefits can enable developers to make more informed decisions on important precinct infrastructure. This will help to lower the overall footprint of the development, and thus make the process of becoming carbon neutral significantly easier.
Scale of communities
The social and cultural dimensions of cities have been well recognised as a key factor in achieving sustainability outcomes. The social connections and interaction between people largely occur at the community scale. One paper notes that the “community” is increasingly identified as a space for realising pro-environmental change. As a result, it is receiving greater attention by policymakers and academics, evidenced by the increasing number of behaviour change initiatives targeting and engaging the community on climate change and sustainability issues.
Communities have also been identified as places where organic social change occurs in the form of grassroots initiatives – innovative niches with the potential for wider societal transformation largely due to the local networks, businesses and organisations that exist at the community level. The unique set of skills, experience and local knowledge that exists within local communities puts them in an ideal position to respond to local environmental challenges and issues more effectively.
Communities also play an important role in shaping social norms and practices. Normalised pro-environmental behaviour has been recognised as a key factor in transitioning to low carbon communities. While having the right technical and infrastructural solutions in place is important to provide opportunities for people to make the right choices, it has been identified that societal transformation has to include interactions between social and cultural life and physical and technical systems.
Scale of developers
Precincts and neighbourhoods are the scale at which development generally occurs, and therefore the scale at which developers are used to working. Developers are also accustomed to interacting with local governments on regulatory and planning issues, which can create opportunities for greater collaboration and working together to share both the costs and benefits associated with creating low carbon communities.
Local government has long been identified as an ideal scale for tackling climate change. The development of Local Agenda 21 and ICLEI – Local Governments for Sustainability, along with the introduction of various sustainability initiatives such as Cities for Climate Protection, are evidence of the willingness and effectiveness of local councils in addressing sustainability and climate change issues.
Since local governments have authority over many of the planning controls within their local government areas, such as land-use zoning, buildings, waste management and other common infrastructure, they are well positioned to create strategic policies for developers that ensure certain sustainability outcomes. Furthermore, as local governments already manage many of the systems and infrastructure and are increasingly being seen as early innovators and adopters of efficient technologies, this can provide an excellent basis for developers in creating low carbon developments.
Local government is not only the closest level of government to developers, but also to the community. They therefore have the greatest ability to influence individuals and affect change within the community, by enabling better dialogue between citizens, developers and local decision makers.
Scale of emerging low carbon technologies
Precincts provide an ideal platform to trial and deploy existing technologies and systems in an integrated manner to achieve the greatest environmental, economic and social outcomes. They provide the scale to test commercial viability and the ability to evaluate and replicate solutions. Working at the level of the precinct affords an opportunity to test the “systems thinking” needed to better understand the many and varied interactions between the infrastructure and systems that underpin urban life.
The precinct is increasingly being identified as an ideal scale for new and emerging low carbon technologies. Examples of the efficiency gains available through localised systems include the use of co- and trigeneration, renewables, localised water systems, solid waste recycling systems and many technologies associated with resource efficiencies. This scale provides great opportunities to test multiple technologies and systems in an integrated fashion at this smaller city level. Integrating technologies, systems and planning in a strategic way can provide numerous economic and environmental benefits and efficiencies that can be an order of magnitude greater than when they are pursued in isolation.
Low carbon case studies
Many well-known eco-cities, districts and low carbon communities around the world have demonstrated various elements of the precinct-scale carbon reduction opportunities mentioned above. Some of the most recognised and promoted developments include BedZED in the UK, Vauban in Germany, Hammerby Sjostad in Sweden, Western Harbour in Malmo, Sweden, and Masdar City, in the United Arab Emirates.
However, since there is currently no defined way of calculating the emissions associated with precinct-scale urban development, it is difficult to compare the developments as each has calculated various sources of emissions and asserted their achievements in diverse ways. This issue will be discussed in the next part of this series.
The current design of Australian cities based on large houses in low-density dispersed car dependent suburbs is extremely resource and emission intensive. The large scale centralised management of resources in cities, based on outdated technologies and compounded by ageing infrastructure, is further exacerbating the problem.
This low density, sprawled urban form built around centralised infrastructure, which has dominated western 20th century urban planning, remains the focus of countless cities around the world. Many global reports, highlighting the strong interconnection between climate change, urbanisation and infrastructure, have warned of the environmental consequences if new and expanding global cities, particularly in developing countries, adopt traditional 20th century low-density city design based around the car and centralised power, water and waste infrastructure.
If cities around the world continue along a “business as usual” pathway, and if new cities adopted similar patterns of design, then a significant increase in emissions, along with numerous resource concerns can be expected. However, it is argued here that many opportunities exist to transform cities, which will involve embracing new low carbon designs and more efficient and resilient urban systems and processes, all of which can be tacked at the urban development level.
Read part 2.
Dr Vanessa Rauland is a lecturer and project coordinator at Curtin University Sustainability Policy (CUSP) Institute. She recently completed her PhD on “decarbonising cities”. Dr Rauland is the co-founder of SimplyCarbon, which helps to reduce organisations’ carbon footprint and improve the efficiency of their operations.
A full list of references can be found in Dr Rauland’s PhD thesis, Decarbonising cities: certifying carbon reduction in urban development.