Contrastación de hipotesis

The overarching aim of the research presented in this thesis is to understand what role embodied carbon abatement could have in meeting the UK’s medium term sectoral and long term national carbon reduction targets. Within this broad aim there are a number of more specific aims and objectives set out in the following pages. Table 2 on page 26 summarises these aims and indicates by what means and where in the document they are addressed.

The construction sector undertakes a broad range of activities to produce a highly diverse output and depends upon a complex supply chain that spans international borders. Any analysis of embodied carbon in construction must therefore begin with an investigation of the origin, magnitude and distribution of emissions across these activities and supply chains. Such an analysis can be adopted from a number of perspectives, whereby emissions are attributed to a final product, e.g. houses, offices, factories etc., an intermediate activity, e.g. raw material extraction, material manufacture, transport to site etc., or by spatial origin e.g. emissions arising in the UK, EU, China etc. All of these perspectives are pertinent in understanding the mitigation potential. Understanding the impact of final products reveals the potential for mitigation through changing demand patterns, e.g. reducing the number of new offices constructed. Understanding the relative impacts of intermediate actions can highlight carbon hot-spots or intervention points with the greatest reduction opportunities, e.g. key materials or processes where one change could yield substantial reductions. Finally, with climate policy determined independently at company, sectoral, national, and international levels, an understanding of the spatial origins of emissions is critical in formulating an appropriate policy response. Only two prior attempts have been made to estimate

the embodied emissions attributable to UK construction (BIS, 2010; GCB, 2013b), both of which considered only the intermediate activity perspective and suffered from limitations described in the following chapter. Therefore the first research aim is to:

Conduct a robust evaluation of the embodied carbon emissions associated with the UK construction sector supply chain

Within this aim the objectives are to:

» Develop a time series of annual embodied emissions of the construction sector.

» Evaluate the embodied emissions from multiple perspectives; namely: by final product, intermediate activity and spatial origin.

From this evaluation, a number of priority sources of embodied emissions are revealed; the largest of which are emissions from materials extraction, manufacture and production. Emissions from transport and construction activities are also notable and can be reduced through measures such as using low emission vehicles to transport materials and the efficient use of construction plant (Ko, 2010). However, as the majority of embodied emissions are associated with the production of core building materials, substantial embodied carbon reduction will only be achieved through improvements in material manufacture or a reduction in the use of those materials with the most carbon-intensive supply chains. The construction sector has limited influence on the manufacturing processes of key materials such as steel and cement. Both academic authors and industrial roadmaps have suggested that there is minimal scope for significant emissions reduction in the manufacture of these materials in the short-medium term as production processes are already highly efficient and, in some cases, are approaching practical and thermodynamic limits (Allwood & Cullen, 2012; WSP et al., 2015b; WSP et al., 2015a). Consequently, opportunities to minimise emissions primarily involve reducing the use of these materials. The construction sector can achieve this through the adoption of a variety of alternative materials, technologies and practices (Cabeza et al., 2013). The numerous options include: substituting materials derived from naturally occurring renewable substances; materials that incorporate wastes or recycled content;

materials that have been repurposed or sourced for re-use from other sites; and construction products that have been optimised through novel production techniques. Some of these options are doubtless more practicable than others.

Consequently, the second research aim is to:

Use the literature to appraise options that could deliver substantial reductions in the use of construction materials with carbon-intensive supply chains

Within this aim the objectives are to:

» Identify the alternative materials, technologies or practices which could substantially reduce the demand for carbon-intensive materials in the construction sector.

» Assess the suitability of such alternatives in a UK context. i.e. could they be adopted in a timescale that is compatible with UK climate targets and subject to acceptable social, economic and environmental trade-offs?

The appraisal of options reveals a wide variety of alternative materials are available.

However, whilst there are many examples of their successful use, there remain a multitude of barriers to widespread adoption of alternative materials amongst practitioners involved in the design and construction process. Many of these barriers are not associated with technical performance but with perceptions or cultural norms within the industry. However, as highlighted by Watson. et al (2012), minimal qualitative work assessing these barriers has been completed. Understanding the barriers to adoption of alternative materials requires not only determining what must be done to demonstrate performance and gain acceptance but also an understanding of the root causes of the resisting behaviour and conservatism of industry practitioners (Jones et al., 2015). Therefore the third research aim is to:

Conduct new research to understand the cultural, behavioural, and perceptual barriers to adoption of alternative low carbon building materials amongst industry practitioners involved in design, specification and construction

Within this aim the objectives are to:

» Identify the barriers to initial adoption and widespread uptake of a selection of example low carbon building materials.

» Explore the underlying industry structures and practices that support these barriers.

» Identify measures which could accelerate the adoption of low carbon building materials.

In response to a growing interest in embodied carbon, the industry has recently engaged in a variety of data gathering efforts, such as the public WRAP Embodied Carbon Database (WRAP & UKGBC, 2014), which allows users to share building level life cycle assessments (LCAs). Schemes such as this and published benchmarks from groups such as the RICS (2012), are facilitating relative performance assessment between designs. However, this bottom up data has yet to be integrated with top down data representing overall sector output. This integration is crucial for design teams and policy makers to assess not only performance relative to their

contemporaries, but absolute performance in the context of UK climate mitigation strategies. In the long term it is essential that a link is formed between sector level reduction targets and the tangible project level benchmarks utilised by design teams. This is the only way in which current performance can be assessed and the scale of future requirements determined. Without this link it is impossible for policy makers to determine the adequacy of any proposed policy intervention, such as extending regulation restricting operational carbon to include embodied carbon.

Therefore the fourth research aim is to:

Create an analytical framework for translating sector emission reduction targets into project level targets, suitable for use by design teams

Within this aim the objectives are to:

» Develop a UK Buildings and Infrastructure Embodied Carbon Model (UK BIEC) that integrates emissions outputs from a top down sector level model with a database of bottom up building level LCAs.

» Explore the means by which such a model could facilitate future assessment of progress towards sector reduction targets and the setting of project targets.

The creation of such a model also facilitates scenario analysis, a means commonly used to appraise possible futures and responses. In addition to changing patterns in material demand, a key strategy in reducing embodied carbon could be minimising aggregate demand for new buildings and infrastructure. By contrast, current Government strategies and industry projections assume significant growth in industry output over the coming decades in key areas such as housing and infrastructure. This additional output has the potential to drive growth in embodied carbon and restrict the ability of the industry to achieve sector carbon reduction targets in absolute terms. In essence: the greater the growth in construction activity, the less carbon-intensive that activity must be. Thus, significant growth in overall activity implicitly imposes more severe carbon reduction targets at a project level, necessitating the adoption of a different range of reduction strategies. In an attempt to shed light on the impacts of this projected growth in demand, the fifth research aim is to:

Use the new framework to explore the role for demand reduction in meeting embodied carbon reduction targets

Within this aim the objectives are to:

» Formulate a series of scenarios that reflect plausible future levels of demand for new building and infrastructure stock.

» Evaluate the embodied emissions implications of these scenarios in relation to sector and national carbon reduction targets.

In addition to demand side responses, there is space for additional drivers of supply side responses, be they industry-led agreements or regulatory requirements and incentives. Industry practitioners have already begun to discuss potential avenues for regulation of embodied carbon through events such as the Alliance for Sustainable Building Products (ASBP) ‘Embodied Carbon: Why, how and when? Debate’, hosted in April 2014. A group of practitioners also formed a self-titled Embodied Carbon Task Force in 2014, which lobbied for inclusion of embodied carbon as an Allowable Solution under the proposed Zero Carbon building regulations (Battle, 2014).

As local authority requirements and international precedents for regulation of embodied carbon emerge, there is a clear need for an appraisal of potential policy responses. These responses must also be situated within a longer pathway towards a low carbon construction industry. The policy response to operational emissions has been introduced gradually through the introduction of new regulation and a ratcheting up of existing policies. It is likely that embodied carbon will require a similar measured and progressive response. This response must also be responsive to changing targets for carbon mitigation and resilient to the shifting political landscape responsible for a turbulent regulatory environment. Consequently, it may be of benefit to position potential policy options within a range of dynamic adaptive policy pathways (Haasnoot et al., 2013). Such pathways would retain the flexibility to respond to changing circumstances, technologies and ambitions whilst highlighting critical short term actions and key decision making points. To this end the final research aim is to:

Identify possible policy responses and industry-led actions that could motivate substantial embodied carbon reduction

Within this aim the objectives are to:

» Assemble a list of possible policy responses and industry actions to reduce embodied carbon.

» Develop an initial set of dynamic adaptive policy pathways through a participatory approach with key stakeholders.

» Highlight critical short term actions and key decision making points for policy makers.

Recent high profile reports and initiatives, such as the introduction of the RICS methodology for calculation (RICS, 2012), the ICR (HM Treasury, 2013) and the UKGBC’s inaugural Embodied Carbon Week (UKGBC, 2014a) reflect the construction industry’s growing ambitions to reduce both operational and embodied carbon. The GCB Low Carbon Routemap for the Built Environment constituted a first attempt to translate these ambitions into tangible sector goals that are compatible with

national emission reduction targets (GCB, 2013b). However, as a result of focussing the bulk of project resources on operational emissions, the final recommendations only amounted to a first step towards determining a viable sector plan for embodied carbon. Furthermore, whilst the Routemap listed some potential solutions it did not address the barriers to adoption of low embodied carbon alternatives or propose a meaningful policy response. In aggregate, the research objectives presented here, represent a further step towards forming a credible, coherent and resilient plan for reducing embodied carbon. The following section elaborates on the methodologies used in meeting these objectives.