Optimization of Construction Supply Chains for Greenhouse Gas Reduction

Introduction

There are regulatory, environmental, social and increasingly financial reasons for businesses to reduce the greenhouse gas (GHG) emissions associated with their operations (Blengini & Garbarino, 2010). This focus is of particular interest for the construction industry, as the built environment is seen as the domain with the largest potential for reducing GHG emissions (European Commission, 2011), because its energy consumption and the associated GHG emissions are so significant, accounting for ca. 40% of EU energy demand (Cheng, Pouffary, Svenningsen, & Callaway, 2008).

The built environment is therefore seen as a critical arena to achieve lower energy related emissions, through the construction of energy efficient new buildings and the energy retrofit of existing building. As a consequence, there are a large number of regulatory and public policy initiatives internationally, aimed at increasing building energy efficiency and reducing associated emissions, for example the Energy Performance of Buildings (Directive 2010/31/EU); increasingly more stringent national building codes; moves to implement green public procurement in respect of buildings (European Commission, 2014); innovative financial products such as: preferential green loans (Geller, Harrington, Rosenfeld, Tanishima, & Unander, 2006; Sweatman & Managan, 2010), the UK Green Deal (DECC, 2010), and the Property Assessed Clean Energy (PACE) initiatives in the USA (Ya He, 2012).

While these measures represent important innovations of policy, they are generally focused at the immediate building scale, and on the use of energy during the operational phase – the so-called operational energy. However, buildings are responsible for GHG emissions not just during their operation but throughout their lifecycle, arising from energy consumption and process emissions, during the extraction of raw materials; processing and manufacture; transportation; construction; renovation; and end-of-life activities in additional to the operational phase (Ayaz & Yang, 2009).

Historically, reducing GHG emissions in the built environment has been focused on minimizing operational energy, which typically accounted for 80% of life cycle energy of a building (Wallhagen, Glaumann, & Malmqvist, 2011) and the vast majority of a building’s life cycle GHG emissions. However the historic relationship between operational and non-operational GHG emissions and their relative significance is changing. As the building stock becomes less energy intensive in the operational stage, through more efficient designs of new builds and upgrading of existing buildings, the relative importance of GHG emissions associated with non-operational phases of a building’s lifecycle is increasing (Ayaz & Yang, 2009; Sturgis & Roberts, 2010). Additionally, the envisaged so-called ‘decarbonization’ of centralized energy grids (European Commission, 2011) will mean that energy used will be less ‘carbon intensive’, with less GHG emissions per kilowatt-hour (Jones, 2011), further increasing the relative significance of non-operational GHG emissions. A comprehensive reduction of GHG emissions in the construction sector needs to focus not only on the building itself and its operating energy performance, but also on the lifecycle of constituent materials and on the supply chains providing these materials. In this context, there is a pressing need to provide robust analysis of the GHG implications of construction supply chain configurations and to optimize supply chains in such a manner so as to minimize GHG emissions across the entirety of the supply chain.