A Model for Assessing Embodied Energy and GHG Emissions in Infrastructure Projects

Construction and operation of buildings and infrastructure is a main contributor to emissions of greenhouse gases (GHG) in Sweden. The embodied energy of construction, meaning all the energy that is used until the completion of the construction project (see Figure 1), cause roughly 10 million tones of CO₂ equivalent emissions each year which equals to the emissions from all cars in Sweden (IVA 2014). About 6 million tones of CO₂ equivalent emissions are attributed to the embodied energy of roads, railroads and other civil works while the remaining 4 million tones are attributed to the embodied energy of buildings (IVA 2014). Although reducing energy use and associated GHG-emissions in road and railroad construction is prioritized by the Swedish Transport Administration (Trafikverket 2012), the GHG-emissions from such construction projects have increased in recent years (Boverket 2014). Many of the existing efforts to reduce energy use and associated GHG-emissions focus on individual phases of the life cycle and don’t take into consideration the effects at other stages during the whole life cycle of a project (Boverket 2011). A crucial step in the assessment of energy use and associated GHG-emissions is to clarify and categorize the different phases of a life cycle. Figure 1 shows a proposed categorization of life cycles phases and use of energy based on previous research (Davies et al. 2014). Buildings’ main use of energy happens during its operational phase from e.g. heating, lighting and use of electrical appliances (Sartori and Hestnes 2007). In infrastructure projects such as road construction the embodied energy is roughly equal to the operational energy for roads with lighting, or in fact considerably higher if the road lacks lighting (Stripple 2001).