Carbon footprint and embodied energy assessment of a civil works program in a residential estate of Western Australia

Abstract

Purpose: With building construction and demolition waste accounting for 50 % of land fill space, the diversion of reusable materials is essential for Perth’s environment. The reuse and recovery of embodied energy-intensive construction materials during civil engineering works programs can offer significant energy savings and assist in the mitigation of the carbon footprint. Methods: A streamlined life cycle assessment, with limited focus, was carried out to determine the carbon footprint and embodied energy associated with a 100-m section of road base. A life cycle inventory of inputs (energy and materials) for all processes that occurred during the development of a 100-mroad section was developed. Information regarding the energy and materials used for road construction work was obtained from the Perth-based firm, Cossill and Webley, Consulting Engineers. These inputs were inserted into Simapro LCA software to calculate the associated greenhouse gas emissions and embodied energy required for the construction and maintenance of a 100-m road section using. Two approaches were employed; a traditional approach that predominantly employed virgin materials, and a recycling approach.Results and discussion: The GHG emissions and embodied energy associated with the construction of a 100-m road section using virgin materials are 180 tonnes of CO2-e and10.7 terajoules (TJ), respectively. The substitution of crushed rock with recycled brick road base does not appear to reduce the carbon footprint in the pre-construction stage (i.e. from mining to material construction, plus transportation of materials to the construction site). However, this replacement could potentially offer environmental benefits by reducing quarrying activities, which would not only conserve native bushland but also reduce the loss of biodiversity along with reducing the space and cost requirements associated with landfill. In terms of carbon footprint, it appears that GHG emissions are reduced significantly when using recycled asphalt, as opposed to other materials. About 22 to 30 % of greenhouse gas (GHG) emissions can be avoided by replacing 50 to 100%of virgin asphalt with Reclaimed Asphalt Pavement (RAP) during the maintenance period. Conclusions: The use of recycled building and road construction materials such as asphalt, concrete, and limestone can potentially reduce the embodied energy and greenhouse gas emissions associated with road construction. The recycling approach that uses 100 % reused crushed rock base and recycled concrete rubble, and 15 % RAP during the maintenance period could reduce the total carbon footprint by approximately 6 %. This large carbon saving in pavement construction is made possible by increasing the percentage of RAP in the wearing course.