Estimation of life cycle CO2 emission and energy cost of different building materials

Abstract

The construction sector of Bangladesh has seen massive boom in last few decades and is responsible for greenhouse gases contribution. In this research, an investigation has been made to develop empirical equations of life cycle CO2 emission and energy cost for seven most widely used construction materials of Bangladesh namely brick, cement, sand, steel; both from billet and scrap, stone chips, timber and concrete. Based on overall study, an attempt has been made to present a guideline to estimate life cycle energy cost and CO2 emission of different structural systems. To carry out the investigation, this research modeled two similar medium sized buildings each designed by finite element analysis using primarily Concrete and Steel. The models were based on a 914 m2 (9833 sq feet) floor area six-storey building. Both the superstructure of buildings has been analyzed individually using the empirical equations developed in this study. The major phases have been cradle to gate, transportation of component raw materials to site, construction of the building and finally demolition. Operational CO2 emission of the building has not been taken into consideration. Analysis result of the said six storey mid rise building showed that steel produced from ship breaking scrap consumes maximum energy in its entire life cycle and concrete emits maximum CO2 in transportation phase among all the materials considered in this study. This may be due to the fact that all the component materials are obtained from different source locations. Although in cradle to gate phase, concrete building emits 73% of the total life cycle CO2 and steel building emits 53.7% CO2, in construction phase emission of CO2 of concrete building is less than one ton whereas that of steel building is 26.9% of total emission. Considering total life cycle CO2 emission Steel building emits 1.7 times CO2 per square feet as compared to concrete building. Considering total energy cost, Steel building has 3.7 times energy cost per square feet than that of Concrete building. Based on the results it can be concluded that concrete building is more sustainable than steel building in perspective of Bangladesh.