Abstract
Buildings use a wide range of construction materials, and the manufacturing of each material consumes energy and emits CO2. Several studies have already been conducted to evaluate the embodied energy and the related CO2 emissions of building materials, which are mainly based on case studies from developed countries. There is a considerable gap in cases of developing countries regarding assessment of embodied energy and CO2 emissions of these building materials. This study identified the top five most used construction materials (cement, sand, coarse aggregates, hollow concrete blocks, and reinforcement bars), which are also prime sources of waste generation during construction in the Ethiopian building construction sector. Then, what followed was the evaluation of the embodied energies and CO2 emissions of these materials by examining five commercial and public buildings within the cradle-to-site lifecycle boundary. The evaluation results demonstrated that cement, hollow concrete blocks (HCB), and reinforcement bars (rebars) are the major consumers of energy and major CO2 emitters. Cumulatively, they were responsible for 94% of the embodied energy and 98% of the CO2 emissions. The waste part of the construction materials has inflated the embodied energy and the subsequent CO2 emissions considerably. The study also recommended several strategies for the reduction of embodied energy and the related CO2 emissions. The research delivers critical insights into embodied energy and CO2 emissions of the five most used building materials in the Ethiopian construction industry, as there are no prior studies on this theme. This might be a cause to arouse awareness and interest among the policy makers and the wider public to clearly understand the importance of research on this crucial issue to develop national energy and CO2 descriptors for construction materials, in order to take care of our naturally endowed, but yet fragile, human habitat.
Highlights
IntroductionAbout 50% of all materials extracted from the Earth’s crust are processed into construction materials [1]
The construction industry uses more raw materials by weight than any other industrial sector.About 50% of all materials extracted from the Earth’s crust are processed into construction materials [1].In building construction, a wide range of materials are used, and the production of each material consumes energy and emits CO2
Quantities of the building materials were evaluated from plans, quantity survey data, and data obtained from material suppliers
Summary
About 50% of all materials extracted from the Earth’s crust are processed into construction materials [1]. A wide range of materials are used, and the production of each material consumes energy and emits CO2. The United Nations Environment Programme (UNEP) reported that buildings and construction are responsible for more than 36% of the global energy consumed, and as much as 40% of energy-related CO2 emissions [2]. According to the UNEP, the amount of total buildings-related CO2 emissions (including energy-related emissions from buildings construction) in 2017 alone was more than 11 GtCO2 [2]. Buildings and the construction sector have the largest shares of global energy and emissions compared to other sectors, such as industry and transport
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