Road life-cycle carbon dioxide emissions and emission reduction technologies: A review

Carbon dioxide (CO₂) emissions from the road sector have attracted increasing attention in current years. This paper attempted to provide a systematic review of the existing research efforts on road life-cycle CO₂ emissions by analyzing the system's boundary division, identifying the CO₂ emission contributions of each life-cycle phase, listing major emission contributors, exploring related emission reduction technologies, and giving directions for future development. The research showed that the road life cycle is usually divided into five phases: material production, construction, use, maintenance and end-of-life (EOL) phases. The use phase and the initial construction stage (including material production and construction phases) contributed the most CO₂ emissions during the road life cycle. In detail, the production of cement, asphalt and steel were the three main emission contributors in the material production phase. The pavement roughness, albedo, and concrete carbonation were the main factors affecting emissions in the use phase. In addition, emission reduction technologies such as using recycled materials and recycling techniques, lowering mixing temperature, and equipment energy substitution were commonly used to reduce emissions from material production and construction phases. The application of emerging technologies such as carbon capture and storage, carbon sink, and the use of hydrogen, solar and photovoltaic in the road sector may have emission reduction potentials and should be highlighted more in future studies.