As the world moves toward carbon neutrality, efforts are underway to achieve Carbon Neutral Port (CNP) in the Japanese port sector. The importance of decarbonization or low-carbonization in terms of the construction of port structures is significantly increasing. In order to effectively promote low-carbonization, it is necessary to estimate the amount of CO2 emissions from the construction of port structures in advance of executing construction and to implement effective low-carbon measures based on the estimation. It is pointed out, however, that the estimation of the amount of CO2 emissions in advance of executing construction has uncertainties since the details of the construction work have not yet been determined. Therefore, it is important to clarify the boundary of the possible estimation and to sort the uncertainties.
Firstly, in this paper, for each situation in which CO2 emissions are estimated in advance of executing construction the main entity estimating the amount of CO2 emissions was organized. Next, the boundary of the possible estimation was clarified by organizing the CO2 emission sources related to the construction of port structures regarding the concepts, standards, and criteria for the existing environmental management. Then the calculation methods, which are “input-output analysis” and “process analysis” were organized. Finally, the amount of CO2 emissions from the construction of the port structure was estimated based on the CO2 emission factors calculated by the two methods, leading to a comparison of the estimated results. Based on the results of the estimations, the trend of CO2 emissions from each construction process, or the items such as material productions, machinery operations, and transportation, was discussed.

Key Words: port structure, construction, CO2 emissions, low-carbonization, input-output analysis,
process analysis, Carbon Neutral Port