Future carbon stock projections in Japan with increased residential and non-residential wooden construction

This study estimated the carbon stocks in Japan’s building stock till 2050, categorizing buildings according to use and number of stories and examining scenarios that promote wooden construction including non-residential and medium- to high-rise buildings. Previous projections have largely focused on residential buildings, and the influence of increased wooden construction in other building types has not been sufficiently evaluated. To address this, multiple future scenarios were developed based on projected floor area stock, including a conventional construction scenario and alternative scenarios that progressively expanded the range of buildings suitable for wooden construction. Carbon stocks were then estimated for each scenario. The results indicate that carbon stocks in 2050 declined compared to 2018 levels under conventional construction trends, whereas those increased under expanded wooden construction scenarios, reaching approximately 260 million t-C (about 1.3 times the 2018 level). This amount is equivalent to the carbon stock of approximately 2.17 million ha of Japan’s planted forests, or approximately 22% of the total planted forest area in Japan, highlighting the substantial carbon storage potential of urban buildings. Increased wooden construction also delays the stage at which building carbon stocks begin to decline and are counted as emissions. These findings suggest that maximizing carbon sequestration in the building sector requires expanded use of wood not only in residential buildings but also in non-residential and medium- to high-rise structures.