Abstract
In this paper, a life cycle CO2 assessment considering the CO2 absorption of trees in leaning type retaining wall works accompanying road construction on the slope of a mountain was performed. Two cases of the leaning type retaining wall works were studied. In Case 1, the retaining wall is constructed by piling hollow blocks which were filled with surplus soil generated in the site, while ready-mixed concrete is placed in situ in Case 2. The hollow blocks used in Case 1 were precast concrete products with a revegetation function. Three trees were planted in each hollow block. The CO2 absorption of trees was calculated by using the result of research at a retaining wall 13 years after construction. As a result, the CO2 emission in Case 1 can be reduced by approximately 33 percents comparing with that in Case 2. The use of hollow blocks in leaning type retaining wall works could greatly contribute to the reduction of CO2 emission. The CO2 absorption of revegetation trees in Case 1 is 2.3％ of the totally CO2 emission. Therefore, the growth of revegetation trees would be expected to lead a large amount of the CO2 absorption in the future.
