CALCULATION METHOD OF CO₂ ABSORPTION AMOUNT OF SEAWEED BED ON CONCRETE BLOCK INSTALLED AS STRUCTURE

Abstract

 The promotion of the blue carbon increase can be considered as an effective measure to achieve the government’s target of carbon neutrality by 2050 which is absorbed by marine organisms such as marine plants. Generally, seaweed grows on the surface of concrete blocks installed in the coastal area depending on the nature of the block installation location. The installation state of blocks and the seaweed attachment state on blocks are different depending on concrete block types. In this study, an estimation method for CO₂ absorption of blocks as well as marine structures such as breakwaters was investigated based on the concrete block shape characteristics, and their installation states. For the flat-type armor blocks (type A), it was proposed to use the total upward-facing surface area of the block for the calculation. However, regarding the wave dissipating blocks (type B), the actual seaweed attachment surface area due to the unevenness of the random piling installation of blocks is larger than the predetermined surface area calculated from the crest width, slope length, and length of the breakwater. Therefore, a calculation method for the seaweed attachment surface area that applies the "ratio of random piling installation" was examined and a range of values between 2.0 and 2.5 was proposed as appropriate values. The amount of CO₂ absorbed by seaweed was calculated following the previous studies. The result obtained for the armor block type A was similar to the results achieved in the previous studies. Although the results of block type B and the whole body of the breakwater were smaller than the results obtained in previous studies, the calculation results were almost the same and larger when the "ratio of random piling installation" was applied.