Transportation has become one of the most significant contributors to CO2 in the world because of its fuel usage. Trees are planted on the roadside to reduce levels of CO2 in the air because trees have the ability to absorb CO2 to be used in the photosynthesis process. This ability will be maximized if the dispersion of CO2 is concentrated around the tree. However, there are some differing results from previous studies regarding this. Some research results have found trees can increase CO2 concentration and vice versa. Accordingly, this study aims to evaluate the effect of tree planting on the roadside in dispersing CO2 using a real 3D environment. The methods used in this research are CO2 emission analysis to obtain the amount of CO2. Then, Computational Fluid Dynamics (CFD) analysis is used to simulate the dispersion of CO2 in the study area both without trees and with trees. However, due to the mixing of air and CO2, this simulation uses a scalar mixing analysis. Some conditions are considered, such as the characteristics of buildings, the characteristics of trees, and environmental conditions. The result indicates that trees can decrease the velocity and increase the concentration of CO2 on the roadside but decrease CO2 concentration on the road. Tree planting can decrease the velocity by 4.3% in the value range 0.9-1 m/s. This condition increases CO2 concentration on the roadside. Trees can increase CO2 by 25% on the right of a roadside and increase CO2 concentration by 10% on the left side.
Aini et al. (Tue,) studied this question.