Environmental aspect is often neglected in traditional distribution planning process of a product. Especially in small-medium enterprises (SME) of developing countries where cost efficiency is the predominant factor. Bearing in mind that there is a large number of SME's performing logistics activities, the consideration of environmental aspect in their distribution planning process would be beneficial to climate change mitigation efforts. The purpose of this paper is to show the impact of environmental aspect should it be considered as a contributing factor in distribution planning. In this research, an adoption of CO-emission factor in an SME's distribution planning in Indonesia was simulated. The outputs of distribution planning with and without the factor consideration are then compared. The result shows that adoption of CO-emission factor would change the priority of delivery route.