It is very important for waste to be controlled and appropriately treated in a waste treatment system because of its impact on the environment. This study quantitatively evaluates the current waste treatment system and suggests countermeasures based on their impact on reducing the environmental and treatment costs in order to solve waste treatment problems in Bangkok, Thailand. Evaluation models are applied to estimate the treatment and environmental costs in the current waste treatment system. This study shows that the contribution of carbon dioxide and methane gases from the current waste treatment system in Bangkok, Thailand to the greenhouse effect is large. Using the baseline scenario as a standard, the study provides a quantitative measure of the reduction in environmental costs that can be achieved by applying the countermeasure scenarios.