台灣排放權交易制度之儲存機制設計之探討──以硫氧化物管制為例

An Economic Analysis of the Banking Design for the Permit Trading System in Taiwan: An Example of Sulfur Oxide Control

為賦予廠商在污染減量策略上有更大的彈性，許多排放權交易制度皆設有儲存機制，但儲存機制卻可能使環境品質產生較大的波動，此也隱含該機制所提供的減量彈性與環境品質穩定性間存有某種程度的抵換關係，故某些交易制度會透過儲存係數的設定，僅允許部分儲存的排放權移至未來，用以在兩者間取得適度的平衡，因此如何在推行排放權交易制度之初，設計出一個適切的儲存規則，乃是管制者需積極面對的課題。本研究建立一個排放權交易模型，並在允許儲存係數間可以不存在任何系統性關係的情況下，以台灣高屏空品區的硫氧化物管制為例，模擬政府若採用目前規劃的儲存機制或是直接沿用其他各國正在運行的機制，對於減量成本與環境品質可能產生的影響，進而協助管制者規劃適合台灣的儲存制度。本研究模擬發現，在一個假設為期五年且減量標準較為寬鬆的交易市場中，台灣若採用目前規劃的儲存機制或是其他正在運行的儲存機制，都不會對於空氣品質變異造成明顯的影響，故政府此時應以追求最大的減量彈性為目標，仿效美國的酸雨交易制度讓未用完的排放權全數無限期的儲存至未來，但當管制標準趨於嚴格時，不同儲存機制的影響變得顯著，此時政府應採芝加哥的Emission Reduction Market System，僅讓未用完的排放權全數儲存一年，但無論管制標準為何，現行台灣環保署規劃的儲存機制在減量彈性與維持環境品質穩定兩方面的表現都不是最佳的。

In order to provide more flexibility of pollution control for firms under tradable permit systems, many trading programs have the banking design. However, the design would cause higher environment quality variations. It means that a tradeoff exists between the flexibility of emission control and the environmental quality stability under permit banking. Therefore, many programs have applied the saving coefficients to restrict the amount of banked permits that can be carried for the future use. The study builds an economic model that does not require a systematic relationship among each saving coefficient to analyze how different banking rules might affect the environmental stability and total abatement costs in Taiwan. Using the Sulfur Oxide control in the Kao-hsiung and Ping-tung areas as an empirical example, the simulation results show that the proposed banking rules by Taiwan and the banking rules currently adopted by other countries all only have minor impacts on the environmental stability when the regulation standard is low. Thus, we should use the rules from the Acid Rain Trading Program which imposes no penalty on the banked permits to reach the lowest total abatement costs while offering the highest emission control flexibility at this stage. When the standards are more strict, we should follow the rules by the Emission Reduction Market System in Chicago which let the permits banked for only one year. It also implies that the current rules proposed by the Taiwan government do not perform well both in terms of the emission control flexibility and the environmental stability.