SOx許可交易方案之成本效益及風險

Abstract

空氣污染排放許可交易為一個有效且具經濟誘因的污染防治制度，其以市場誘因引導污染減量及技術提升，有助於達成兼顧經濟和環境保護的目標，因應國內研議可交易空氣污染排放許可制度(ETP)之決策分析需求，本研究分析及評估可交易許可策略在國內施行的可能成本效益及風險，以供相關決策參考。本研究依據邊際防治成本及隨機方式建立交易行為模擬模式，交易前後之空氣品質變化乃是以ISC模式模擬推估之，風險除了依據法定標準來評估空氣品質風險外，亦依據人口曝露量及損害函數來評估之，且針對交易後風險高的案例，測試以抵換制度降低風險的效率。本研究以桃竹苗空品區資料建立四個研究案例，分別模擬獨占性、非獨占性及考量不參與交易小污染源的市場，依據所建立的ETP交易行為模式模擬交易結果及其在各案例之可能之成本效益與風險。交易模擬結果顯示，交易後之總金額約在24-52億元及成本效益約為24-46億元間，主要是受到可交易許可量、邊際成本差、交易價格及交易次數所影響。有關風險部分，在交易後，有大型排放源之案例，由於許可交易至人口密度較高區，導致有污染物濃度人口曝露量及損害風險度升高的情況，而沒有大型的排放源的案例，則由於許可集中至一些區域，在污染量集中所產生的peak effect，導致空氣品質不合格率升高，在分別採用人口差及距離差的抵換制度後，可降低這些風險。不過，在四個案例ETP模擬結果顯示交易後的風險均較想像中低；即使交易後空氣品質、曝露或損害風險有時會提高，但若配合適當的抵換(offset)或其它制度來降低風險，故ETP仍為一值得執行的政策。

Emission trading program (ETP) is an effective economic incentive policy for pollution abatement. A proper market-based ETP can effectively promote pollution reduction and technology advance, thereby harmonizing the conflict between economical development and environmental protection. Various national air pollution control policies and bubble strategies were implemented and planed in recent years. To support the decision-making analysis for an appropriate domestic emissions trading program (ETP), this study analyzed and assessed the potential cost effectiveness and air pollution risk of an ETP. Trading behaviors were simulated based on a marginal cost difference and a random approaches. Ambient air qualities before and after the trading were simulated by the ISC model. Air pollution risk was defined based on the ambient standard, a population exposure index, and two types of damage functions. For those scenarios with risk being increased after the trading, an offset policy was applied to reducing the risk. Four varied scenarios based on the data collected for the Tao-hsu-mao airshed were established to simulate monopoly, non-monopoly, and typical markets for evaluating the cost effectiveness and pollution risk under varied markets, using the proposed simulation approaches. According to the simulation results, the total trading cost and saving are about NT$ 2.4-5.2 and 2.4-4.6 billion, respectively. The scenarios with few significantly large emission sources, population exposure and damage potential are both increased after the trading because pollution permits are transferred from a low population density area to a high density area. On the other hand, for scenarios without large sources, the air quality violation ratio may be increased after the trading because pollution permits are transferred into several small areas and thus concentrate the emission and induce some peak effects. These risks can be reduced by an offset policy based on population density difference or distance. However, the risk increased after the ETP trading is not significantly large for four simulated scenarios. Even though it is possible to increase the risk, a proper offset or other policy can be applied to reduce the risk. A proper ETP should be an attractive policy for environmental authority to implement. This study collected information for various ETPs and associated experiences. A systematic procedure with development of mathematical and optimization models was proposed for assessment of potential benefit, effectiveness, and ambient air quality risk of a ETP. The ETP decision-making analysis is expected to be improved based on the proposed procedure, and hopefully an appropriate ETP can be designed and implemented. Emissions trading is a market-incentive pollution reduction approach that has been adopted by several foreign countries. A proper ETP is expected to resolve the conflict between the economic development and environmental protection and to increase pollution dischargers’ incentive to adopt efficient pollution control technologies and therefore effectively achieve the pollution reduction goal.