台灣工業部門二氧化碳之排放減量成本：環境方向性距離函數之應用

The Abatement Costs of CO2 Emission in the Industrial Sectors in Taiwan - The Evnironment Directional Distance Function Approach

過去有關溫室氣體減量成本之學術文獻，大都是採用可計算一般均衡模型去評估特定減量目標下所需付出的總體經濟成本，不過在計算過程中常因參數設定不同而有不同的估計結果。如果我們從生態效率的觀點來看，若廠商在減少能源使用與二氧化碳排放之際，又能夠增加意欲產出，則是經濟成長與環境保護的雙贏局面。因此，不同於過去文獻，本文嘗試以環境方向性距離函數，利用2005-2010 年我國工業部門14 個產業中，365 家上市櫃、興櫃和公開發行公司的資料，探討各個產業的生態效率水準並估算管制CO2 排放量所產生之平均減量成本。
根據本文的研究結果，政府若使用強制的政策工具以限制產業CO2 的排放，或廠商對自己的生產活動進行自願環境管理，那麼生態效率的水準則會較高。此外，透過環境方向性距離函數所衡量的生態效率結果來看，從強可棄置性的無管制技術到弱可棄置性的有管制技術，水泥及水泥製品業都是較無生態效率的產業；也就是說，水泥業本身是個高污染的產業，縱使管制其CO2 的排放量，生態效率的改善亦是有限。因此，雖然關閉國內生產線而外移境外是一選擇，但因碳漏損風險的可能以及對產業的影響層面過大，因此尋求新技術的提升或許是目前較務實的作法。最後，雖然賦予廠商減排責任的確可以提升生態效率水準，但廠商因而造成意欲產出的減少或其面對的機會成本是否過高，亦是一個不可忽視的問題。

The computable general equilibrium (CGE) model is typically used to estimate the economic costs of reducing greenhouse gas emissions in previous studies. However, the CGE model is subject to the specified parameters, and it usually focuses on macro-level estimation. From the eco- efficiency perspective, a firm that can reduce energy use and carbon dioxide (CO2) emissions but also increase the desired output can contribute to both economic growth and environmental protection. Thus, unlike previous works, this study uses the environmental environment directional distance function so that firms can increase good outputs and reduce bad outputs simultaneously. The estimated impacts and abatement costs of CO2 emissions in Taiwan are based on 2005-2011 data for 365 firms in 14 industries.
The empirical results confirm that eco-efficiency can be substantially improved if the government executes compulsory policies or a firm voluntarily controls its CO2 emissions. In addition, no matter the strong or weak disposability assumption is applied in the estimation, cement manufacturing is an ecologically inefficient industry. Thus, stopping domestic production is one option, but it may cause the carbon leakage and also influence domestic industries severely. Therefore, seeking new technologies to reduce pollution may be a pragmatic alternative. Finally, holding firms responsible for emissions reductions can indeed improve eco-efficiency but the excessive opportunity cost is a problem that cannot be ignored.