應用空間特殊性生命週期評估於台灣PVC供應鏈之環境衝擊與環境債分析

Abstract

我國為全球PVC主要生產與出口國之一，為了釐清因國內PVC使用或外銷需求所衍生之跨國環境債問題，本研究針對PVC跨國生產鏈之各主要原料供應國進行生命週期盤查，並搭配產量進行境內與境外排放之分配，再藉由生命週期衝擊評估模式分析境內與境外之衝擊型態。另一方面為了瞭解上游製程更新對國產PVC之整體環境效益，本研究選擇電力與乙烯生產這兩個主要衝擊熱點，進行CHP技術更新與乙烯能源效率提升之衝擊減量效果分析。 2008年，國產PVC產量約138萬噸,其中直接出口約79萬噸。剩下用於國內生產下游產品之59萬噸PVC中,又有約10萬噸出口至其他國家,剩下49萬噸為實際之國內PVC需求。故國產PVC與其下游產品於國內使用之比例為35%,國外使用之比例為 65%。 根據基線年之評估結果，國產PVC總共造成11700 DALYs的人體健康損害與5.12物種×年之生態系損害。其中人體健康損害貢獻度依序為電力需求(48%)、其他能源使用(23%)、乙烯生產(15%)、原油開採(11%)等，而生態系損害之趨勢亦雷同。若以衝擊類別而言,氣候變遷為人體健康損害之主要來源(77%),其次為懸浮微粒生成(13%)與人體毒性(10%)。故以製程而言，電力、其他能源與乙烯生產過程為國產PVC之環境熱點。在汙染物方面，溫室氣體為主要貢獻源，而國內排放佔了91%,其中又以境內電力所貢獻之50%為首。 在技術更新的部分，衝擊減量效果最顯著者為國內製程之CHP更新(未包含乙烯製程),其在人體健康與生態系損害方面分別較基線年降低15%與10%。其次依序為中油輕裂廠CHP更新(人體健康減7%、生態系減8%)、中油輕裂廠製程更新(人體健康減4%、生態系減5%)、台塑輕裂廠CHP更新(人體健康減3%、生態系減4%)。若四種技術更新情境同時實行，將產生3413個DALYs的健康效益(減量 29%)與 13.64物種×年之生態效益(減量27%)。 結合境內外衝擊分析與國產PVC流向後，可將我國PVC環境債區分為以下三類(1)境內衝擊-國內使用:台灣每年承受474個DALYs之健康損失與0.04個物種×年之生態損害以生產PVC供國內使用。(2)境內衝擊-國外使用(台灣為債權國):台灣每年承受880個DALYs之健康損失與0.075個物種×年之生態損害以生產PVC供他國使用。(3)境外衝擊-國內使用(台灣為債務國):國外每年承受439個DALYs之健康損失與0.009個物種×年之生態損害以生產PVC上游原物料供台灣生產PVC自用。值得注意的是，全球共同承受之全球尺度衝擊雖無法區分為境內或境外，但其損害量大幅超越區域性衝擊,達到8596個DALYs與48.686物種×年。

Taiwan is one of the main PVC producer and exporter in the world. In order to inspect the ecological debt of Taiwan made PVC induced by multi-national supply chain and consumption location, this research collects the inventory data from main supply contries of Taiwan-made PVC (cradle to gate) and allocates the domestic/overseas emissions by the ratio of Taiwan-made or imported raw materials. Via the combination of life cycle impact assessment, we could then evaluate the traits of domestic/overseas environmental impacts of Taiwan-made PVC quantitatively. In addition, with the purpose to understand the impact reduction potential via process renewal, electricity & ethylene production were choosen to set several policy scenarios as they are the main impact contributors (hotspots) during the PVC manufacturing process in Taiwan. In 2008, Taiwan produced 1.38 Mt of PVC, among which 0.79 Mt were directly exported. In the remaining 0.59 Mt of PVC, 0.1 Mt were processed into final products and exported, the other 0.49Mt were the actual PVC demand in Taiwan. Overall, 35% of Taiwan made PVC were used domestically, and 65% of PVC were for exporting purpose. Based on the LCIA result of baseline year, Taiwan-made PVC contributed 11700 DALYs of human health damage & 5.12 species loss of ecological damage in 2008. Where electricity consumption(48%), other energy consumption(23%), ethylene production(15%), crude oil extraction(11%) are the main contributors in human health damage, where the trends in ecological damage is consistent with human health damage. In terms of human health damage contributions from each impact category, climate change stands for the highest impact(77%), followed by particulate matter formation(13%) and human toxicity(10%). Furthermore, the main substances responsible for environmental damages of PVC measured from cradle to gate are green house gases, in which 91% emitted domestically and mainly from electric generation. Regarding to the reduction potential of process renewal , CHP renewal from domestic processes (exclude ethylene production) is most prominent with a reduction potential of 15% in human health & 10% in ecological damage compared to baseline. Followed by CPC cracker’s CHP renewal (7% in human health, 8% in ecological damage), CPC cracker renewal (4% in human health, 5% in ecological damage), Formosa cracker’s CHP renewal (3% in human health, 4% in ecological damage). Collectively bring forth to a reduction of 3413 DALYs (29% reduction) and 13.64 species loss (27% reduction). By integrating domestic/overseas impact assessment and PVC flow analysis, we can then divide the ecological debt into three categories: (1)Domestic impact-Domestic consumption: Taiwan bears 474 DALYs & 0.04 species loss to produce PVC for domestic use (2)Domestic impact-Overseas consumption: Taiwan bears 880 DALYs & & 0.075 species loss to produce PVC for overseas use (3)Overseas impact-Domestic consumption: Other foreign countries bear 439 DALYs & 0.009 species loss to produce raw materials for Taiwan-made PVC which consumpted domestically. Be worthy of note, global scale impacts like climate change cannot be divided into domestic/overseas impacts, but actually predominant the total human health or ecological damage, reaching 8596 DALYs & 48.686 species loss in baseline year.