聯合國政府間氣候變遷專家委員會(Intergovernmental Panel for Climate Change, IPCC)指出,全球平均表面溫度持續升高,隨之而來的氣候變遷跡象將日趨顯著。而全球氣候逐漸變暖的現象有90%以上是因為人類活動導致溫室氣體濃度增加所致,其中二氧化碳是最主要的影響因素,而碳足跡可被定義為用以衡量經濟活動所產生或是產品的整個生命週期過程所累積直接與間接產生的溫室氣體總排放量,除此之外,各項資源匱乏的同時,水資源亦為生存之必要條件之一,其重要性不容小覷,台灣雖然雨量豐沛,但受限地形陡直與降雨季節分配不均,再加上地狹人稠,以致於每人可分配的水量不及世界平均值的 1/6,更為聯合國報告中的缺水國家。然而綜觀目前國內碳足跡評估之研究,多使用製程生命週期評估(Processes Based LCA, PLCA)產品、服務以及企業活動之碳足跡,鮮少針對消費行為及國家等尺度進行探討。緣此,本研究依據能源平衡表推估全國溫室氣體排放量,透過投入產出生命週期評估(Input output Life Cycle Assessment, IOLCA),將活動數據轉換成貨幣,來探討國內自來水供水系統產生一度水所需之碳足跡,評估傳統淨水處理之豐原給水廠供水系統及海水淡化系統之金門海水淡化廠供水系統供給民眾使用一度水所需之碳足跡,並與製程生命週期評估所得之結果進行比較。結果顯示使用IOLCA計算金門海水淡化廠之溫室氣體,以售水量表示為7.4692 kg CO2 eq/m3,以配水量表示則為5.1816kg CO2 eq/m3。PLCA計算可得以售水量表示為9.6305kg CO2 eq/m3,以配水量表示則為6.6809 kg CO2 eq/m3。用IOLCA計算豐原給水廠以售水量表示為0.0591 kg CO2 eq/m3,以配水量表示則為0.0367 kg CO2 eq/m3。PLCA計算可得以售水量表示為0.1942 kg CO2 eq/m3,以配水量表示則為0.1207 kg CO2 eq/m3。本研究推估因部份盤查資料不亦計算與分配,且水廠之原物料多為國外進口,貨幣單位與物理單位的轉換有困難度,導致兩種評估方法之結果有明顯落差。
Recent studies indicate that global warming is worsening, greatly affecting our environment. According to the Intergovernmental Panel of Experts on Climate Change (IPCC), average temperature is rising, seriously affecting our environment, and carbon dioxide (CO2) is one of the chief greenhouse gases responsible. Hence, the reduction of CO2 emissions is an important issue we need to respond to timely. Furthermore, water is the most essential element on earth. However, due to land formation and Taiwan's population, the estimated amount of Taiwan's utilized water only reaches one seventh of the world’s average. It shows that usable water resources in Taiwan are not fully utilized. In the past studies in Taiwan, Process-based Life Cycle Assessment (PLCA) is used to assess carbon footprint from products, organizations or activities, but seldom focuses on consumption behavior or country. Thus, this study uses Input-Output Life Cycle Assessment (IOLCA) to calculate Taiwan’s water supply systems. Two water purification plants, Kinmen Seawater Desalination Plant (KSDP) and FongYuan Water Treatment Plant (FYWTP) were studied, and results were compared to that of the PLCA for understanding the status of carbon footprint in Taiwan. The boundary of inventory and assessment includes the intake, the purification, and the distribution stages, as well as the infrastructure and the chemicals used that are associated with these stages. The IOLCA results show that the carbon footprints of the KSDP and FYWTP in water sold quantity are 7.4692 kg CO2 eq/m3 and 0.0591 kg CO2 eq/m3, in distributed water quantity are 5.1816kg CO2 eq/m3 and 0.0367 kg CO2 eq/m3. The PLCA results show that the carbon footprints of the KSDP and FYWTP in water sold quantity are 9.6305kg CO2 eq/m3 and 0.1942kg CO2 eq/m3, in distributed water quantity are 6.6809kg CO2 eq/m3 and 0.1207kg CO2 eq/m3.