本研究以生命週期評估及生命週期成本方法，探討塑木產品生命週期之環境衝擊議題與生態效益，環境衝擊議題包括能源消耗、溫室效應及其他環境衝擊類別。研究結果主要包含四部分，第一部分為個案產品生命週期評估，第二部分為碳足跡分析，第三部分為生命週期成本分析，第四部分為生態效益推估，第五部分為產品應用之減碳情境模擬，個案生命週期末端以回收處理而不採焚化處理之系統範疇，細部結果包括：(1)Eco-indicator 95評估結果，能源消耗以塑木(8.89MJ)最少，其次為木材(22.23MJ)；溫室效應以塑木(1.80kgCO2-eq.)較低，其次為PVC(5.76kgCO2-eq.)。(2)Eco-indicator 99評估結果在人類健康及生態品質方面以木材損害程度最大，資源方面以PVC損害最大，塑木三方面皆損害最小。(3)產品碳足跡分析以木材最高，塑木最低。(4)產品生態效益推估以塑木最優88.06NT$/kgCO2-eq.，木材最差1.27 NT$/kgCO2-eq.。(5)塑木替代木材應用於戶外甲板之減碳潛勢最高。 This study focused on the environmental impacts and eco-efficiency for WPC (Wood-plastic composites) by Life Cycle Assessment (LCA) and Life Cycle Cost (LCC). The results contained five parts, the first was LCA results and interpretation, the second was the carbon footprint results, the third was LCC analyses, the four was the eco-efficiency analyses, and the last was the scenarios for the carbon mitigation. The detailed results as following: (I)The Eco-indicator 95 results, the energy consumptions were 8.89MJ and 22.23MJ for the WPC and the wood, the greenhouse gases of WPC and PVC were 1.80kg CO2-eq. and 5.76kg CO2-eq. (I)The LCA results by Eco-indicator 95, the WPC energy consumtion was less with the value at 8.89MJ, and the next was the wood with the value at 22.23MJ; The greenhouse effect was less for WPC with the vale at 1.80kgCO2-eq., and the next was 5.76kgCO2-eq. for the PVC. (II)The Eco-indicator 99 results, the damages were higher on human health and ecosystem quality for the Wood, the PVC was higher on resources damage, and the WPC was less damage on the three damages. (III)The wood was the higest on the carbon footprint, and the WPC was less. (IIII)The WPC eco-efficiency was better than the others, and the less for wood. (V)The carbon mitigation protential was better by the WPC substituating for the wood.