以生命週期盤查法估算臺灣人工林人為施業之溫室氣體排放

Abstract

近年來全球氣候變遷對環境、人類及生態造成眾多影響，促使各國重視此議題，並訂立2050年淨零碳排目標。為減少因人為所產生之過量溫室氣體，以自然為本之造林為各界所仰賴；然而，造林活動除林木之固碳作用外，亦會因一定之機具使用或活動而產生溫室氣體排放。因此，本研究回顧國內外文獻及訪談國內相關林業單位於原木生產前各階段之人為施業與經營措施可能產生之溫室氣體排放，整理並歸納計算方法，以生命週期盤查法估算臺灣森林經營從育苗到收穫之溫室氣體排放，並建立溫室氣體排放參照表與溫室氣體盤查紀錄表，以利國內林業經營者檢視與計算不同階段人為施業活動之溫室氣體排放量。根據訪談國內林業單位所得之資訊，估算臺灣人工林森林經營過程中人為施業所產生之溫室氣體排放量約為 8578.7-10021.9 kg CO2e/ha，而國外研究之原木生產過程中人為施業所產生之溫室氣體排放量約為7083.4-19155.1 kg CO2e/ha，且商業性伐採階段的溫室氣體排放量高於最終伐採階段；比較國內外使用鏈鋸機伐採和怪手集材整堆造成的溫室氣體排放量，臺灣林業經營亦高於國外研究所提供之數據結果。推測造成差異之可能原因為臺灣地勢環境過於崎嶇，或是相關伐採法規之限制。在環境限制與法規未改變之情況下，未來若要減少臺灣森林經營時因人為施業所產生之溫室氣體排放量，以使用再生能源或提升機具之使用效率為較可行之方案。本研究亦建議未來應建立林業生產活動相關之公開資料庫，以促進相關研究發展並推動永續森林經營與利用。

In recent years, global climate change has caused numerous impacts on the environment, humans, and ecosystems, prompting countries to respond to this issue and set a net-zero carbon emissions target by 2050. To reduce excessive greenhouse gas emissions caused by human activities, afforestation based on natural principles, is relied upon by various sectors. However, aside from the function of carbon sequestration from afforestation activities, the use of certain machinery or practices associated with afforestation can also result in greenhouse gas (GHG) emissions. Therefore, this study reviewed domestic and international literature and interviewed relevant forestry organizations in Taiwan to estimate the potential GHG emissions associated with activities and management measures during the stages before timber production. This study organized and summarized calculation methods and established a GHG emission inventory for Taiwan's forest management activities from seedling cultivation to harvest using a life cycle inventory method. Following that, a reference table and a record table for GHG emissions inventory were provided for domestic forestry operators to examine and estimate the associated GHG emissions during different forest management activities. According to the information obtained from interviews with the domestic forestry organizations, the estimated GHG emissions from the plantation management activities and anthropogenic practices in Taiwan were approximately 8578.7-10021.9 kg CO2e/ha. In contrast, foreign studies reported GHG emissions from the log production process due to activities in the range of 7083.4-19155.1 kg CO2e/ha. The commercial harvesting stage had higher GHG emissions than the final harvesting stage. Comparing the GHG emissions caused by chainsaw logging and mechanized harvesting and stacking between domestic and foreign studies, the forestry operations in Taiwan also yield higher emissions than the data provided by the international practices from the literatures. The differences may be attributed to Taiwan's rugged terrain and restrictions imposed by relevant logging regulations. In the future, under the constraints of environmental limitations and regulations, to reduce GHG emissions raised during Taiwan's forest management stages, the use of renewable energy and improving the efficiency of machinery usage may be more feasible solutions. Establishing publicly accessible open database associated with forestry production activities is also suggested to promote forestry research and sustainable forest management and utilization in the future.