能源與資源的匱竭，以及由於過多溫室氣體產生之氣候異常現象，已經是現今世界最受矚目的議題。天然資源不足的臺灣，加上日趨嚴重的全球暖化問題的浮現。臺灣身為地球公民的一份子，也正在積極尋找與發展自產能源及創造低碳社會。
本研究有三個目的：首先，使用生命週期評估的觀念，去評估在臺灣以甘蔗為原料製造之酒精的溫室氣體排放量；接著，應用敏感度分析去釐清哪些因子對於酒精生產的溫室氣體排放最具影響力；最後，應用情境分析去計算臺灣自產酒精燃料的潛力，以及溫室氣體的排放情況。
在甘蔗生產部分，本研究評估三年為一個循環的甘蔗作物系統。當一噸的原料甘蔗被生產時，會有248和107公斤二氧化碳當量的溫室氣體排放，分別對應使用階層一（Tier 1）和階層三（Tier 3）方法計算的土壤排放量。而在二氧化碳吸收的部分，一噸的原料甘蔗將可以吸收386公斤二氧化碳當量的大氣中之二氧化碳，因此，一噸的原料甘蔗生產時，其淨溫室氣體排放量是負的。在酒精生產部分，當一公升的無水酒精生產時，會有4.42公斤二氧化碳當量的溫室氣體排放。當甘蔗生產和酒精生產的流程一起被考慮時，主要的溫室氣體排放來源是酒精生產的電力產生程序、土壤、肥料生產製程、甘蔗生長過程和糖蜜發酵過程，分別佔全部排放量的百分之50.8、23.1、11.1、3.4和3.0。對於溫室氣體而言，一氧化二氮和二氧化碳分別在甘蔗生產和酒精生產的程序中，貢獻最多的全球暖化潛力。
由甘蔗生產的敏感度分析可知，甘蔗的產量改變時，造成結果的變動最大。而其次是肥料的使用量，尤其是氮肥。而從甘蔗生產和酒精生產的敏感度分析指出，我們可以藉著增加糖蜜離心分離、甘蔗產量、酒精轉化、蒸氣生產、鍋爐和蒸氣生產電力等的效率，和提高蔗渣的熱值，以及淨蔗和糖蜜中的蔗糖含量，去顯著的降低每單位無水酒精生產時的溫室氣體排放。根據敏感度分析得知，每噸原料甘蔗和每公升無水酒精生產時的溫室氣體排放，將分別落在54.4-111.4和3.68-5.16公斤二氧化碳當量。在本研究中，完成了排放等高線（level line）的輔助決策工具，其主要的訊息為：如何在不增加溫室氣體排放的情況下，改變農業活動（例如，灌溉、施肥和耕作）的條件。
根據情境分析的結果得知，臺灣自產酒精燃料將可以達到政府訂定的酒精燃料發展目標，且溫室氣體的淨排放為負。更進一步來說，臺灣以甘蔗為原料製造之酒精，具有發展再生能源和達到低碳社會的潛力。

Depletion of resources for energy and materials, and climate change caused by greenhouse gas (GHG) are among the most concerned sustainability issues in world. In Taiwan, natural resources for materials and energy are limited and adverse consequences induced by the climate change as a result of the global warming phenomena. As a local resident as well as a global citizen; Taiwan is seeking for its way towards the two sustainability objectives: development of indigenous resources and lower carbon society.
There are three objectives in this study: (1) to evaluate GHG emissions induced from ethanol fuel produced from sugarcane in Taiwan using the concept of life cycle assessment (LCA), (2) to apply sensitivity analysis to understand the information of sensitivity in the model for further applying our model to other conditions, and (3) to apply scenario analysis to understand the potential of ethanol produced from sugarcane and their consequences in GHG emission changes in Taiwan.
A 3-year cycle of sugarcane cropping system is applied in this study. The GHG emissions associated with sugarcane production in Taiwan are 248 and 107 kg-CO2-equiv. per ton of raw sugarcane production when the Tier 1 and 3 methods are applied to calculate the land use emissions. With regard to the atmospheric CO2 absorption, 1 ton of raw sugarcane is able to absorb 386 kg-CO2-equiv.; therefore, the net GHG emissions are negative when 1 ton of raw sugarcane is produced. The GHG emissions are 4.42 kg-CO2-equiv. per L of absolute ethanol produced. When the sugarcane and ethanol production processes are integrated, processes of power generating (P20), soil, fertilizer manufacturing (P5), sugarcane growing (P2), and fermenting (P15) are the main sources of GHG emissions, and which are accounted for 50.8, 23.1, 11.1, 3.4, and 3.0 % of total GHG emissions. Among the GHG, N2O and CO2 contribute the most global warming potential in sugarcane and ethanol production processes, respectively.
The results of sensitivity analysis for sugarcane production indicates that the result is most sensitive to the changes in parameters related with yields of sugarcane in new planting and ratoon cultivations. To change the fertilizers consumption, especially for nitrogen fertilizer, also leads more sensitive results. According the results of sensitivity analysis for sugarcane and ethanol production, the GHG emissions from 1 L of absolute ethanol are able to be reduced more by increasing the efficiency of centrifugal separating, sugarcane production, ethanol converted from molasses, steam production, boiler, and electricity generated by steam, heat value of bagasse, and sucrose content in clean sugarcane and molasses. The GHG emissions could vary within the range of 54.4-111.4 kg-CO2-equiv. per ton of raw sugarcane and 3.68-5.16 kg-CO2-equiv. per L of absolute ethanol production when one-at-a-time (OAT) method is applied. Emission level lines were developed aiming at supporting decisions about modifying agricultural methods (ex. irrigation, fertilization, and tillage) that should be made considering consequential changes in GHG emission.
According to the scenario analysis, we can understand that ethanol from domestic sugarcane can reach the target of ethanol fuel development, and the GHG emissions are negative. Furthermore, ethanol produced from sugarcane in Taiwan has the potential to achieve the goals of development of materials and renewable energy, and low carbon society.

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