應用氣候變遷情境探討糧食、能源與水鏈結之最佳化：以殘餘生質物產製生質能源為例

Optimization in food, energy and water nexus applying climate change scenario: a case study of bioenergy generated from residual biomass

袁光宇(Kuang-Yu Yuan)

指導教授 ： 闕蓓德

國立臺灣大學/工學院/環境工程學研究所/碩士(2017年)

https://doi.org/10.6342/NTU201701649

摘要

隨著全球人口增長及社會經濟成長，糧食、能源及水資源安全議題的重要性 也隨之上升。此外，國際上對於此三種資源的研究也從彼此獨立，逐漸發展至探 討其交互的關係。因此，發展考量其交互關係之評估架構與方法成為現今相當重 要的研究議題。
傳統作物種植往往耗費大量水資源及占用土地。此外，除了種植過程本身的 資源耗用，在製造作物種植所需的物料的過程中，也耗用許多能源。而若資源使 用效率不佳，更將造成額外的環境衝擊。為增加作物種植的資源使用效率，並減 少環境衝擊，本研究以利用農業殘餘生質物產製生質能為研究主軸，希冀尋求對 環境負面影響最小的解決方案。然而使用生質能的實際效益將依區域特性而有所 不同；全球氣候變遷也將對農業水資源的使用與分配造成影響。為解決上述問題， 本研究建立一從環境角度出發的評估工具，以土地因子作為研究核心，綜合考量氣候變遷情境下，糧食、能源與水資源使用等條件的變化以及區域特性，改變稻米、玉米及甘蔗之種植面積，尋求最佳的作物種植配置。本研究利用生命週期評估計算環境衝擊，並利用氣候變遷模式模擬未來灌溉用水量之變化，最後以最佳化方法綜合討論生質能源生產之發展。在此最佳化系統中，環境衝擊減少量的最大化為求解目標，作物的種植面積為決策變數，同時考量水資源使用量、糧食供給量、可耕地面積等作為限制條件。
結果顯示，稻米的種植所造成的環境衝擊遠大於玉米及甘蔗種植所帶來的衝擊。產製生質能源部分，利用稻稈焙燒製造出之生質炭與煤炭混燒發電，在四項損害類別的表現皆 優於傳統燃煤發電；以玉米桿產製之纖維素酒精汽油與傳統無鉛汽油混配，其環境效益也大於傳統汽油；以甘蔗渣產製之纖維素酒精混配無鉛汽油雖也能產生環 境效益，但其環境表現略遜於玉米桿產製之酒精汽油。考量上述環境衝擊及氣候變遷對於灌溉可用水量的變化後，最佳化結果顯示，由於稻稈產製之生質炭發電 能帶來最高的環境效益，因此在滿足水資源限制條件下，稻米的種植越大，能對整體帶來更大的環境衝擊減量效益。在空間分布部分，因為區域種植特性的不同，建議原本種植於中部與東部的玉米能集中至南部。本研究考量生命週期評估結果與 IPCC所提供之氣候變遷情境，以永續環境發展為目標，能提供決策者一系統性的評估方法，並針對未來的糧食、能源及農業用水政策給予建議。

關鍵字

糧食能源與水之鏈結 ； 生命週期評估 ； 氣候變遷 ； 最佳化

並列摘要

Along with the continuously increasing demand for services, the problem of food, energy and water security is of raising significance. The nexus representing these three resources are interconnected with each other. Consequently, there is a need to develop an assessment framework and methodology considering the interrelationships. Crop cultivation usually accounts for large amounts of water consumption and land occupation. In addition, it also consumes many energy during the cultivation and raw materials production. Besides, a high degree of inefficiency in water use and energy inputs leads to additional environmental impact as well. In order to increase the efficiency of crops cultivation and reduce environmental burden, converting biomass from the agricultural residues into bioenergy is considered as a way to sustainable development. Nevertheless, the real benefit is still unclear due to different regional situation; the influence of climate change also causes the uncertainty on water availability. Due to these defects, it is necessary to develop a comprehensive assessment system considering environmental impacts. The objective of this study is to address an integrated optimization model that integrates life cycle assessment and climate change simulation. This optimization model is able to provide an environmental assessment for bioenergy production, and climate change simulation for irrigation water requirements estimation. The objective functions in the optimization model is to maximization the amount of environmental impact reduction under multiple constraints. The use of water resources, the demand for food supply and area of arable land are considered. The result indicates that the rice cultivation caused the most severe environmental impact comparing with corn and sugarcane cultivation. As for bioenergy, co-firing hard coal with bio-coal is of benefit on all four damage categories (i.e., human health, ecosystem quality, climate change and resources). Gasohol blended with corn stover-based cellulosic ethanol is of benefit among four categories as well while that blend with sugarcane bagasse-based cellulosic ethanol will cause more impact than corn stover-based ones. Considering the change on irrigation water availability, the optimal results indicates that the rice cultivation should be reduced to achieve water resources limit in some scenarios, and is supposed to increase within the limit of water resources. The corn and sugarcane cultivation in eastern region should be switch to southern region under all scenarios. This study provides decision makers an instruction to develop agriculture and energy strategies regarding both resource use efficiency and environmental impact.

並列關鍵字

Food-energy-water nexus ； Life cycle assessment ； Climate change ； Optimization

參考文獻

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