全球有90%以上的經貿往來透過海洋運輸完成，海運已堪稱是經貿往來的首選。國際商船進出港區皆須仰賴拖船來輔助進出港，拖船所使用的燃油消耗量佔近海船舶第三名，高達17%。拖船燃燒海運重柴油所致污染，包含NOX與SOX等，排放量分別佔全球航運15%與13%。頻繁的拖船作業造成的環境汙染，因此本論文研究以液化天然氣(LNG)作為船舶替代燃料之可行性。
本研究探討臺灣港務港勤公司，拖船輔助船舶進出港之情形，以EPA及SPB模式，探討拖船以LNG代替海運重柴油對環境之效益。實證分析結果為以EPA或SPB模式進行推估拖船汙染排放，若以LNG代替海運重柴油，將降低84-87%NOX、99%SOX、20-29%CO2及85-87%CO的汙染物排放量，顯示LNG對降低環境污染有明顯效益。為確保船舶安全進出港區，並達拖船排放汙染最小化原則，本研究並以最佳化模式進行汙染物推估並建議拖船調派之情境分析。研究結果指出，若進出港船舶總噸位10,000總噸，建議調派4,200馬力拖船1艘、進出港船舶總噸位20,000總噸，建議調派2,400及3,200馬力拖船各1艘、進出港船舶總噸位30,000總噸，建議調派3,200馬力拖船2艘、進出港船舶總噸位40,000-50,000總噸，建議調派3,200及4,200馬力拖船各1艘、進出港船舶總噸位60,000總噸，建議調派4,000馬力拖船1艘及4,200馬力拖船2艘、進出港船舶總噸位100,000總噸，建議調派3,200馬力拖船及4,200馬力拖船各2艘，將使得拖船汙染排放最小，並轉換船用燃料為LNG時，將可減少5.23%-5.86%的CO2e排放。

Nowadays over 90% of global trade relies on maritime transport which indicates its importance in terms of overall global economics and trade issues. When the international merchant shipping procedure highly depends on a tug, the fuel consumption of tug goes up by17% in offshore shipping, which is the third largest energy consumption. A Tug which uses Heavy Fuel Oils(HFOs) subsequently causes a lot of environmental pollution, such as NOX , SOX and so on. The contribution of the shipping emission to the global pollution can be identified as follows: nitrogen oxides(NOX ),15%、sulfur oxides(SOX ), 13%.The Tug operation has frequently been causing huge pollution Therefore the aim of this research is to study Liquefied natural gas (LNG) which has become the best choice for international shipping as an alternative fuel.
The aim of this research is to analyze TIPC marine corporations Ltd, whose tugs assist international merchant in and out of the harbor. And also explores the environmental influences of using LNG as an alternative fuel instead of traditional fuels which are based on EPA and SPB models. The result shows that by comparing LNG alternative to traditional fuels, the emission will reduce by 84-87% of NOX emission、99% of SOX emission、20-29% of CO2 emission and 85-87% of CO emission. In both examples the results show LNG has obviously benefited the environment. In order to ensure that the safety of ships coming in and out of the harbor, and achieve the principle of minimizing emission caused by the tugs, this research in the scenario analysis optimize mode estimates of the emission pollution and make recommendation of tug deployment. The results also show that TIPM should deploy the 10,000- ton ship with a 4,200ps tug, the 20,000-ton ship with a 2,400ps tug and a 3,200ps tug, the 30,000ton ship with two 3,200ps tugs, the 40,000-50,000- ton ship with a 3,200ps tug and a 4,200ps tug, the 60,000- ton ships with a 4,000ps tug and two 4,200ps tugs, the 100,000 ton ship with two 3,200ps tugs and two 4,200ps tugs. When LNG is alternative to traditional fuels, it will not only reduce the pollution to the least, but also reduce about 5.23% to 5.86% of CO2e emission.

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