Gas is imported into Europe by two ways: through pipeline in gaseous form or alternatively it is liquefied, transported in vessels and finally regassified (LNG supply chain). These two chains differ not only from the physical and economical point of view, but also from the environmental one. In order to deliver the gas from the production fields to Europe, energy is required and its overall amount differs according to the way the gas is shipped. Furthermore other factors, like methane fugitives and nitrous oxide emissions, are affected not only by the physical characteristics of the chain, but also from the technology. The aim of this paper is to analyse from the environmental and economical point of view the global impact of the gas that enters into Europe, investigating the contribution of all the chain steps, starting from the production of the gas until the consumption in a power plant. Six different real cases are studied: three regarding a pipeline-based transport and three regarding LNG production, transport through tankers and regasification. Here summarized the main results:
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The average value of the chain emissions is around 13 kgCO2eq/mmbtu of natural gas imported (the emissions from the combustion of the natural gas is around 54 kgCO2eq/mmbtu)
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Along the supply chain the steps that give the most important contribution to the emissions are the treatment and the transport (pipeline and liquefaction+shipping)
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The emission of the treatment phase is mainly affected by the CO2 concentration in the raw gas (gas fields can have a CO2 content up to 14%mol)
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The emissions of the liquefaction and regasification process are strongly linked to the technologies installed that show a wide range of thermal efficiency.
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LNG tanker engine parameters (motor size, fuel, obsolescence) and performance of pipelines (pressure, diameter, leakages) are the main driver that impact the transportation step
