Abstract
The shipping industry is looking for strategies to comply with increasingly stringent emission regulations. Fuel has a significant impact on emissions, so a switch to alternative fuels needs to be evaluated. This study investigated the emission performances of liquefied natural gas (LNG) and liquefied biogas (LBG) in shipping and compared them to conventional marine diesel oil (MDO) combined with selective catalytic reduction (SCR). For assessing the complete global warming potential of these fuels, the life-cycle approach was used. In addition, the study evaluated the local environmental impacts of combustion of these fuels, which is of particular importance for short sea shipping operations near coastal marine environment and residential areas. All three options examined are in compliance with the most stringent emission control area (ECA) regulations currently in force or entering into force from 2021. In terms of local environmental impacts, the two gaseous fuels had clear advantages over the MDO + SCR combination. However, the use of LNG as marine fuel achieved no significant CO2-equivalent reduction, thus making little progress towards the International Maritime Organization’s (IMO’s) visions of decarbonizing shipping. Major life cycle GHG emission benefits were identified by replacing fossil fuels with LBG. The most significant challenge facing LBG today is fuel availability in volumes needed for shipping. Without taxation or subsidies, LBG may also find it difficult to compete with the prices of fossil fuels.
Highlights
Reducing ship emissions and developing the sector in an environmentally friendly manner has been the subject of the regulatory framework for years
This study investigated the emission performances of liquefied natural gas (LNG) and liquefied biogas (LBG) in shipping and compared them to conventional marine diesel oil (MDO) combined with selective catalytic reduction (SCR)
LBG’s TTP phase greenhouse gas (GHG) emissions mainly are caused by methane slip from the dual-fuel engine, and to a minor extent from fossil CO2 emissions originating from the MDO pilot fuel
Summary
Reducing ship emissions and developing the sector in an environmentally friendly manner has been the subject of the regulatory framework for years. The Baltic Sea was designated a Sulphur Emission Control Area (SECA) in 1998, and the current fuel sulfur content limit of 0.1% came into force in 2015 [1]. In July 2017, the IMO’S Marine Environment Protection Committee (MEPC) designated the Baltic Sea a NOx Emission Control Area (NECA), effective from 1 January, 2021 onwards [2]. NECA regulation (Tier III) applies to all vessels built after 2021 and demands an 80% cut in NOx emissions compared to the present emission level. This means new-builds either will have to be equipped with a proper exhaust after-treatment system for NOx reduction, or use liquefied natural gas (LNG) as fuel to comply with the regulation. There are concerns about health risks associated with particle emissions from shipping, so regulations focused on particulates may be expected in the future [3]
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