SCRUBBERS
CONFLICTING VIEWS One new report recommends banning scrubbers entirely while another finds that the carbon footprint of using a scrubber is lower than that of low-sulphur fuels
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study published by environmental campaign group International Council on Clean Transportation (ICCT) recommends that IMO should consider banning the use of exhaust gas cleaning systems (EGCS), or 'scrubbers', on newbuild ships and phasing them out on existing ships. The ICCT report says the number of ships using exhaust gas cleaning systems has grown from just three ships in 2008 to more than 4,300 in 2020. It argues: “Although scrubbers are effective at reducing air emissions of sulphur dioxide (SO2), the sulphur and other contaminants removed from the exhaust gas—including carcinogens such as polycyclic aromatic hydrocarbons (PAHs) and heavy metals—are dumped overboard in the form of washwater, also called discharge water. Meanwhile, the International Maritime Organization’s (IMO) guidelines for scrubber discharges have not been strengthened since 2008,
despite being reviewed in 2009, 2015, and 2020, and the guidelines ignore the cumulative effects of many ships operating and discharging in heavily trafficked areas. Such cumulative effects are to be expected given the rapid increase in the number of ships with scrubbers.” The ICCT study says that SO2 emissions from ships using 2.6% sulphur HFO with a scrubber are on average 31% lower than ships using 0.07% sulphur MGO. Particulate matter emissions are nearly 70% higher using HFO with a scrubber compared with MGO. Black carbon emissions are 81% higher using HFO with a scrubber than using MGO in a mediumspeed diesel engine and more than 4.5 times higher than using MGO in a slow-speed diesel engine, according to the study.
ICCT argues that scrubbers are therefore not equivalently effective at reducing total air pollution emissions compared to using MGO. Additionally, its study says direct carbon dioxide (CO2) emissions are 4% higher using HFO with a scrubber compared to MGO, and even though HFO has lower upstream emissions than MGO, the extra fuel consumption associated with powering the scrubber results in 1.1% higher CO2 emissions on a life-cycle basis when using HFO. Regarding water emissions, the study finds scrubber discharges typically comply with IMO guidelines, but all scrubbers— open-loop, closed-loop, and hybrid—discharge water that is more acidic and turbid than the surrounding water. ICCT says this contributes to ocean acidification and worsens water quality.
CO2 emissions associated with the production of low-sulphur marine fuels will be between these extreme values. ©CE Delft
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World Bunkering WINTER 2020/21