Abstract
Abstract. The International Maritime Organization (IMO) has moved to address the health and climate impact of the emissions from the combustion of low-quality residual fuels within the commercial shipping industry. Fuel sulfur content (FS) limits and an efficiency design index for future ships are examples of such IMO actions. The impacts of black carbon (BC) emissions from shipping are now under review by the IMO, with a particular focus on the potential impacts of future Arctic shipping. Recognizing that associating impacts with BC emissions requires both ambient and onboard observations, we provide recommendations for the measurement of BC. We also evaluate current insights regarding the effect of ship speed (engine load), fuel quality and exhaust gas scrubbing on BC emissions from ships. Observations demonstrate that BC emission factors (EFBC) increases 3 to 6 times at very low engine loads (<25% compared to EFBC at 85–100% load); absolute BC emissions (per nautical mile of travel) also increase up to 100% depending on engine load, even with reduced load fuel savings. If fleets were required to operate at lower maximum engine loads, presumably associated with reduced speeds, then engines could be re-tuned, which would reduce BC emissions. Ships operating in the Arctic are likely running at highly variable engine loads (25–100%) depending on ice conditions and ice breaking requirements. The ships operating at low load may be emitting up to 50% more BC than they would at their rated load. Such variable load conditions make it difficult to assess the likely emissions rate of BC. Current fuel sulfur regulations have the effect of reducing EFBC by an average of 30% and potentially up to 80% regardless of engine load; a removal rate similar to that of scrubbers. Uncertainties among current observations demonstrate there is a need for more information on a) the impact of fuel quality on EFBC using robust measurement methods and b) the efficacy of scrubbers for the removal of particulate matter by size and composition.
Highlights
The commercial shipping industry, through the United Nations International Maritime Organization (IMO), is subject to regulation on the quality of fuel that can be consumed within specially designated emission control areas (ECAs), in sensitive regions like the Antarctic, and globally (IMO, 2008, 2009)
It is apparent that for ships operating in the Arctic that are not involved in ice-breaking activities, engine loads are ≤40 % and as such black carbon (BC) emissions are larger than they otherwise would be for a re-tuned engine or an engine operating at higher loads
The International Maritime Organization (IMO) has begun to investigate the impacts of BC emitted from shipping activity and tasked an IMO subcommittee with providing more details on the definition of BC, measurement methods and possible strategies for BC mitigation
Summary
The commercial shipping industry, through the United Nations International Maritime Organization (IMO), is subject to regulation on the quality of fuel that can be consumed within specially designated emission control areas (ECAs), in sensitive regions like the Antarctic, and globally (IMO, 2008, 2009). There are a number of alternatives for reducing emissions from shipping, some of which have already been assessed for their efficacy and cost effectiveness (e.g. speed reductions, fuel quality, engine slide valves, water-in-fuel emulsions, fuel emulsions, particulate filters, exhaust scrubbers) (Corbett et al, 2009; Corbett et al, 2010b). There are three pathways that hold particular promise for emissions reductions; the effect of ship speed reductions (or ‘slow steaming’); fuel quality improvements; and exhaust scrubbers. We limit this review to the data available for marine diesel engines, and data available in peer-reviewed literature, industry reports and presentations that are in the public domain, or industry data where permission has been granted to publish the data
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