Black carbon from ships: a review of the effects of ship speed, fuel quality and exhaust gas scrubbing D. A. Lack1,2 and J. J. Corbett3 1Chemical Sciences Division, Earth System Research Laboratory, NOAA, Boulder, Colorado, USA 2Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA 3College of Marine and Earth Studies, University of Delaware, Newark, Delaware, USA
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.
Citation: Lack, D. A. and Corbett, J. J.: Black carbon from ships: a review of the effects of ship speed, fuel quality and exhaust gas scrubbing, Atmos. Chem. Phys., 12, 3985-4000, doi:10.5194/acp-12-3985-2012, 2012.