Control measures of black carbon emissions from marine diesel engines - focus on results obtained using measurement methods selected by the IMO

Black Carbon emissions (BC) increase global warming, particularly in the Arctic region through deposition on ice and snow. Additionally, BC emissions adversely affect air quality and human health. The International Maritime Organization (IMO) is evaluating the needs for control of BC emissions from marine diesel engines. A number of researchers and experts worldwide contributed to the voluntary BC measurement programmes, and in the discussions of the results in the five BC Workshops organized by the ICCT (International Council of Clean Transport). This report evaluates control measures of BC emissions from marine diesel engines based on the results obtained using the measurement methods selected by the IMO.
LNG as a fuel for ships would lead to almost BC-free operations, and methanol is also a clean-combusted fuel. Very efficient BC removal could be obtained with particulate filters combined with clean marine distillate fuels, although their durability and long-term performance are yet to be proven. Oxygen-containing biofuels reduce BC emissions even without a particulate filter. When produced from renewable sources, methane, methanol and diesel-type fuels (combined with particulate filter) would cut both BC and GHG emissions. Hydrogen/fuel cells and batteries would enable BC-free shipping, however, these are not mature technologies for large ships today. Renewal or retrofitting the mechanical injection systems of old engines with modern fuel injection systems would reduce the BC emissions, as well as tuning engines to low BC emissions (combined with NOx reduction technologies). Modern engines would also enable the use of slow steaming without increased BC emissions from old engines. SOx scrubbers, diesel oxidation catalysts and EGR seemed ineffective in reducing the BC emissions, however, some integrated or tailored solutions are available.
In summary, BC reduction technologies are available for marine diesel engines, although they are not without challenges.