Marine black carbon emissions: Identifying research gaps
Alyson Azzara, Dan Rutherford
This workshop was the first of three designed to inform and guide a new two-year project on marine black carbon funded by the Climate and Clean Air Coalition (CCAC). The project will develop a refined global marine black carbon (BC) inventory and technology performance database for mitigation strategies. The goal for this kickoff workshop was to refine the project work plan based upon a solid understanding of the current state of knowledge on BC measurement and testing, emissions inventories, and control strategies for marine vessels.
The workshop was held in Ottawa, Canada at the Environment Canada River Road Air Quality Laboratory. It included 35 in-person participants and multiple remote attendees, representing 21 organizations and 10 countries. The two-day agenda included seven sessions with 24 expert presentations on materials covering definition, measurement, and mitigation of black carbon, the state of the knowledge, gaps, and next steps for a research agenda.
Key workshop outcomes included a consensus definition of marine black carbon for research purposes, next steps for aligning diagnostic approaches (appropriate measurement and sampling protocols), and four main recommendations for priority research.
Regarding black carbon definition, participants agreed to use the definition of black carbon proposed by Bond et al (2013) for climate research purposes. Measurement methods linked to the light absorbing and refractory properties of black carbon were considered to be most consistent with this definition, although the value of parallel testing with other methods was also recognized. Support was also expressed for establishing minimum performance requirements for appropriate instrumentation methods. Given the high sulfur content of current marine fuels, the establishment of standardized pre-treatment protocols to remove volatile fractions was recommended to facilitate the comparisons of results
Fuel switching, scrubbers, filters (where available), and slow steaming were identified as priority control strategies for investigation. An additional outcome identified was the need to refine BC marine inventories through coordinated research on baseline emission factors using some combination of on-board, test bench, and plume studies of marine vessels.
Near term research steps include:
- A comprehensive review of existing emission factors
- A vessel activity and fleet composition review to identify key sources (i.e. ship/engine types, operational conditions, etc.) not yet characterized
- A focused discussion and research plan to evaluate diagnostics (i.e. measurement instrument protocols and sample pre-treatment)
- An analysis of the relative merits of on-board measures, test bench analyses, and plume studies research for inventory development and evaluation of control strategies
All parties agreed to continuing work facilitating the sharing of information and to developing an inclusive research approach.