- David Loosley
Black Carbon (BC) is the name given to solid particles emitted during incomplete combustion and is also referred to as ‘soot’, ‘elemental carbon’ and ‘graphite carbon’.
Diesel engines are an important source, though not the major one, which is combustion of fossil. BC contributes to climate change in two ways – first, in the atmosphere where it absorbs sunlight and re-emits the energy as heat. Secondly, when deposited on ice or snow, in addition to warming the surface and air directly, it reduces the surface reflectivity (albedo), causing it to absorb more sunlight.
BC is regarded as second only to CO2 in terms of climate change. Because it is short-lived, remaining in the atmosphere only a few weeks, redcuing BC emissions could have a very rapid and significant effect on the rate of warming. BC is also a serious public health concern. Exposure to particulate matter is responsible for hundreds of thousands of deaths globally each year.
The 62nd session of the International Maritime Organization’s Marine Environment Protection Committee (MEPC), held 11 – 15 July 2011 addressed the increasingly topical issue of BC, adopted a work plan to address the impact on the Arctic of emissions of BC from international shipping.
At the time MEPC instructed the Sub-Committee on Bulk Liquids and Gases (BLG) to: develop a definition for BC emissions from international shipping; consider measurement methods for BC, and to identify the most appropriate method for measuring BC emissions from international shipping; investigate appropriate control measures to reduce the impacts of BC emissions from international shipping in the Arctic; and submit a final report to MEPC 65 (in 2014).
The Institute of Marine Engineering, Science and Technology (IMarEST), in association with the International Council on Clean Transportation (ICCT), rose to the challenge and conducted an in-depth review of BC measurement science with the support of international experts in the field, and published its findings, ‘Definition and Measurement of Marine Black Carbon Emissions’, in time for a meeting of the BLG held from 30 January – 3 February 2012. A presentation on the findings provided an overview of the problem, the contribution of BC to climate change; the properties of BC, a proposed definition and other commonly used terms; and updates on measurement methods and impacts.
“We are delighted to play such an active role on a highly topical issue, ” says IMarEST’s Chief Executive, David Loosley. “In addition to the presentation, we were able to submit a paper on the topic to the MEPC. This proposes a definition, identifies potential measurement methods, offers evaluation criteria to compare measurement techniques, and suggests an appropriate measurement method for international shipping, based on expert guidance and scientific review. I would like to commend the members of our Technical Team for their work, which contributes to the current discussions on BC [- both the presentation and paper are on the IMarEST website].
“The definition arrived at by IMarEST and ICCT is that: ‘Black Carbon (BC) is strongly light-absorbing carbonaceous material emitted as solid particulate matter created through incomplete combustion of carbon-based fuels. BC contains more than 80% carbon by mass, a high fraction of which is sp2-bonded carbon, and when emitted forms aggregates of primary spherules between 20 and 50 nm in aerodynamic diameter. BC absorbs solar radiation across all visible wavelengths and freshly emitted BC has a mass absorption efficiency of 5m2/g at the mid-visible wavelength of 550 nm. The strength of this light absorption varies with the composition, shape, size distribution, and mixing state of the particle.’ Undoubtedly defining it, and publicising that definition, will help awareness and understanding globally of the challenge it provides to the maritime industries.
“We look forward to developing more material to aid understanding and to help alleviate the global problems caused by BC.”
Further information on this work is available from technical@imarest.org; the presentation is at www.imarest.org/LinkClick.aspx?fileticket=PunzatczmWw%3d&tabid=216; and the paper at www.imarest.org/LinkClick.aspx?fileticket=DlGGkg122j8%3d&tabid=216.
(Source: IMarEST)
