Particulate Matter

• Diesel engines on ships produce particulate matter as part of their emissions
• Particulate matter has been shown to be related to health issues in humans
• The harm seems related to the numbers of particles involved, as well as their overall weight.
• There is significant societal from reduction in the particulates from diesel engines (as well as from other sources). (Petrol engines do not create particles in the same way.)
• Particulates are also implicated in climate change. Because they can act as nucleating points, they can modify cloud formation. Because they change the transmission of sunlight through our atmosphere they can alter the light reaching the surface.
• So far, particulate reduction has been pursued as a co-benefit of other technologies

INDEPTH
Until the last decade or so governments tended to regard the emissions from diesel engines as relatively benign, and a small price to pay for the greater efficiency of diesel engines. Few acute effects beyond the unpleasantness of the fumes themselves were recognised.

More recently, science has been able to unpick the longer term and more chronic effects of diesel and particulate emissions, and societies and governments now find that the costs, in shortened lives and poor health, justify more stringent controls on these emissions.

Regulation is no simple matter. The particulates in our ambient air come from many sources, some natural and beyond our control. They are made up of many different materials, not all of which are particularly harmful. They come in many different sizes and it is hard to distinguish the effects of these. Particulates and aerosols are also modified by chemical processes in the atmosphere, and are affected by different conditions, such as sunlight, rain and weather. Indeed, individual particles can be quite exotic in their composition, including solid salts, acids, liquids and soot.

Regulation so far has concentrated on particulate emissions from land transport, and has encouraged integrated approaches, incorporating multiple abatement technologies. These technologies have tended also to constrain the fuel specification, requiring, for example, very low sulphur levels, such as <50ppm. It is not yet clear which approach is likely to be most effective for regulating particulates from shipping