Personal watercraft (PWC), are high polluters relative to their engine size and usage
Small engines, such as conventional two stroke engines used in marine outboard and personal watercraft (PWC), are high polluters relative to their engine size and usage. These small engines emit volatile organic compounds (VOCs) and oxides of nitrogen (NOx) which contribute to ozone (photochemical smog) formation in summer. They also emit particles, carbon monoxide (CO) and a range of water and air toxics such as benzene.
The United States, California and Europe regulate exhaust emissions from marine engines – the USA has had these in place since 1998. Canada, which has an interim Memorandum of Understanding with the industry, is preparing to introduce outboard emissions regulations. There are no Australian regulations or standards that limit air and water emissions from marine outboard engines. However, as all marine engines sold in Australia are imported, many do comply with emission standards applicable to the country of origin or other regulated markets. On the other hand overseas manufacturers produce high emissions marine outboard engines to sell in unregulated markets such as Australia.
As substantial power is required to move small boats through water even the better performing small engines that comply with overseas emission limits emit far greater quantities of pollutants per hour than typical modern car engines. For example one hour of operation of a boat that complies with US 2006 emission standards (i.e. has a relatively clean engine) produces the same pollution as about fifty cars operated at a similar speed. Older style outboard engines that do not comply with US EPA 2006 limits are likely to emit around ten times the amount of pollution compared to conforming engines.
Estimates from the National Pollutant Inventory suggest that marine outboard engines contribute approximately 2.5 percent of the VOCs emitted into Australian urban airsheds from anthropogenic sources. Recently released emissions inventory data from NSW’s Department of Environment and Conservation, indicates that the contribution during summer weekends, periods when conditions are particularly conducive to ozone formation, is around 9 percent.
National Environment Protection (Ambient Air Quality) Measure (Air NEPM) ozone standards are being reviewed and based on current human health evidence the argument appears to be strengthening for tighter ozone standards. Sydney’s Greater Metropolitan Region (GMR) annually records exceedances of the current Air NEPM ozone standards while other jurisdictions meet, or are close to meeting the current ozone standards. Should a stricter standard or an eight-hour standard consistent with international standards/guidelines be adopted, achievability of Air NEPM ozone standards or goals could become an issue for some of the other major urban airsheds and additional strategies to reduce precursor emissions from as yet uncontrolled sources such as outboard engines may be required.
