Emissions from Waterborne Commerce Vessels in United States Continental and Inland Waterways

We present an inventory of emissions from marine vessels engaged in waterborne commerce (i.e., cargo transport) on the U.S. navigable waters. Emissions are estimated for 1997 for various U.S regions and types of traffic, including oceangoing (international), coastwise (domestic), inland-river system, and Great Lakes. Nearly all emissions in U.S. waters occur in shipping channels outside of port regions, either on rivers or within 200 miles of shore. NOx emissions from commercial marine engines considered in this study account for about half of the U.S. EPA baseline inventory of ∼1000 tons per year for all marine vessels ((1)). This equals 4% of all U.S. transportation emissions, more than double previous nationwide inventories of vessel emissions ((2)). Waterborne commerce emissions are not negligible when compared to other sources. In fact, in many regions NOx emissions from waterborne commerce rank higher than other source categories, which are regulated at the state and federal levels. NOx emissions from river commerce in the top 20 states with waterborne trade account for 65% of total waterborne commerce emissions in those states. In contrast, 72% of SOx emissions in these states occurs along coastal (Ocean or Great Lake) areas, where high-sulfur fuels are more commonly used.