Cost-Effectiveness of Five Emission Reduction Strategies for Inland River Tugs and Towboats

Waterborne transit is one of the safest and most efficient forms of goods movement. The tug and tow industry transports more than 800 million tons of cargo each year and is a vital component of the U.S. intermodal freight transportation network. However, emissions from tugboat operations on the nation's inland river waterways and at ports affect air quality, public health, and welfare. Although ports and vessel operators can mitigate these environmental impacts with a variety of technological and operational strategies, the effectiveness and cost of each strategy vary greatly. This study analyzes the cost-effectiveness of five tugboat emission reduction strategies: (a) vessel engine repowering, (b) vessel speed reduction, (c) biodiesel, (d) diesel particulate filters, and (e) selective catalytic reduction. Each strategy is evaluated for its emissions benefits, total costs to involved parties (potentially including the tugboat industry, ports, and government agencies), and overall cost-effectiveness in reducing emissions of nitrogen oxide, carbon monoxide, particulate matter, and carbon dioxide. Application to the Ports of St. Louis, Missouri, and Houston, Texas, show that the cost-effectiveness of each strategy varies by port and depends on characteristics of the local tugboat fleet. The results of this study can be applied by public agencies and private operators when considering investments in tugboat emission reduction measures.