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Vanderbilt study examines decarbonization of US inland waterways

A "landmark" new report by transportation and environmental engineers at Vanderbilt University on behalf of the American Bureau of Shipping (ABS) looks toward the decarbonization of American inland waterways and the potential for possible future propulsion technologies and alternative fuels to reduce carbon emissions.

A “landmark” new report by transportation and environmental engineers at Vanderbilt University on behalf of the American Bureau of Shipping (ABS) looks toward the decarbonization of American inland waterways and the potential for possible future propulsion technologies and alternative fuels to reduce carbon emissions (photo courtesy VCCI).

In 2018, the UN International Maritime Organization (IMO) set a goal to cut the maritime shipping industry’s greenhouse gas (GHG) emissions by at least half by 2050. The comprehensive “Decarbonization of the Inland Waterway Sector in the United States” study, is the first to examine the US inland waterway system through the lens of reducing greenhouse gas (GHG) emissions.

The study was conducted by Vanderbilt University on behalf of the American Bureau of Shipping (ABS), a leading global provider of classification and technical advisory services to the marine and offshore industries. The research itself is a collaboration between the Vanderbilt Center for Transportation and Operational Resiliency and the Vanderbilt Climate Change Initiative (VCCI).

While the greenhouse gas profile of the inland waterways is low compared to other shipping sectors, the need to decarbonize operations is growing more pressing all the time. The sector faces unique challenges and limitations and will require a bespoke emissions approach, which is analyzed in this study with Vanderbilt University. Electrification clearly offers smaller inland river vessels swift gains in CO2 reduction, but the report also explores the wider decarbonization landscape that will need to be navigated to put this sector on a sustainable footing, said Georgios Plevrakis, Director Global Sustainability at ABS.

The inland waterway sector faces unique challenges to decarbonization that coastal and trans-ocean shipping does not. River depth and width, plus the lock system and lock sizes, limit vessel length and overall dimensions, weight, and draft. The maximum underwater depth for a tug and barge, for example, is 10 feet (just over 3 m).

There has been a lot of work focused on decarbonizing the international and coastal shipping sector but much less focus on the inland river sector, in part because it is already one of the most sustainable ways to move freight. The inland river sector has some unique technical characteristics that present real challenges to successful decarbonization, but we are excited about some of the possibilities and pathways we identified in this report, said Dr Leah Dundon, Director Vanderbilt Climate Change Initiative (VCCI).

Electrification option for fleet boats

The research team found that electrifying larger riverboats may not be feasible with current technology because of the large batteries required.  However, retrofitting certain smaller boats known as “fleet boats” could be accomplished in the near term.

Converting all fleet boats to electric propulsion is estimated to reduce total annual average industry diesel fuel consumption by approximately 20 percent, depending on the fuel types used to generate electricity. Each of the 1 000 fleet boats uses about 100 000 (US) gallons (≈ 378 500 litres) of marine diesel annually.

The report includes a case study and naval architect renderings of a retrofitted, weighted, and balanced electrified boat.

Drop-in biofuels could replace marine diesel

Outside of electrification, the potential for using alternative fuels is mixed. Biofuels, such as marine biodiesel and renewable diesel, and (bio)methanol present the most feasible options because they can be used in some existing marine engines and are supported by the current infrastructure, the report finds.

Biodiesel and renewable diesel fuels also have energy density near to that of marine diesel, meaning existing onboard fuel tank size may be sufficient.

Other alternative fuel options such as ammonia, hydrogen, and liquefied natural gas (LNG)—which as fossil-derived fuels have lower emissions than marine diesel—have substantially lower comparative energy density than marine diesel, which would require significantly larger tank volumes. Existing onboard tanks cannot be used.

The study includes analyses of historic and projected cargo tonnage, the feasibility of alternative fuel options, and current market conditions. The authors note that decarbonization of the inland waterway sector likely will require regulatory or market-based incentives.

We are excited about some of the possibilities and pathways identified in this report. For example, we are hopeful that a pilot project based on river fleet boat electrification can be accomplished in the near term, which would inform scalability potential and cost, as well as further research needs. These types of grand challenges can’t be undertaken alone—they require input and insight from a broad range of skill sets and expertise, so Vanderbilt was extremely pleased to collaborate with ABS on this project, Dr Dundon said.

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