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DECARBONIZATION OF THE INLANDWATERWAY SECTOR IN THE UNITED STATESA REPORT FOR ABS PREPARED BY VANDERBILT UNIVERSITYSEPTEMBER 2021 iofoto/Shutterstock

DECARBONIZATION OF THE INLAND WATERWAY SECTOR IN THEUNITED STATES – PATHWAYS AND CHALLENGES TO A ZERO-CARBONFREIGHT FUTUREPREPARED FOR ABS BY:Dr. Leah A. Dundon, Vanderbilt UniversityDr. Craig E. Philip, Vanderbilt UniversityMadeline C. Allen, Vanderbilt UniversityDavid G. Sehrt, Former Chief Engineering Officer, Ingram Barge CompanyACKNOWLEDGEMENTSThe authors would like to acknowledge the involvement and contribution of Sandor Toth and Criton Corporation,Corning Townsend and C.T. Marine – Naval Architects and Marine Engineers, and Ingram Barge Company. JPDworld/Shutterstock

TABLE OF CONTENTSEXECUTIVE SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Key Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2THE U.S. INLAND RIVER NAVIGATION SYSTEM: BACKGROUND ANDHISTORICAL PERSPECTIVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Historical Developments Leading to a Standardized System of Channels, Locks,Barges and Towboats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Barge Standardization: Key to the System’s Success. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Evolution of the Towboat Fleet: Optimizing Operations on the Inland System . . . . . . . . . . . . . . . . . . 5HISTORY OF U.S. EMISSIONS POLICIES AND THEIR IMPACT ON THEINLAND RIVER FREIGHT SECTOR. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Adoption of the Federal Clean Air Act to Address Air Pollution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Regulation of Pollution from Mobile Sources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Non-road Diesel Engines and the 1990 Clean Air Act Amendments . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Trucks, Trains and Marine Engines –Pollution Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Greenhouse Gas Regulations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10U.S. INLAND WATERWAY FREIGHT MARKET OVERVIEW. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11The 21st Century Mississippi River Markets: A Period of Stability and Resilience . . . . . . . . . . . . . . . 11Decadal Highlights: 2000 to 2010. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Decadal Highlights: 2010 to 2019. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Outlook: 2019 to 2025. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Summary of the Market Assessment and Implications for Towboat Fleet Needs . . . . . . . . . . . . . . . 14CURRENT GREENHOUSE GAS EMISSIONS PROFILE OF THE INLAND FREIGHT SECTOR. . . . . . . 16Towboat Fleet Profile. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Estimate of Annual Fuel Consumption, CO2 Emissions and Carbon Intensity . . . . . . . . . . . . . . . . . . 18DECARBONIZATION POLICY AND TRAJECTORY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20International Agreements and Accords. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20U.S. Federal, State and Regional Initiatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21PATHWAYS TO DECARBONIZATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22Challenges to Decarbonization Specific to the Inland Waterway Sector. . . . . . . . . . . . . . . . . . . . . . . 22Alternative Fuels and Propulsion Systems for the Inland Waterway Fleet –Feasibility Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Biofuel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Liquefied Natural Gas (LNG). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Methanol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26Ammonia. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26Hydrogen. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27Battery Electric Propulsion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27Portable Energy Modules. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29Future Outlook: Market and Regulatory Incentives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31APPENDIX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

TABLE OF FIGURESFigure 1.Figure 2.Figure 3.Figure 4.Figure 5.Figure 6.Figure 7.Figure 8.Figure 9.Figure 10.Figure 11.Figure 12.Figure 13.Figure 14.Figure 15.Figure 16.Figure 17.Figure 18.Figure 19.Figure 20.Figure 21.Figure 22.Figure 23.Evolution of the U.S. Inland Navigation System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Picture of Early Sternwheel Towboat in the Nashville Harbor. . . . . . . . . . . . . . . . . . . . . . . . . . 5Map of the Inland Waterway Operating Territories. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5High Horsepower Towboat Pushing 42 Jumbo Barges. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Age Profile for Inland Waterway Vessels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Historical and Projected Tonnage for Key River-served Markets. . . . . . . . . . . . . . . . . . . . . . 11Historical Cargo Tonnage Comparison: 2002 and 2010. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Historical Cargo Tonnage Comparison: 2010 and 2019. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Historical Energy Cargo Tonnage Comparison: 2010 and 2019. . . . . . . . . . . . . . . . . . . . . . . . 14Historical Coal Tonnage from 2010 to 2019. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Projected Market Outlook to 2025 for Total Ton Movement asCompared to 2019 Observed Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Projected Energy Market Outlook for 2025 as Compared to 2019Observed Energy Market Tonnage Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Average Age of Trans-ocean Commercial Vessels as Compared toAverage Age of Inland Waterway Fleet. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Industry Fleet Profile: Number of Vessels Per Horsepower Category. . . . . . . . . . . . . . . . . . 17GHG Emissions Modal Comparison. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Fuel Intensity by Transportation Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19GHG intensity by Transportation Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19Naval Architect’s Rendering of Internal Mechanics of an Inland River Tugboat. . . . . . . . . 22Naval Architect’s Rendering of Tugboat Tank Plan. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Examples of Four Classes of Towboats and Their Tows. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24Mock Photo of LNG Retrofit Application on Inland Towboat. . . . . . . . . . . . . . . . . . . . . . . . . . 26Smaller “Fleet Boats” (Circled in Red) Assembling Barges for a Tow. . . . . . . . . . . . . . . . . . 27Side View Rendering of a PEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30APPENDIXFigure A-1 Smaller “Fleet Boats” Assembling Barges for a Tow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33Figure A-2 Conventional Diesel Fuel Boat — Hold and Machinery Arrangement.68’ x 34’ x 10’ Twin Screw Z-Drive Towboat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34Figure A-3 Conventional Diesel Fuel Boat — Main Deck General Arrangement.68’ x 34’ x 10’ Twin Screw Z-Drive Towboat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34Figure A-4 Converted Electric Boat — Hold Plan. 1220 BHP Zero-Emission Towboat . . . . . . . . . . . . . . 35Figure A-5 Converted Electric Boat — Outboard Profile. 1220 BHP Zero-Emission Towboat. . . . . . . . 35Figure A-6 Side by Side Comparison of Fully Electric, Zero-emission FleetBoat and Conventional Diesel Fleet Foat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35LIST OF TABLESTable 1.Table 2.Table 3.Table 4.Table 5.Table 6.Marine Diesel Engine Emission Standards-Engine Category Descriptions. . . . . . . . . . . . . .Decadal Summary of Inland Market Demand. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Approximate Annual Fuel Consumption Ranges Per Vessel Horsepower Category. . . . .Energy Density of Alternative Fuels as % of Marine Diesel Fuel. . . . . . . . . . . . . . . . . . . . . . .Inland Towboat Fleet: Key Operational Dimensions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Annual Estimated Potential Carbon Emission Reduction and Fuel Savingsfrom Conversion of Fleet Boats to Electric Propulsion Systems. . . . . . . . . . . . . . . . . . . . . . . 91217232428

DECARBONIZATION OF THE INLAND WATERWAY SECTOR IN THE UNITED STATESEXECUTIVE SUMMARYOcean shipping, along with many other economic sectors, has been focused for several years on decarbonization,consistent with the United Nations Sustainable Development Goal 13 (taking urgent action to combat climatechange) and the United Nations Framework Convention on Climate Change (UNFCCC). The International MaritimeOrganization (IMO) and numerous ocean carriers and shippers have, for some years, been evaluating and workingtowards aggressive goals and strategies to dramatically reduce greenhouse gas (GHG) emissions in internationalshipping. In support of these efforts, ABS has issued comprehensive reports on different pathways to lower (andultimately eliminate) GHG emissions in ocean shipping.Market pressures and international policy and regulations are largely driving the decarbonization initiatives in theinternational shipping sector; however, those drivers are only recently beginning to emerge for domestic shipping,especially with respect to freight shipping on inland waterways in North America (and the U.S. in particular).Examination of pathways toward decarbonization of the inland waterway sector is in its infancy. This report aims toinform key stakeholders by identifying challenges and opportunities that will be faced in moving toward a carbonneutral and zero-carbon future on the inland waterways. The report also includes prospects for furthering thesustainability advantages that barge transport has relative to other surface transportation modes.To develop this report, ABS and Vanderbilt University, through the Vanderbilt Climate Change Initiative (“VCCI”) andthe Vanderbilt Center for Transportation and Operational Resiliency (“VECTOR”), formed an expert working group tobuild a baseline assessment against which future zero-carbon pathways can be evaluated. The working group thatcontributed to this report consisted of researchers with substantial experience in transportation infrastructure andresilience, data analysis and climate change, as well as professionals with extensive industry experience within theinland waterway sector.This report establishes a supportable estimate of the current GHG emissions profile for the inland waterway fleet.The report also evaluates the potential for currently available and possible future propulsion technologies andalternative fuels that may reduce carbon emissions on the inland waterways, and sets forth existing policy challenges,infrastructure needs and competitive market realities and trajectories that present opportunities for and challengesto decarbonization. In particular, the report demonstrates the feasibility of near-term electrification of smaller vesselsoperating on the inland river system through a case study and renderings of a weighted and balanced electrified boatin a retrofit application. As battery technologies continue to improve, this approach has potential application in eventhe largest operating towboats. David Byron Keener/ShutterstockPage 1

DECARBONIZATION OF THE INLAND WATERWAY SECTOR IN THE UNITED STATESKEY CONCLUSIONS The current GHG emissions profile of the inland waterway sector is low compared to other freight modes. The inland waterway sector faces unique challenges that differ from the coastal and trans-ocean shipping sector.These include limits on the vessel length (and overall dimensions), weight and draft. These physical attributes ofthe towboat are constrained in most locations by river depth, width and the size of navigable lock chambers. Electrifying certain inland river boats (smaller boats known as “fleet boats”) can be technically accomplished inthe near-term, through retrofitting of existing boats. Converting all fleet boats to electric propulsion is estimatedto reduce total annual industry fuel consumption by approximately 20 percent, resulting in a similar reduction intotal industry GHG emissions depending on the mix of fuel used to generate the electricity. Electrifying larger river boats may not be feasible with current technology due to the size of batteries required butcould potentially become achievable as battery technologies continue to evolve. Biofuels and methanol are feasible, non-fossil fuel alternatives because they can be used in some existing marineengines and are supported by current infrastructure. Ammonia, hydrogen and liquefied natural gas (LNG) may not be possible as retrofit applications for use inexisting towboats because the comparative energy density of these fuels is substantially lower than that of marinediesel, resulting in the need for larger fuel tank volumes that cannot be accommodated on existing boats. Existingfuel tanks are also not the specialized tanks required for ammonia, hydrogen or LNG. One possible approachto overcome this challenge and successfully use these fuels is to include an alternative fuel barge known as aPortable Energy Module (PEM) within the tow that would generate power on the barge and supply it, in the formof electricity, to the towboat. This approach is technically feasible now but faces economic challenges that willneed market or regulatory incentives to develop. The market for inland waterways is likely to remain stable, so market shifts or growth alone are not likely tojustify new alternative fuel vessels. The inland river mode based on its low emissions profile can be leveraged to attract some shippers, but there isnot likely to be a significant market improvement based solely on the demand for low-carbon inland waterwayshipping. Decarbonizing the inland waterway sector will likely require new regulatory or market-based incentives,similar to those emerging in other economic sectors around the globe, in order to make decarbonizationeconomically viable. Alexander Kuguchin/ShutterstockPage 2

DECARBONIZATION OF THE INLAND WATERWAY SECTOR IN THE UNITED STATESTHE U.S. INLAND RIVER NAVIGATION SYSTEM: BACKGROUND ANDHISTORICAL PERSPECTIVESOver the last 10 years, there has been a growing focus on decarbonization in the transportation sector, including inthe international shipping arena. With the exception of some attention from the European Union, there has beenlittle focus on decarbonization pathways in the shallow draft inland navigation sector. While inland river navigationshares some similarities with trans-ocean shipping, there are important challenges and opportunities unique to theinland sector that are primarily attributable to the development of the physical infrastructure in each geographicalriver area and the outlook for the markets served. To help understand the opportunities and constraints applicableto inland river decarbonization trajectories, a brief historical overview is provided in this section, with a historicalmarket review and projected market outlook in the U.S. Inland Waterway Freight Market Overview section. The driversof tonnage demand are critical considerations to achieving a low- or zero-carbon future on the inland rivers.HISTORICAL DEVELOPMENTS LEADING TO A STANDARDIZED SYSTEM OF CHANNELS,LOCKS, BARGES AND TOWBOATSCommercial use of the nation’s inland waterways originated with the country’s founding—beginning with rivers alongthe eastern seaboard and continuing with the construction of elaborate canal systems that extended these waterways.Construction included the Erie Canal in New York, and quickly extended to the westward frontier down the Ohio Riverand beyond to the Mississippi River. Flat-bottom boats allowed one-way travel all the way to New Orleans, and roundtrip travel emerged with the arrival of steamboats in the 19th century.1The Federal Government, through the U.S. Army Corps of Engineers (Corps), became responsible for establishing theinfrastructure to allow commercial navigation on designated waterways such as the Ohio and Mississippi Rivers. TheCorps’ work in the early 20th century began with a series of 53 “wicket” dams constructed along the Ohio River, withlocks to allow passage during low water when the wickets were raised. The first projects achieved a channel depth ofsix feet, but Congress legislated a nine-foot channel in the Rivers and Harbors Act of 1910, which became the minimumchannel depth adopted on the Ohio River and applied to new projects on the inland river network. This nine-footdesign standard survives to this day.The construction of a modern system of navigational dams along the Mississippi River began during the GreatDepression, and by the start of World War II (WWII), a total of 27 lock and dam projects were constructed between St.Louis and the Twin Cities (Minneapolis and St. Paul, Minnesota). Lock and dam projects followed on the Illinois River,allowing connection to the Great Lakes at Chicago and on the Tennessee and Cumberland Rivers, which coincidedwith the creation of the Tennessee Valley Authority in the 1930s.In the post-WWII era, a comprehensive modernization program commenced on the Ohio River, and the 53 wicketdams were replaced by 20 fixed dams with navigation locks, which were finally completed in the 1970s. This upriversystem extended north from New Orleans and reached Pittsburgh, Chicago and Minneapolis. This system also wasconnected to a shallow draft navigable channel established along the Gulf Coast from Brownsville, Texas, to the FloridaPanhandle, called the Gulf Intracoastal Waterway. The timing and the network’s extent are shown in Figure 1.Editorial use only. Joseph Sohm/Shutterstock1The History of Large Federal Dams: Planning, Design, and Construction in the Era of Big Dams. U.S. Department of the Interior (2005).Page 3

DECARBONIZATION OF THE INLAND WATERWAY SECTOR IN THE UNITED STATES Ingram Barge CompanyFigure 1. Evolution of the U.S. Inland Navigation SystemBARGE STANDARDIZATION: KEY TO THE SYSTEM’S SUCCESSAs noted previously, a nine-foot channel was guaranteed through a statutory mandate enacted more than 100years ago along this network of more than 12,000 interconnected miles. A uniform lock chamber size was notmandated by law, but the earliest locks built along the Ohio River were built with a width of 110 feet and lengthof 600 feet, and this became the standard minimum size as new locks were constructed on various segments.In many cases, longer locks up to 1,200 feet in length were constructed where conditions permitted, and whereanticipated traffic volumes justified the expense, but lock width has never varied.Commercial users of these waterways converged on standardized sizes for the barges that would best utilize thesystem. Limited by the size of the lock, two barge sizes emerged. The most common was 195 feet by 35 feet, oftencalled “Jumbo” barges. The second, larger barge size was 295 feet by 54 feet, often called “Oversize” barges. A groupof nine Jumbo barges or four Oversize barges, assembled as a unit, could fit into the lock chamber, and variousoperational strategies emerged that allowed tows (an assembly of barges tied together) of up to 15 Jumbo barges oreight Oversized barges to be moved by a single towboat on most locking rivers.The amount of freeboard, or height from waterline to deck level, that was considered necessary for safe vesseloperations was two to three feet when the vessel was fully loaded. Because the system was guaranteed to maintaina nine-foot channel everywhere, barges were built with 12-foot hulls so that when loaded to a nine-foot draftthey would maintain two feet to three feet of freeboard. In recent years, some operators have built deeper bargeswith up to 14-foot hulls, recognizing that channels in some locations and during some parts of the year are oftendeeper than the nine-foot minimum guaranteed by statute and maintained by the Corps. When allowed, thesedeeper barges can carry up to 20 percent more cargo.Page 4

DECARBONIZATION OF THE INLAND WATERWAY SECTOR IN THE UNITED STATESEVOLUTION OF THE TOWBOAT FLEET: OPTIMIZING OPERATIONS ON THE INLAND SYSTEMUntil the 1930s, barges were pushed by steam-powered sternwheelers, the largest of which generated less than 1,000horsepower (hp). See Figure 2. Ingram Barge CompanyFigure 2. Picture of early sternwheel towboat in the Nashville Harbor.During the 1940s and 1950s, diesel-powered towboats displaced the steam-powered vessels, much as diesel electriclocomotives replaced steam engines on the nation’s railroads. Much larger twin and triple screw vessels were possible,and the deployment of flanking rudders allowed them to maneuver much larger tows despite the narrow channelsfound in many locations.Because most of the locks on the river system could accommodate tows of 15 Jumbo barges or eight Oversized barges,operators determined that the towboats best deployed along the locking rivers consisted of 4,000 to 6,000 hp boats.Along the Gulf Intracoastal Waterway, a narrow channel, smaller towboats of approximately 2,000 hp are employed.Figure 3 shows the operating territories highlighted with associated tows (the barge assembly) assigned to achieve thelowest possible unit towing cost. Ingram Barge CompanyFigure 3. Map of the inland waterway operating territories.The Mississippi River between St. Louis and New Orleans was navigable without the locks and dams which limited towsizes. Operators learned that the maximum safe tow size was about 40 Jumbo barges and required a towboat of 9,000 to10,500 hp. These impressive units, as pictured in Figure 4, have a footprint larger than a U.S. aircraft carrier and push asmuch cargo as the largest ships that transit the Panama Canal.Page 5

DECARBONIZATION OF THE INLAND WATERWAY SECTOR IN THE UNITED STATES Ingram Barge CompanyFigure 4. High horsepower towboat pushing 42 Jumbo barges.Assembling groups of barges together – often with different barges serving different customers – permitted operatorsto achieve the maximum efficiency possible during the linehaul (river) portion of the voyage. However, this assemblyprocess required the establishment of a network of hundreds of docks as well as fleets to load and stage the barges.Each dock and fleet required one or more smaller towboats (800-1,400 hp), often referred to as “fleet boats,” that weresmaller and could efficiently assemble the barges.As shown in Figure 5 below, most towboats that are in service today were built during the 20-year period from 1970to 1990, both to replace older, smaller equipment constructed prior to the completion of the waterway network, and toaccount for the rapid growth in tonnage that took place beginning in the 1970s. Unlike barges, the towboat effectivelyhas an indefinite useful life if properly maintained. The sections below discuss in more detail towboat longevity as afactor in the development of decarbonization strategies.Despite their age, the size and hull configurations have not changed materially since the 1960s, and operation infreshwater limits hull wastage (corrosion). Operators have thus been incentivized to repower and upgrade propulsionand other systems over the years rather than retire older vessels outright. This of course has significant implicationswith respect to conversion to new lower carbon propulsion systems.Figure 5. Age profile for inland waterway vessels. Source: Inland River Record.Page 6

DECARBONIZATION OF THE INLAND WATERWAY SECTOR IN THE UNITED STATESHISTORY OF U.S. EMISSIONS POLICIES AND THEIR IMPACT ON THE INLANDRIVER FREIGHT SECTORIn 2007, the Supreme Court’s decision in Massachusetts v. EPA, holding that the federal Clean Air Act (CAA) authorizedthe U.S. Environmental Protection Agency (“EPA”) to regulate greenhouse gases (GHG), ushered in a series of agencyrulemakings aimed directly at reducing GHG emissions from mobile sources (both road and non-road). Prior tothose rulemakings, GHG emissions were not regulated by EPA; however, a number of laws and regulations directedat reducing other air pollutants or increasing efficiency in certain mobile sour

David G. Sehrt, Former Chief Engineering Officer, Ingram Barge Company ACKNOWLEDGEMENTS The authors would like to acknowledge the involvement and contribution of Sandor Toth and Criton Corporation, . Naval Architect’s Rendering of Internal Mechanics of an Inland River Tugboat . . . . . . . . . 22 Figure 19 . Naval