Navigating Atmospheric Emissions from Shipping in the Great Lakes Basin

The Great Lakes shipping network constitutes a critical corridor for North America, transporting bulk commodities– including iron ore, coal, stone, grain, and aggregates– while linking regional industrial hubs to international markets via the St. Lawrence Seaway. This inland navigation system underpins regional economic activity and serves as a strategic interface between freshwater and ocean-going trade. Historically, many bulk carriers, particularly older lakers, relied on high-sulfur residual fuel oil, producing substantial emissions of sulfur oxides, nitrogen oxides, particulate matter, and carbon dioxide. These emissions contribute to pollution, pose significant public health risks, and affect sensitive aquatic and terrestrial ecosystems across the Great Lakes Basin.

To mitigate these impacts, vessels operating within the North American Emission Control Area are mandated to comply with stringent fuel sulfur limits and engine emission standards. Fuel sulfur content is capped at 0.1% by mass for diesel engines in designated waters, while nitrogen oxides and particulate matter emissions are regulated according to engine tier standards established under the MARPOL 1973/78 protocol (Annex VI) and enforced domestically through the U.S. Act to Prevent Pollution from Ships. Compliance is monitored via fuel verification, vessel inspections, and operational audits conducted by the EPA and USCG. Vessels typically meet these requirements through one of two primary strategies:

Residual Fuel Oil with Exhaust-Gas Scrubbers

Many legacy Great Lakes bulk carriers continue to operate on high-sulfur residual fuel oil but achieve regulatory compliance through the use of exhaust-gas scrubbers. These systems remove sulfur dioxide from exhaust by passing gases through an alkaline solution, commonly sodium hydroxide, which neutralizes sulfur oxides, producing an inert byproduct. Scrubbers enable vessels to maintain the economic advantages or residual fuel while simultaneously controlling sulfur and particulate emissions.

The Interlake Steamship Company utilizes this strategy, retrofitting multiple vessels with closed-loop scrubbers to reduce stack emissions without altering engine design. While scrubber installation entails significant upfront capital investment and ongoing operational maintenance, it leverages existing fuel infrastructure and allows older, high-capacity vessels to remain economically viable under contemporary emission standards.

Ultra-Low Sulfur Diesel and Biofuels

An alternative compliance pathway involves the substitution of traditional heavy fuel with ultra-low sulfur diesel or renewable biofuels. These fuels inherently satisfy sulfur limits, removing the need for exhaust-gas treatment. Biofuels, such as B50 or B100 blends, also provide additional reductions in lifecycle greenhouse gas emissions relative to conventional fossil fuels.

Canada Steamship Lines has implemented this approach on the Great Lakes, operating several vessels on biodiesel blends during navigation seasons. This “drop-in” fuel strategy allows immediate compliance with emission standards without engine modifications, offering substantial environmental benefits. However, it generally incurs higher fuel costs and depends on reliable access to biofuel supply infrastructure.

These two strategies– scrubbers with residual fuel and alternative fuels– currently dominate the Great Lakes fleet. Scrubber retrofits offer cost-effective compliance for older, high-capacity vessels, whereas low-sulfur diesel and biofuels enable rapid decarbonization without extensive technological investment.

Decisions regarding fuel and emission-control strategies on the Great Lakes have implications beyond pollution output. Bulk commodities transported through this system feed global supply chains via the St. Lawrence Seaway, meaning emission reductions achieved inland contribute to the environmental sustainability of international maritime trade. By reducing sulfur and greenhouse gas emissions, operators of the Great Lakes not only protect regional ecosystems and public health but also advance broader global efforts to mitigate climate change and marine pollution.