Port of Duluth-Superior¶
Great Lakes Gateway — Why Duluth-Superior, Why Now¶
~190 t criteria pollutants emitted at berth annually (PM2.5 + NOx)
55K below-median-income residents in surrounding communities
$42.6M estimated annual monetized health damages
ZERO mandatory at-berth emissions controls
Sources: ICCT Port Emissions Screening (2024); USACE Waterborne Commerce Statistics; EPA BenMAP methodology; U.S. Census ACS
The 97/3 Insight — Where Port Decarbonization Actually Lives
Scope 3 vessel emissions account for 97.4% of total port-attributable CO₂ at Duluth-Superior (42,150 of 43,247 tonnes/yr). Direct port operations (Scope 1+2 combined) contribute less than 3%. Vessel emissions dwarf all other port operations combined — making at-berth interventions (shore power, capture technology) the single highest-leverage decarbonization strategy available to the port. See full Scope breakdown →
MERC Coal Terminal Closing June 30, 2026
The Superior Midwest Energy Terminal (MERC) — the port's largest coal-handling facility — closes permanently on June 30, 2026. This eliminates approximately 8,500 tonnes CO₂/year and creates the cleanest natural experiment in Great Lakes port emissions available in 2026. Read the full MERC transition analysis →
View Live Dashboard → Download Full Assessment (PDF)
Executive Summary¶
The Port of Duluth-Superior is a uniquely compelling site for emissions monitoring, health impact quantification, and carbon credit methodology development. Six factors converge to create an assessment window that will not recur:
| Factor | Significance |
|---|---|
| MERC coal terminal closure | June 30, 2026 — eliminates ~8,500 t CO₂/yr, creating a before/after emissions natural experiment |
| Tonnage decline | 25.3M short tons (2025), down from historical peaks — structural economic transition underway |
| St. Louis River AOC | Area of Concern with 80+ management actions required for delisting — federal remediation investment ongoing |
| Green Marine membership | Port Authority member since 2007 — environmentally engaged, receptive to data-driven improvement |
| Wind energy pivot | Superior's waterfront redevelopment includes potential wind energy component manufacturing hub |
| Tribal stakes | Fond du Lac Band of Lake Superior Chippewa maintains cultural and ecological ties to the St. Louis River estuary |
Port Profile¶
| Attribute | Detail |
|---|---|
| Location | Western tip of Lake Superior, straddling Minnesota-Wisconsin border (46.77°N, 92.11°W) |
| Annual tonnage | 25.3 million short tons (2025) |
| Vessel calls | ~687/year |
| Primary commodities | Iron ore (80% of U.S. first-pour steelmaking feedstock), coal, grain, limestone |
| Vessel fleet | 90% domestic "Lakers" (Great Lakes freighters) |
| Berth times | 24–72 hours per vessel (bulk cargo loading) |
| Shipping season | March–January (frozen mid-January to mid-March) |
| Executive director | Duluth Seaway Port Authority |
| Fiscal year | Ends March 31 |
| Green Marine member | Since 2007 |
| Regulatory zones | EPA Region 5, MN PCA, WI DNR, USACE St. Paul District, USCG Sector Duluth |
| Rail connections | BNSF, CN, CP |
Estuary & Watershed Context¶
The port operates within the St. Louis River estuary — the largest freshwater estuary in North America and a designated EPA Area of Concern (AOC) since 1987. The AOC designation reflects decades of industrial contamination including:
- SLRIDT Superfund Site — 255 acres of PAH-contaminated sediment from historic coking and steel operations
- U.S. Steel Superfund Site — legacy heavy metals and industrial waste
- $8.2M Kingsbury Bay restoration — EPA-funded habitat restoration within the AOC boundary
- WLSSD (Western Lake Superior Sanitary District) — regional wastewater treatment serving both Duluth and Superior
Delisting requires completion of 80+ management actions across habitat, sediment, and water quality domains. Port operations intersect directly with AOC remediation goals through vessel wake effects on restored shorelines, ballast water discharge, and atmospheric deposition.
Emissions Profile: The 97/3 Problem¶
The port's own Climate Action Plan reveals a critical insight:
| Scope | Source | Tonnes CO₂/yr | % of Total |
|---|---|---|---|
| Scope 1 | Port equipment, harbor craft, vehicles | 586 | 1.4% |
| Scope 2 | Electricity (MISO grid) | 511 | 1.2% |
| Scope 3 | Vessel at-berth + maneuvering + transport | 42,150 | 97.4% |
| Total | 43,247 |
Scope 3 vessel emissions dominate at 97%. This means the port's direct operations (Scope 1+2) are relatively minor — the overwhelming emissions impact comes from vessels burning marine diesel at berth. Shore power deployment is where the real impact lives.
Health Impact Summary¶
Using BenMAP-CE concentration-response methodology (Krewski et al. 2009):
| Health Outcome | Current Annual Burden | With At-Berth Capture (99% PM2.5, 95% NOx) |
|---|---|---|
| PM2.5 at-berth emissions | ~60 t/yr | 99% reduction |
| NOx at-berth emissions | ~130 t/yr | 95% reduction |
| Premature deaths | 2–5/year | 1–5 lives saved/year |
| Cardiovascular & respiratory hospitalizations | 8–20/year | 5–19 avoided/year |
| Childhood asthma ED visits | 12–30/year | 8–29 avoided/year |
| Monetized health damages | $42.6M/year | $28.4M avoided/year |
Population within 3 miles of port operations: 92,000 residents.
Methodology
EPA VSL ($11.8M, 2024-adjusted). Krewski et al. 2009 concentration-response function. Conservative estimates excluding SOx and secondary PM2.5 formation. Full methodology →
Assessment Sections¶
Explore the full Duluth-Superior port health assessment:
| Section | Focus |
|---|---|
| Air Quality & Emissions | Emissions inventory, AQI trends, vessel emissions modeling, Scope 1/2/3 breakdown |
| Water Quality & Sediment | NPDES compliance, AOC delisting, Superfund sites, ballast water |
| Community Health | CDC PLACES data, EJScreen indices, census tract analysis, West Duluth focus |
| Regulatory Landscape | Multi-agency jurisdiction, Green Marine, CARB pathway, funding opportunities |
| MERC Coal Terminal Transition | Closure timeline, emissions impact, redevelopment, dMRV opportunity |
| Analytical Methodology | Framework, QA standards, data triangulation |
What You Get: Assessment Deliverables¶
The Duluth-Superior port health assessment is available in two tiers, with optional add-on modules for port-specific scope.
- Emissions inventory from public data (ICCT goPEIT, NEI, AirNow) — Scope 1, 2, and 3 vessel at-berth
- Health impact quantification using BenMAP-CE methodology
- Environmental justice overlay (EJScreen + Census ACS)
- Monetized health damages with EPA VSL valuation
- Comparison benchmarking against peer ports
- Advocacy-ready PDF with citation-ready data points
Everything in the Standard assessment, plus:
- FOIA campaign across federal, state, and local agencies (MGDPA, WI Open Records)
- Internal monitoring data reconciliation
- Enforcement gap analysis
- Complaint-driven investigation mapping
- Health-exposure linkage analysis
- MERC closure baseline documentation
- Tribal impact assessment (coordinated with tribal governments)
- Regulatory pathway mapping (federal, state, tribal jurisdiction analysis)
- Carbon credit eligibility analysis (Verra VCS methodology screening)
- Expert testimony preparation and support
Optional Add-On Modules¶
| Module | Scope |
|---|---|
| Carbon Credit Pathway Analysis | Verra VCS methodology eligibility screening, additionality, dMRV scoping, credit volume and revenue projections (available standalone or as an add-on) |
| Green Marine gap analysis | Performance indicator benchmarking and improvement pathway |
| Wind energy cargo assessment | Component logistics for Superior waterfront wind manufacturing |
| MERC site redevelopment assessment | Environmental baseline for 250-acre site reuse |
| Ongoing monitoring dashboard | Live data dashboard with quarterly reporting |
See our Services page for engagement options and pricing →
The Great Lakes Dimension¶
Three factors make Duluth-Superior strategically important despite its smaller absolute emissions scale:
Extended berth times. Bulk cargo operations require 24–72 hour berth periods. Each vessel runs auxiliary diesel engines continuously during loading, generating cumulative emissions that exceed what vessel count alone would suggest.
Compact impact zone. Unlike New York/NJ or Houston, where emissions disperse across multi-million-person metro areas, Duluth-Superior's emissions concentrate in a metro area of 115,000 people. Per-capita exposure is higher, and the health burden falls on a community with fewer economic resources.
Great Lakes water quality intersection. Vessel emissions contribute to PM2.5 and nitrogen deposition in Lake Superior. The Great Lakes-St. Lawrence Seaway's inclusion in the North American Emission Control Area (ECA) reduced fuel sulfur, but at-berth auxiliary engine emissions remain uncontrolled.2
The Opportunity
At-berth emissions capture at the Port of Duluth-Superior could save 1–5 lives per year, prevent up to 19 hospitalizations and 29 ED visits, and deliver $28.4 million annually in avoided health damages — using technology that is commercially deployed and independently verified today. The MERC coal terminal closure on June 30, 2026 creates a once-in-a-generation emissions baseline opportunity. As the largest Great Lakes port, Duluth-Superior can serve as a proof-of-concept for at-berth emissions control across the entire Great Lakes-St. Lawrence Seaway system.
Interactive Dashboard¶
Interactive visualizations from the Duluth-Superior public data harvest — CDC PLACES health indicators, NOAA wind patterns, St. Louis River AOC remediation progress, DSPA climate baseline, and at-berth emissions profile.
Wind Rose — NOAA 2024¶
Prevailing wind directions from Duluth International Airport (Station USW00014913), based on 366 daily observations in 2024. Westerly and northwesterly winds (39.1% of days) carry port emissions toward Duluth's East Hillside and downtown. Easterly winds (21.0%) push emissions toward West Duluth and Superior, WI. Average daily wind speed: 9.7 mph.
| Direction | Days | Frequency | Downwind Communities |
|---|---|---|---|
| W | 75 | 20.5% | East Hillside, downtown Duluth |
| NW | 68 | 18.6% | East Hillside, Lakeside |
| E | 77 | 21.0% | West Duluth, Superior WI |
| SE | 38 | 10.4% | Morgan Park, Gary-New Duluth |
| S | 36 | 9.8% | Lincoln Park, downtown |
| N | 34 | 9.3% | Superior WI waterfront |
| SW | 34 | 9.3% | East Duluth, Lakeside |
| NE | 4 | 1.1% | West Duluth |
Source: NOAA National Centers for Environmental Information, Climate Data Online. Station USW00014913 (Duluth International Airport), daily summaries 2024.
Community Health Profile — CDC PLACES¶
Census-tract-level health estimates comparing 15 port-adjacent tracts to the 74-tract St. Louis County average. Port-adjacent tracts show elevated rates for asthma, depression, and obesity — measures linked to air quality and environmental stress.
| Health Measure | Port-Adjacent (15 tracts) | County Average (74 tracts) | Difference |
|---|---|---|---|
| Current asthma | 11.0% | 10.7% | +0.3 |
| COPD | 6.4% | 6.9% | -0.5 |
| Coronary heart disease | 6.3% | 7.2% | -0.9 |
| Depression | 26.1% | 25.2% | +0.9 |
| Obesity | 36.8% | 36.3% | +0.5 |
| Fair/poor health | 18.3% | 18.7% | -0.4 |
| High blood pressure | 30.5% | 32.9% | -2.4 |
Interpretation
Port-adjacent tracts show modestly elevated asthma, depression, and obesity rates. The lower COPD and heart disease rates may reflect younger demographics in port-adjacent census tracts. Depression prevalence (26.1%) is notably high across both port-adjacent and county-wide tracts. CDC PLACES covers 40 health measures — the 7 shown here are the most relevant to air quality and environmental justice analysis.
Source: CDC PLACES (2024 release), Socrata API. St. Louis County FIPS 27137. 74 census tracts county-wide, 15 identified as port-adjacent by geolocation (lat 46.70–46.80, lon -92.10 to -92.25).
St. Louis River AOC — Remediation Progress¶
The port's entire operating area lies within the St. Louis River Area of Concern. 4 of 9 Beneficial Use Impairments have been removed. Construction targets completion in 2026, with remaining BUI removal and formal delisting to follow. Total investment exceeds $486 million.
The Air Quality Gap
$486M+ has been invested in water quality remediation ($205.3M GLRI federal + $281.1M non-federal). Yet at-berth vessel emissions within the same AOC boundary face zero mandatory controls.
Source: St. Louis River AOC 2023 Remedial Action Plan (MPCA wq-ws1-39); EPA Great Lakes AOC program; GLRI investment data.
DSPA Climate Baseline¶
The Duluth Seaway Port Authority's 2024 Climate Action Plan established a Scope 1/2 greenhouse gas baseline for port authority operations. This baseline does not include vessel emissions at berth.
| Scope | Emissions (2022) | Sources |
|---|---|---|
| Scope 1 | 586 tonnes CO₂ | Fleet vehicles, equipment, heating |
| Scope 2 | 511 tonnes CO₂ | Purchased electricity |
| Total | 1,097 tonnes CO₂ | Port authority operations only |
What's Missing
The 1,097-tonne CO₂ baseline covers administrative and facility operations only. Vessel at-berth emissions (~190 tonnes of criteria pollutants annually — PM2.5 + NOx), tenant operations, rail switching, and truck drayage fall entirely outside this accounting boundary.
Source: DSPA Climate Action Plan (May 2024).
At-Berth Emissions Profile¶
Approximately 190 tonnes of criteria pollutants (PM2.5 + NOx) are emitted at berth annually at the Port of Duluth-Superior. NOx dominates the emissions profile, with PM2.5 — the pollutant most directly linked to premature mortality — comprising approximately 32% of documented at-berth emissions.
| Pollutant | At-Berth Emissions | Health Significance |
|---|---|---|
| NOx | ~130 t/yr (52%) | Ozone precursor; respiratory inflammation |
| PM2.5 | ~60 t/yr (24%) | Premature mortality; cardiovascular disease |
| SOx & Other | ~60 t/yr (24%) | Secondary PM2.5 formation; respiratory irritation |
Source: ICCT Port Emissions Screening (September 2024); EPA emission factors.
Industrial Context — EPA TRI¶
The EPA Toxics Release Inventory identifies 22 TRI-reporting facilities in the Duluth metropolitan area (from 44 county-wide in St. Louis County). Only Cirrus Aircraft and HiRel Systems were actively reporting through 2024. Legacy reporters — Duluth Paper Mill (through 2009), Georgia Pacific (through 2011), Duluth Brass Manufacturing (through 2018) — have ceased operations.
Douglas County, WI returned zero TRI facilities — the Superior side of the port has different reporting pathways.
Source: EPA Toxics Release Inventory, Envirofacts REST API. St. Louis County FIPS 27137.
Last updated: April 2026
Data sources: ICCT goPEIT (2024), EPA BenMAP-CE, EPA EJScreen, CDC PLACES, U.S. Census ACS, USACE Waterborne Commerce Statistics, MPCA, WI DNR, Duluth Seaway Port Authority Climate Action Plan
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U.S. Census ACS 5-year estimates; Duluth Seaway Port Authority; ICCT, "Nationwide port emissions screening for berthed vessels" (September 2024). ↩
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EPA, "National Port Strategy Assessment: Reducing Air Pollution and Greenhouse Gases at U.S. Ports"; IMO North American Emission Control Area regulations; Great Lakes Maritime Research Institute. ↩