88 Proceedings Fall 2025 Understanding Coal by LT Eva McNell Staff Engineer Hazardous Materials Division U.S. Coast Guard Office of Design & Engineering Standards CHEMICAL O F T H E Q UA R T E R What is it? Coal, a highly combustible material, is a sedimentary rock primarily composed of amorphous carbon and hydrocar- bons which, due to its energy density and relatively low cost as fuel, is the largest source of electricity generation in the world. It falls under the classification of “materials haz- ardous only in bulk” in both its bituminous and anthra- cite forms. It is regulated in maritime transportation by the U.S. Coast Guard, the Department of Transportation, and the International Maritime Organization (IMO). Why should I care? Energy Production About half of the United States coal—the nation’s most abundant fossil fuel—is bituminous. Bituminous coal varieties consist of smithing, cannel, and coking coal. The steel industry relies heavily on coking in produc- tion efforts due to its low moisture content and stability. Globally, China is the leading producer of coal, followed by India, Indonesia, and the United States respectively. Environmental & Human Health Impacts When burned, the carbon contained in coal reacts with oxygen to form carbon dioxide, or CO2. Coal can contain varying amounts of sulfur, which oxidizes to form sul- fur dioxide, or SO2 which can form sulfuric acid when it reacts with water. Similarly, nitrogen compounds in coal are oxidized to form nitrogen oxides, or NOx. Fine par- ticulate matter formed during coal combustion penetrates the lungs and contributes to respiratory, cardiac, and can- cer mortality. While coal is almost phased out as a source of maritime fuel, SO2 and NOx emissions are of interna- tional environmental concern and regulated by the IMO. Shipping Hazards Coal emits methane, a flammable gas, which can create combustible atmospheres in transport. A mixture of air containing 5% to 16% methane is susceptible to ignition and constitutes an explosive environment. Additionally, coal may undergo oxidation, a process during which oxygen is depleted and concentrations of CO2 or carbon monoxide (CO) build in the cargo space. Some coals may react with water producing flammable and toxic gases, such as hydrogen, or acids which may cause corrosion. Lastly, coal is subject to spontaneous heating, which can lead to spontaneous combustion in the cargo space. This is why shipment of hot coal briquettes is forbidden. What is the Coast Guard doing about it? All vessels carrying coal are subject to Coast Guard inspection as part of the service’s responsibility to enforce maritime transportation requirements for all solid bulk cargo. The Office of Design and Engineering Standards (CG-ENG) at Coast Guard Headquarters creates and interprets domestic regulations related to marine trans- portation of coal and represents the United States’ views regarding international solid bulk cargo transportation at the IMO. Additionally, the Hazardous Materials Division within CG-ENG is responsible for reviewing and approv- ing Moisture Management Plans for solid bulk cargoes which may liquify or undergo dynamic separation, including coal. About the Author: LT Eva McNell is a staff engineer in the Office of Design and Engineering Standards’ Hazardous Materials Division. She graduated from the U.S. Coast Guard Academy in 2017 with a B.S. in marine and environmental sciences and holds an M.S. in environmental engineering from the Uni- versity of California, Berkeley. This office may be contacted at [email protected]. References: International Maritime Organization. (2023). International Maritime Solid Bulk Cargoes Code. IMO. United States of America. (2024). Title 46 Code of Federal Regulations: Shipping, Part 148 – Carriage of Bulk Solid Materials That Require Special Handling. Office of the Federal Register. United States of America. (2024). Title 49 Code of Federal Regulations: Shipping, Part 172 – Hazardous Materials Table, Special Provisions, Hazardous Materials Communications, Emergency Response Information, Training Requirements, and Security Plans. Office of the Federal Register. U.S. Energy Information Administration. (2024). Annual Coal Report 2023. https:// www.eia.gov/coal/annual/pdf/acr.pdf U.S. Energy Information Administration. (2024). Coal and Coke. https://www. eia.gov/international/data/world/coal-and-coke/coal-and-coke-production
