Coal Types and Emissions

Not all coal is created equal. Anthracite packs 30 MJ/kg and is over 90% carbon. Lignite manages 15 MJ/kg at 25-35% carbon, with the rest being moisture and ash. Burning low-quality coal means hauling more mass, producing more waste, and emitting more CO2 per unit of useful energy.

Coal ranks from lowest to highest quality: lignite, sub-bituminous, bituminous, anthracite. Energy content roughly doubles from lignite to anthracite. Most US power plants burn sub-bituminous coal from Wyoming's Powder River Basin (low sulfur, moderate energy) or bituminous coal from Appalachia (higher energy, higher sulfur). The rank determines emissions per kilowatt-hour because lower-energy coal requires burning more mass to produce the same heat.

Compare emissions. A plant burning lignite at 15 MJ/kg emits roughly 1,000-1,200 gCO2/kWh. The same plant design burning bituminous at 27 MJ/kg emits roughly 800-900 gCO2/kWh. Coal quality alone shifts emissions by 20-30%.

Scrubbers remove 95% of sulfur dioxide. Can similar technology remove CO2?

Pollution control limits. Electrostatic precipitators capture 99% of particulates. Scrubbers remove SO2. Selective catalytic reduction handles NOx. But CO2 is the primary combustion product, not a trace pollutant. Removing it requires carbon capture, which imposes a 15-30% energy penalty. You can clean coal's air pollutants cheaply. You cannot clean its CO2 cheaply.

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