Coal mining: Techniques
Longwalls, draglines and the blasting of whole mountaintops
What this tab covers The methods used to capture this energy: how each works, and how they compare on efficiency, cost, life-cycle emissions, maturity and scale.Coal is mined underground (longwall or room and pillar) or from the surface (strip and open-pit mining), with mountaintop removal as an extreme surface method. About two-thirds of US output comes from surface mines.
Comparison
| Method | Efficiency | Cost | Life-cycle emissions | Maturity | Scale |
|---|---|---|---|---|---|
| Underground mining (longwall and room and pillar)1457836 | 62% (room and pillar) to 78% (longwall) of minable coal recovered; 3.24 short tons per employee hour (US, 2024) | USD 85.88 per short ton average sales price (US, 2024) | Coal mining emitted 43 Mt of methane (2025), mostly from deep, gassy seams; coal power about 820 g CO2e/kWh (IPCC median) | mature | About one-third of US output; world coal production 9.1 billion tonnes (2024, all methods) |
| Surface (strip and open-pit) mining1453 | About 92% of minable coal recovered (contour strip); 8.94 short tons per employee hour (US, 2024) | USD 29.61 per short ton average sales price (US, 2024) | Less methane than deep mines; diesel for haulage is the main direct source | mature | About two-thirds of US output |
| Mountaintop removal39 | No separate figure in our sources | Included in US surface prices above | As surface mining, plus carbon released from cleared forest and soil | mature (declining) | 2,040 square miles of Appalachian forest cleared (2010) |
Surface mining is cheaper and more productive: US surface mines produce almost three times more coal per worker-hour (calculated) and sell it for about a third of the underground price, partly because western surface coal has less energy per tonne. Underground mining leaves more coal behind, is more dangerous and releases more methane, but reaches deep seams. Mountaintop removal has the largest surface footprint. Whatever the method, burning coal, not mining it, dominates its climate impact.
How each method works
Underground mining (longwall and room and pillar)Tunnels or shafts reach the seam. Room and pillar mining cuts rooms and leaves coal pillars to hold up the roof; in longwall mining a shearer moves along a long face under advancing hydraulic supports, and the roof caves in behind.1457836
Surface (strip and open-pit) miningOverburden (rock above the seam) is blasted and moved by draglines, shovels and trucks, the coal is dug out and the overburden put back in the previous cut.1453
Mountaintop removalForest is cleared and explosives remove a mountain top to reach thin seams; surplus rock is dumped into valleys as valley fill.39
Sources
- Coal Resource Recoverability: A Methodology (Information Circular 9368; Rohrbacher, Teeters, Sullivan and Osmonson), Table 12 US Bureau of Mines (hosted by USGS), 1993
- Coal explained: Coal mining and transportation US Energy Information Administration, 2025
- Annual Coal Report, Table 21: Coal Productivity by State and Mine Type, 2024 and 2023 US Energy Information Administration, 2025
- Annual Coal Report, Table 28: Average Sales Price of Coal by State and Mine Type, 2024 and 2023 US Energy Information Administration, 2025
- Coal 2025: Supply International Energy Agency, 2025
- Global Methane Tracker 2026: Key findings International Energy Agency, 2026
- Climate Change 2014: Mitigation of Climate Change, Annex III: Technology-specific cost and performance parameters (Table A.III.2, life-cycle emissions) IPCC Working Group III, 2014
- Mountaintop mining consequences (Palmer et al., Science 327(5962): 148-149) Science (AAAS), 2010