UCG

Underground Coal Gasification (UCG) is a method of converting coal into combustible gas while the coal remains in place in the ground. In a UCG operation, wells are drilled into a coal seam from the surface or from a nearby location. Oxidants such as air, oxygen-enriched air, or steam are injected to ignite and sustain gasification within the seam. A separate pair of wells extracts the produced syngas, which is brought to the surface for processing, burning, or chemical use.

The produced gas, or syngas, typically contains hydrogen, carbon monoxide, carbon dioxide, methane, and other hydrocarbons. Its composition depends on the coal quality and operating conditions. The syngas can be used to generate electricity, serve as a chemical feedstock, or undergo further processing to produce hydrogen or other fuels. UCG can enable access to coal resources that are deep, thin, or otherwise uneconomical to mine, and it can reduce surface disturbance compared with conventional mining.

History and development of UCG dates back to early experiments in the 19th and 20th centuries. It gained renewed attention in the mid- to late 20th century through pilot and demonstration projects in various regions, including parts of the former Soviet Union, Europe, Australia, and Asia. Despite technical advances, broad commercial deployment has been limited due to concerns about controllability, environmental impacts, and regulatory considerations.

Environmental and safety concerns are central to UCG discussions. Potential issues include groundwater contamination from process fluids, subsidence above the burn zone, gas or liquid migration, and surface emissions. Effective site selection, well integrity, gas management, and long-term monitoring are critical. Regulatory frameworks often require comprehensive risk assessments and mitigation plans, as well as plans for post-operation stewardship.

As of the 2020s, UCG remains primarily at pilot or demonstration scales in several countries, with ongoing research aimed at improving controllability, gas cleanup, and integration with carbon management.