REUSES FOR MINED AREAS

When assessing a mined area, consideration should be given to potential uses of surface land or underground voids left by mining. In Indiana, more than 186,000 acres are underlain by underground coal mines; an additional 280,000 acres have been surface-mined for coal. Mining of other minerals has affected additional acreage. Large mined areas occur throughout the United States as well, and these hold great possibilities for conventional reuse, such as storage.

Opportunities for unconventional uses of mine voids should also be considered in mine and reclamation plans. Many mines are filled with water that is rarely suitable for humans, but could be used for biofuels production, in coal-to-liquid fuel (CTL) production, or integrated combined cycle gasification (IGCC) technologies, or for processing water in noncoal industries. Water is an excellent heat-exchange medium, thus water-filled mines could enhance geothermal systems or for use as heat sinks. Mine voids now act as de facto bioreactors and could be modified to become very large and efficient geobioreactors. A bioreactor can be any system that supports biological activity, but most are complex vessels that are highly controlled. They are used extensively in biotechnology to produce specialty chemicals in relatively small amounts. Geobioreactors are natural rock-hosted areas where microbes perform a desired function or produce a useful product. Some geobioreactors are known to produce methane from depleted petroleum reservoirs or in coal beds. Many mines could produce prodigious amounts of products.

Underground areas could potentially be used to store compressed gas for electricity generation or to store liquids and gases; exotic uses may even be possible. Careful consideration of geologic, hydrologic, and environmental details must be made to assure confinement of fluids, gases, or microbes to the proper void space before extensive use can be safely made. Certain abandoned mines, find industrial use, such as aquaculture, or as educational sites.

Mined areas offer great potential to address societal needs. Scientists, businessmen, and decision-makers should understand and make best use of the opportunities that mined spaces offer.