tion of about 1.3 Tcf per year in 2020 and 1.6 Tcf in 2030 (U.S. consumption is about 23 Tcf per year at present), which could offset the need for some LNG imports.
A related discussion is under way concerning the potential environmental risks of developing oil or gas resources in locations such as the ANWR-1002 area, the National Petroleum Reserve, or the formerly restricted OCS. Technology improvements such as long-reach directional drilling have reduced the area required by surface facilities for drilling and production, but some surface impact is inevitable. Similarly, the use of subsea completions for deepwater oil and gas production, pipeline delivery of fluids to shore in place of tankers, and attention to modern MMS environmental regulations governing platforms have reduced the potential for adverse impacts in offshore production. However, there will always remain some risk, whether at the platform or at the land end of the undersea pipeline. In addition, close-in platforms have visual impacts.
In addition to the OCS and federal land resources discussed in this section, the increased interest in natural gas production from shale formations may create a need to balance energy and environmental values regarding this resource. Large shale formations in the mid-Continent and the Gulf Coast (e.g., Barnett and Haynesville) are located in areas where oil and gas are currently produced. Infrastructure exists in these areas, and public opinion is probably open to additional gas production. However, the Marcellus shale in Appalachia is spread over a wide area, where lack of infrastructure and fragmented land ownership make production from this area more challenging (Snyder, 2008).
Table 7.12 provides estimates of coal resources by coal rank. Anthracite and bituminous coals have the highest energy and carbon content, whereas subbituminous coals and lignites have lower energy content and larger moisture and ash content (NRC, 2007, Box 4.1). The table indicates that the United States has about 20 years of reserves in active mines, but a much larger resource would be available for production if new mines could be opened and if the rail infrastructure required to deliver coal—or, alternatively, if sufficient long-distance transmission lines for delivery of electricity generated at the mine mouth—could be put in place. Costs of coal production vary widely with geographic setting and the type of mining, but it is clear that costs are low enough that substantial quantities of coal can be produced at current coal prices.