As estimates for the amount of U.S. natural gas resources have grown, so have the prospects of rising U.S. natural gas exports. The United States is expected to go from a net importer of natural gas to a net exporter by 2016. With recent natural gas prices relatively low compared to global prices and historically low for the United States, producers are looking for new markets for their natural gas. Projects to export liquefied natural gas (LNG) by tanker ship have been proposed-cumulatively accounting for over 60% of current gross U.S. natural gas production. Pipeline exports, which accounted for 99% of all exports of U.S. natural gas in 2013, are also likely to continue rising. However, under the Natural Gas Act, the Department of Energy (DOE) and the Federal Energy Regulatory Commission (FERC) must authorize the export of the natural gas commodity and related facilities, respectively. This overarching federal role in the expansion of U.S. natural gas exports has been the subject of ongoing oversight and debate in Congress. What effect exporting natural gas will have on U.S. domestic prices is a central question in the debate over whether to export. A significant rise in U.S. natural gas exports would likely put upwards pressure on domestic prices, but the magnitude of any rise is uncertain. There are numerous factors that will affect prices: export volumes, economic growth, differences in local markets, and government regulations, among others. Producers contend that increased exports will not raise prices significantly as there is ample supply to meet domestic demand, and there will be the added benefits of increased revenues, trade, and jobs, and less flaring. Consumers of natural gas, who also benefit from the current low prices, fear prices will rise if natural gas is exported. The DOE's most recent price study concluded that greater LNG exports "result in higher levels of real gross domestic product (GDP), which more than offsets the adverse impact of somewhat higher energy prices." Export opponents have been critical of DOE's conclusions. Environmental groups are split regarding natural gas use, with some favoring increased use to curb emissions of certain pollutants, while others oppose expanded use of natural gas because it is not as clean as renewable forms of energy, such as wind or solar. The use of hydraulic fracturing to produce shale gas for export markets has also raised concerns among environmental groups particularly concerned with its possible impacts on groundwater quality. The possibility of a significant increase in U.S. natural gas exports will factor into ongoing debates on the economy, energy independence, climate change, and energy security. Congressional interest has focused on the DOE's process and criteria for approving LNG commodity exports to non-free trade agreement (FTA) countries. Several bills in the 114th Congress would facilitate the approval of such permits. Both the House and Senate versions of the LNG Permitting Certainty and Transparency Act (H.R. 351 and S. 33), the Domestic Prosperity and Global Freedom Act (H.R. 89), and the Export American Natural Gas Act of 2015 (H.R. 428) would impose various deadlines on DOE export permit decisions. The American Job Creation and Strategic Alliances LNG Act (H.R. 287) would extend free trade treatment to World Trade Organization member nations with respect to LNG export permitting by DOE. The Crude Oil Export Act (H.R. 156) would repeal limitations on export of Outer Continental Shelf natural gas under the Outer Continental Shelf Lands Act (43 U.S.C. 1354). Other bills have been introduced that would affect natural gas production and infrastructure.