The production of shale oil has been hindered because of technical difficulties and costs.[46] In March 2011, the United States Bureau of Land Management called into question proposals in the U.S. for commercial operations, stating that "There are no economically viable ways yet known to extract and process oil shale for commercial purposes.In 2019, the United States produced2 about 19.25 million barrels per day (MMb/d) of petroleum, and it consumed3 about 20.46 MMb/d."[47]