U.S. natural gas can easily replace Russian gas in Europe, the chief executive of EQT, the country's largest producer of gas, told the BBC in an interview. "We've got the ability to do more, the desire to do more," Toby Rice told the BBC, estimating that the United States had enough gas to quadruple current output by 2030. However, boosting exports of natural gas to Europe is not only a question of availability and willingness on the part of gas producers. There are other obstacles preventing U.S. gas from taking the place of Russian gas in Europe.…