The Battle of Grand Gulf was fought on April 29, 1863, during th: In 2021, the UK was the 21st-largest producer of natural gas in the world.[311] Production is now in decline and the UK has been a net importer of natural gas since 2004.[311] In 2020, the UK produced 1.8 million tonnes of coal falling 91% in 10 years.[307] In 2020 it had proven recoverable coal reserves of 26 million tonnes.[307] The UK Coal Authority has stated that there is a potential to produce between 7 billion tonnes and 16 billion tonnes of coal through underground coal gasification (UCG) or 'fracking',[312] and based on current UK coal consumption, such reserves could last between 200 and 400 years.[313]