This is not a chimney
These belching behemoths are cooling towers. In the UK's creaking, outdated power stations coal is burnt to heat water to steam. The steam is sent through turbines at high speed generating electricity. Once through the turbine a huge amount of energy remains in the hot water. For some reason the geniuses who designed these power plants decided that instead of using this heat for something useful like... er... heating they would call it 'waste heat' and fart it into the sky. Some power stations also fart the heat into rivers killing fish. Great move guys!