The replacement of Gas Lamps has been going on for a long time now.

There is a book that was written by H. V. Morton called "Ghosts Of London"(published in 1939) that mentioned the gas lamps being replaced.

This article is from 2014 and mentions both that book and the fact that there was still 1500 gas lamps in London. https://www.dailymail.co.uk/news/article-2848038/The-magical...

"They also burn a fossil fuel, which is more detrimental to the environment than low-power LEDs"

True however the true cleverness was that they burn the fumes coming off the sewerage system safely disposing of formally dangerous build ups of the gas while getting brighter at the same time.

So essentially fossil fuel is only a part of what they burn.