Philips Design has an interesting demonstration project called the “Microbial Home” that explores the use of methane gas and other natural end-to-end processes throughout the home.  As one part of the project, Philips proposes a lighting fixture that uses methane gas to feed bioluminescent bacteria.

If you can imagine a future where certain buildings are plumbed with a methane feed, which is quite reasonable in certain areas, this is actually a viable concept, at least for decorative lighting installations.