There are a ton of places that claim to be sustainable, but everything about Japan's Methane Cafe, including its name, positions it as an eco cafe.
It's one thing to be conscious about recycling, but it's easy to waste energy by doing things like boiling excess water or using heat for longer than is needed. The members-only cafe in Osaki uses energy from kitchen waste that guests can bring in to boil their cup of tea. Instead of paying for a cup of coffee, this is a way to have the greenest tea around, without being needlessly wasteful.
The kitchen scraps are also used as fertilizer for crops, meaning that absolutely everything can be part of a cycle that's all for the benefit of the environment.