I propose a challenge to the community

I want to see a "green city" that works. Maybe try to find some optimal templates.

We don't have to call it that. But I would like to see more attempts at a few things I have yet to see players acheive:

Urban farming - a city that grows a lot of crops and has its own food factory. I have a template I am experimenting on for this but it is hard to keep everyone's needs in walking distance. I don't think it all needs to be grow in the city but the more the better. I currently am experimenting with small fields in residential areas to boost crop production. IMO if there is one industry that should be somewhat decentralized it is food. Greenhouse mods are acceptable although they are not up to date.

Cleaner(er) energy - making a power grid work with only renewables will be a huge challenge that I would love to see. Maybe there can be a limit for one nuclear power plant and bonus points if it's a single reactor, that way there is baseline power but I think you must have your own waste facility.

Waste obviously - recycle as much waste as possible. Incinerator power plants can be acceptable as a 'necessary evil' because, although they are big polluters, you still need a ton of trash for it to run at baseline and it would be irresponsible to export waste and make someone else deal with your trash.

Other than those 3 perameters it is up to the player what goes on in this green city, but the more self sufficient the better.

Please add any suggestions to this idyllic city challenge. I will work on my experiment as I have time and post about it when something is working.