The Worm Farm
The building, called the "Worm Farm" would work like this:
It would have to ability to convert humus into it's next higher level, ie. premium humus to super humus, super humus to seaweed humus.
There might be, let's say, 5 levels to the building, each level allowing you to "upgrade" more humus at a time.
It would be made so that you might even lose some humus when you produce, for example, if you tried to convert 10 regular humus into 10 premium humus.
If you're lucky you could get 10 premium humus after the production time, or you might get back 7 regular humus and you end up losing 3 humus, or you might get 4 regular humus and 5 premium humus back.
The second part of the building is the one that actually has something to do with worms 
You'd be able to feed them kinda like in the cooperative goldfish pond, except with edge-plants, dung and leaves.
Let's say you start with 100 worms, AKA the "baseline amount", with 100 worms you'd have the baseline production time and the baseline chances for losing and/or not converting humus.
If you starve your worms (very bad!) they'll die (or something to that effect, as i'm not sure anything dies in bigfarm) at a rate of 1 worm/hour.
The lower the amount of worms the longer the production time and higher % chances of not producing and losing humus, the opposite it true for bigger amounts of worms of course.
To increase the number of worms, well, every hour that your worms are fed for more than 7 days in advance will give you +1 worms, as well, the worms will die of naturally at a rate of 21 worms/week (1 worm/8 hours) if you have more than 100 worms.
Of course, there'll be a limit to the number of worms you can have depending on the lvl of your worm farm (which would, by the way, be built on and solely on the main farm)
There is a possibility of 3 different types of worms, each specializing in converting either normal to premium, premium to super or super to seaweed humus, and each worm will be linked to either dung, leaves or edge-plants, though i think that's an idea for another day 
Hope you liked this idea, please give it a like if you do, and leave a comment if you have any suggestions, thanks for reading 
Comments
We do already get some humus upgraded with tractors, but something like this could be fun.
While I'm thinking about it, if (IF) they don't give us back the ability to make premium items in the lab, maybe they could do something like this for premium/super/seaweed feed and fertilizer too. Worms make sense for humus, not sure what character would be for feed or fertilizer, but I can see this idea expandable
Nice idea
Good points, great idea, thanks!
Thanks, "If you don't feed your worms, they'll escape to browner mulch piles/better soil"
True, that is possible, i wouldn't think that that's the only way we could get more imput though
Made by Jonquille6 (FR1)
True, good idea, i wasn't too sure about the seaweed, because it can be won in events quite a bit, as well as produced in the lab.
And, fair enough, you can produce premium and super of humus in the lab as well, but there's booster tokens competing for those catalysts
It's hard to predict what ggs will like/not like though, ggs aside, as you said, we'd all love it if we could produce seaweed humus through the wormform, thanks for the idea
Made by Jonquille6 (FR1)
And then, for all player is not easy to win seaweed topsoil if you are not in the first coop so this building does it justice between players in higher cooperatives and those who have not come this far.
Now we for HOPE GGS accept this good idea
And now that I thinking more about it I come to a good idea. GGS gives us back the normal lab as we all will have it and then instead make this worm farm with the catalysis and other things! What do you think?
Made by Jonquille6 (FR1)
FF is much better.
Or they could even give it its own space in the fishing area, worms/bait?