Because (1) the project would be designed seriously and (2) you don't need a completely closed loop. Just one that's mostly closed.
And then, once you've got it working well here on Earth, then you have a go at doing it on the moon.
This idea that the best place to get started on working out how to do these sorts of things is on the moon makes about as much sense as suggesting that the Space Shuttle program should have had astronauts rushing to work out the kinks of EVA missions in space instead of doing everything they could to test and practice procedures in swimming pools in an effort to learn as much as possible before you blow half a billion dollars on trying it out in orbit.
Agree. A moon base lets us test this out with real-world constraints as opposed to simulants.
We don’t know how to build ecological closed loops. But every failure mode of Biosphere 2’s was almost trivially solvable with expendable components. (The CO2 cascade being the simplest among them.)
> idea that the best place to get started on working out how to do these sorts of things is on the moon
It’s not. It’s the best next step. We’re doing a lot of pre-colonisation lab work already. And we will need to do more before establishing a moon base. The moon base is the interim goal—you don’t put astronauts in swimming pools without a plan for a Shuttle. And Biosphere 2 is a terrible swimming pool for anything we’d do on the Moon or Mars.
Ok so maybe a multibillionaire. Perhaps Elon musk? Yikes. Or Bezos? Maybe.
The EU is kinda busy increasing their defense spend, preparing to engage in Ukraine so I don’t see them super excited to do this.
China or India perhaps?
Also, why shouldn’t it be completely closed loop? If you’re designing to address the myriad of scenarios that can unfold in space, I’d say you’d want that experience under your belt. Its already easy mode doing this exercise on earth you might as well give yourself a little challenge to capture lessons learned.
NASA.
> why shouldn’t it be completely closed loop?
Because it doesn’t need to be. Engineering an ecological carbon cycle is hard. Putting in long-lived CO2 scrubbers is not.