There is no such thing as a ‘sustainable’ anything.
At some point ‘entropy’ takes over and it all falls apart......
“At some point ‘entropy’ takes over and it all falls apart”
Very true. Even at Galaxy scales. Mars had oceans and atmosphere.
At smaller scale, the notion of “sustainable” vehicles is utterly ridiculous. They wear out after 10 - 20 years and are scrapped. But weak, uneducated minds with zero sense of engineering are susceptible to ignorant non-scientific indoctrination. They blindly parrot the “sustainable” mantra without any basis for understanding what they are saying.