Fusion is irrelevant as a practical energy source here on earth. The simple reason is that we already have all the "fusion energy" we'll ever need from that big fusion reactor in the sky... modern photovoltaics convert this energy to electricity at close to the same efficiency that you could convert the heat from a controlled fusion reactor to electricity. OK, yeah, photovoltaics still don't work at night, but there's a battery revolution underway that is solving that problem, and the two, photovoltaics + batteries, are already vastly cheaper than fusion can ever hope to be.

Fusion will be important for the future of humanity, especially in deep space, so we should keep researching and developing it. But it's not relevant to the climate crisis... the already existing technologies have that covered, we only need to deploy them faster.

Bye-bye microplastics: new plastic is recyclable and ocean-degradable

Depends on how you define feasible.

Take Wolfram's 1-dimensional cellular automata... some of them have infinite complexity, and of course you can "run" them for infinite time, and the "current" state is constantly expanding (like the Universe). So let's define "something feasible" as some specific finite bit pattern on the 1-dimensional line of an arbitrary current state. Is that "feasible" bit pattern guaranteed to appear anywhere in the automaton's present or future? I believe, and if I understand correctly, so does Wolfram, that for any reasonably complex "feasible pattern" the answer is no; even though the automaton produces infinitely many states, it is not guaranteed to explore all conceivable states.

In other words, in a given Universe (which has a specific set of rules that govern its evolution in time) even though there are infinitely many possible states, not all conceivable states are a possible result of that evolution.

TLDR: All energy usage produces waste heat, and while right now the planetary heating from altering the atmospheric composition (GHG emissions) dwarves that from waste heat, even if we were to switch all our energy production to "green" energy tomorrow, assuming continued exponential increase in energy consumption as at present, in one century waste heat alone would account for about 1K of planetary heating. Any technological civilization that follows a similar trajectory of exponential increase in energy consumption would make its planet uninhabitable within 1000 years.

Waste Heat and Habitability: Constraints from Technological Energy Consumption