[joak]

Chemical energy. Like the plants, they take sun energy and store it as chemical energy. We could do the same, take CO2 and water and make CH4 and oxygen (electrolysis + Sabatier reaction) and make plastic. Or take ore, aluminum oxide and iron oxide, and "unburn" them releasing again oxygen (we already do that) etc...

We mostly use energy to manufacture things.

Life takes energy and lowers the entropy of the planet. Why shouldn't humans able to do the same? Any technical reason?

[AstralStorm]

There are limits to doing this, which is why we find it really hard to, say, remove CO2 from the atmosphere.

The technical reason is called entropy. Diffuse heat is hard to concentrate and use, much like gas outside of a container.

[codethief]

> Life takes energy and lowers the entropy of the planet. Why shouldn't humans able to do the same? Any technical reason?

Reducing entropy necessarily produces waste energy + entropy elsewhere. So the technical reason this cannot be done at the planetary scale is called Second Law of Thermodynamics.

Yes, we could try to put all that excess entropy & heat into space but there are limits to that (Stefan-Boltzmann law, among other things).