So... and I'm in no way a Memory Alpha-level ST nerd, caveat lector:

• transporters are matter-to-energy-to -matter transformers; which implies
• they have both energy-to-matter conversion technology, and matter-to-energy technology; which means
• assuming the conversion process itself isn't using vast quantities of energy, they could easily be turning energy into matter, and powering it with matter to energy, losing some energy in the conversion tax; which means
• they may as well be turning humanoid waste into food

It would imply that transporter and replicator technology are, basically, the same thing.

However, there are cannon issues.

• Even assuming metaphysics beyond what we know, they'd have to be violating the laws of thermodynamics to get more efficient energy production than matter-to-energy conversion. Which would make dilithium crystals and such less efficient than the technology they use to create food... so, why use it? Well, because
• The conversion process isn't low cost. They can transport people, and produce from from energy, but it's a super-expensive process. Like, you lose 90% of your energy in the matter:energy:matter cycle, out something. Which would mean
• Transporter technology isn't converting things to energy and back; it's using some cheat that does the same thing effectively, but with constraints, such as limits on how much you can alter the source object to destination object in the process; and getting pure energy out of matter is really lossy. But if you go from baseball to baseball, but in a different place, you avoid the energy penalty.

My head cannon is that this is how both replicators and transporters work. If you take a Riker and turn him into Riker somewhere else via a conversion loophole, it's pretty cheap. If you take a 236g of lead and turn it into a cup of Earl Grey (hot), it costs you some energy loss but you're using basically the same loophole. But if you try to turn Riker into pure energy to power the Enterprise because the warp core is offline, really you only get a couple of grams of usable energy because you can't use the loophole and most went into the conversion process -- which is why they still need an efficient fuel like dilithium.

Like, matter-to-energy requires antimatter, which is expensive to produce; but the loophole lets you skip over the antimatter part as long as, in the end, you have basically the same sort of matter.

The ethics of it are dubious because every time you see someone transport they are being literally killed in front of your eyes and a new copy created elsewhere.

They "nuh-uh'd" this in Enterprise. The inventor of the technology is introduced and basically says the people who propagate that theory are a constant thorn in his side, despite having no basis for it in the reality of that universe.

They also show people experiencing, and reacting to other things in, the matter streams during longer transports. Kind of hard to do if you're dead.