How could humanoids master forge fire without using vegetal materials?

I'm building a fantasy world with a humanoid species (basically, "elves") which refuses to use dead wood.

Context

• They don't use dead wood because they don't want to. Consider that trees are sacred and should not be maimed or killed to create tools or materials and that even using wood from a tree which died from natural circumstances would be viewed as profanating a corpse.

• It is the same for bushes, grass, vegetal life in general.

• They live in big forests and use a very slow and meticulous kind of magic to gently bend tree branches into primitive houses. Then they use animal skins, feathers, silk and whatnot to create hermetic walls, for instance.

• They mostly rely on animal bones and organs and on rocks (eg silex) and minerals to create tools.

• They eat meat and fruits, which they collect from the trees with much respect and caution : they never eat more than half of a fruit and always put the seeds in fertile earth with the remaining portion of fruit, so that they have a good chance to grow into trees.

Problem

How could this species use fire ? They can't burn wood, obviously, and if lightning were to strike a tree and set it on fire, they could not use it because of the tree's sacredness (the elves would have to extinguish the fire to save the tree).

What kind of combustibles could they use, apart from wood ?

I would like them to be able to melt metal, so the fires should be extremely hot. And I would prefer not to have to resort to magic to make it possible (hence the science-based tag and not the magic tag), but a small bit of magic could be tolerable.

So far, I've thought of animal oil and lava, but I've been wondering if some people here could come up with better ideas, provided with references about whether their fires could melt metal.

Thanks !

EDIT :

My elves never ever used dead wood. They awakened before other intelligent species and never had the thought to use dead wood for their purposes. It would be about as alien as using a dead relative's body as a vacuum cleaner bag.

It is accepted to collect and eat fruits somehow like it would be for humans to milk wild cows (as long as you do not kill their offspring and you do not take all the milk from them) or to collect honey from wild bees.

Why is that so ? Mostly because of very strong religious / life-philosphy reasons. It has always been so and you cannot bypass such a strong tradition without becoming the public ennemy number one. Roughly : plants are sacred, you don't do them harm ; animals are not sacred, you can do whatever you like with them.

In present days, they are blacksmiths. I do not mind whether they have been so for very long, or if it is fairly recent because they heard of humans using metal and wanted to copy them, without sacrificing wood or plants.

How will I judge answers ?

• Obviously, no vegetal life should be harmed in the process and no dead vegetal material should be used in the process.

• The resulting fire should be able to melt at least some kinds of metal which are relevant to create tools : bronze would be enough, but you'll get "bonus points" if more resistant kinds of metal can be melted.

• The combustible / fire should be relatively easy to access. Using the heart of a star like Thor in Marvel's Infinity War could work, but my elves don't travel across space.

• The combustible / fire should be usable by many blacksmiths, in various places. A single great furnace like Mount Doom in the Lord of the Rings would not really suit my needs.

• The process should fit in a fantasy world. Tweaking with atoms and molecules would feel eerie - but well, if you can explain it in a convincing fantasy manner, that's okay.

• Using a small bit of magic is acceptable, but would result in "malus points".

• Scientific evidences and / or references regarding the fire viability (in itself and in a blacksmithing context) will get "bonus points".