tinyurl.com/3b5bvq

Certainly. Only trouble I have with burnpile charcoal is the size. It's nice to have bigger pieces. Try screening it through at least 3/4" if not bigger mesh to get rid of the tiny stuff and ash.

Pecan wood is a traditional BBQ favorite. I don't know about maple though.

Also, to properly make charcoal you need a VERY hot fire in an enclosable space. I have done this before by setting some wood on fire in a hole in the ground. Let it burn until all of the smaller tinder is ash and you have some nice coals burning at the bottom of the fire. Then smoulder it by placing leaves and/or sawdust on top (this should create lots of smoke). Let the fire reignite the new tinder until you have a nice flame. When the flames subside a bit, stir it up (this allows the tinder and ash to penetrate to the bottom). After stirring and after the flames subside again, smoulder the fire again with tinder. Repeat this procedure until your' coals are swimming in ash. You now need enough rocks to cover the fire. You can test if you are ready for this by tossing one in from a few feet above the fire. It should create a nice cloud of ash. You want to carefully place the rocks on top of the fire as to keep the ash under the rocks. After the fire is covered with 8-10 inches of rock, let it burn until the rocks on top are too hot to touch. Then you want to bury the rocks loosly with earth. At this point, you have a very slowly burning fire that is well insulated. You should see very small amounts of smoke ecsaping from this mound of rock/earth. Leave it alone for a few hours and then pile some mud and/or wet clay on top to completely starve the fire of oxygen. You may not see smoke at this point, but do it anyway. Now let it sit for 8 hours or overnight. Now you can come back and dig up the goods. Just be careful as natural charcoal can be brittle.

They would burn up and not sustain heat I believe.