I did not know you could "grill" vine or willow twigs. I take it you didn't actually mean a grill like you cook on. you said firing. do you have a kiln or do you use some other method. I have a willow tree and would like to just cut some off and "grill it up" and make my own charcoal. I would like the kind that actually has the knots in it. gives it that old-fashioned old world look.
can you do your own compressed charcoal? if so what would you bind it with.

Here is the answer to Larry's question:

I just found your comment now and your question about how to grill willow charcoal. You must first cut up a bundle of twigs, try 8" or so. Then wrap in multiple layers of aluminum foil. You need to get it pretty tight. Then put it in the coals, even put extra coals on top. You'll need a small vent hole through the foil. A few toothpick holes. The idea is to combust it thoroughly, but not allow oxygen. Watch the smoke coming out. It will change colors, getting clear at the end. Depending how hot your fire is, it may take several hours. You could even leave it overnight in a covered grill. You could also use a kiln, but it might stink it up. When you cook it right, you will get the knots and all.

I am Charcoal man!