I found this list of firewood trees for zones 5 and up. Oddly neither Ash nor Elm are included, however, I cannot grow either tree because of Dutch Elm disease and Emerald Ash borer, which decimated all trees near me (Long Ialsnd, NY).
http://permaculturetokyo.blogspot.com/2006/05/top-10-fuel-trees-for-zone-5-and-above.html RANK NAME Heat/Cord
(Million BTUs)
1. Osage Orange (Maclura pomifera) 32.9
2. Oak, White (Quercas alba) 29.1
3. Locust, Black (Robinia pseudoacacia) 27.9
4. Ironwood (Ostrya virginiana) 27.9
5. Hickory, Shagbark (Carya ovata) 27.5
6. Apple (Malus domestica) 27.0
7. Honeylocust (Gleditsia triacanthos) 26.7
8. Hickory, Bitternut (Carya cordiformis) 26.7
9. Oak, Bur (Quercus macrocarpa) 26.2
10. Mulberry (Trees from the Moraceae Morus family) 25.8
WARNING: DO NOT plant the Asian / Russian white or paper Mulberries! They are devastatingly invasive! You CANNOT KILL THEM! The roots spread when you try; they take over EVERYTHING! One tiny piece of root destroys your compost pile and leaf mould. Even the most potent tree killing chemicals do not work (stump dies, roots THRIVE and SPREAD)!
Plant the native Red Mulberry or even the Black Mulberry – yummy berries and NOT invasive! The native red grows so fast – keep on top of it with pruning if you want a traditional tree! I haven’t tried coppicing them, but I can tell you that when I cut down the white one (hoping to kill it – BEFORE I knew how bad it was) within 2 weeks I had over 10 new shoots that grew into a shrub overnight; the next year they were at least 7 feet tall and FAT but the roots spread over 20 feet away into a new planting hole and took over the ENTIRE garden with little baby white mulberries EVERYWHERE – that’s when I bought the deadly chemicals and killed the stump – that only made the roots more determined to spread!
OK, sorry, that tree should be BANNED, it is so bad! Anyhow, as for how many trees to plant for firewood, that site says this:
“Now unless you’re a lumberjack, or semipro wood cutter, you’re probably wondering what the blazes is a DBH. That stands for diameter at breast height, taken by measuring a tree’s diameter at about 4 1/2 feet from the ground. Now, this list only goes up to 6 DBH for one reason. Most trees are coppiceable if they are less than 6 inches in diameter and less than 10 feet tall. Therefore, if we want the tree to survive and continue providing us with firewood in a sustainable manner, we don’t want to let it grow bigger than that. So, we will need, on average, about 34 of the above trees to produce one cord of firewood (if that is the amount you really need). I would suggest more, as we are going to coppice them on rotation. The average by today’s standard home (considering the average home is lacking sufficient insulation, has ceilings too high, and if it has a fireplace or stove, it’s inefficient) needs 4 1/2 to seven full cords of wood per year to heat. I will be bold here and state that this is probably due to the fact that modern structures aren’t built toward energy efficiency, and most people don’t burn wood that kicks out a high BTU. The common, lazy fire builder usually goes for lighter, faster burning woods.”
34 trees for one high-BTU cord. That's nuts! I burn 3 cords on average, but I don't start until the interior temp drops to 54 degrees.