Fall is in the air, and with it, firewood is on the minds of many North Country residents. Also with the season comes the annual deluge of "how to," "why to" and "when to" articles on heating with wood.
Reading them, and the BTU equivalency chart that seems to be an inevitable part of each, it's not hard to figure out that hickory delivers the optimum heat per cord burned, followed by oak and sugar maple. The logical conclusion one draws from the statistics is burn the best, though here is another sometimes ignored view of heating with wood: burn junk.
"Junk" is a loose term, open to interpretation. Although wood stove elitists might not burn elm or poplar, and consider it junk, it's still capable of keeping your house warm. Scrap pine, old fence posts and slab boards are considered by many to be junk wood, too, but there's no real reason they shouldn't comprise some part of your wood pile.
One solid argument for burning oak or maple versus species less valuable in terms of heat capabilities, is that if it takes the same effort to work up a cord of the former as it does the latter, why not take the best. That makes perfectly good sense if you have unlimited access to top quality hardwood. Furthermore, if you're paying a firewood vendor the going market price for a delivered cord, it's fair to expect maple, oak, beech and yellow birch.
On the other hand, property owners with two, five or 10 acres should think seriously in terms of culling less desirable trees, so why not burn poplar, birch and cherry while improving the woodlot's appearance and vigor. "Forty to 50% of most woodlots are trees of low grade quality," noted Carroll County Extension Forester Peter Pohl, "and they should be removed over a period of years. There's no reason not to burn that wood, either," he continued. "I've burned every type of wood myself, even pine. It's fine as long as you have a good mix."
Pohl makes a strong case for planned forest management, and urges land owners to be selective in cutting trees for firewood. "Many potential sawlogs are going for firewood these days," he said. "It's understandable since they're the easiest to cut and split. But good sawlogs are in short supply and great demand, and using potential stock for firewood is diminishing our resource base."
Even poplar, or "popple," can make decent sawlogs, Pohl points out, although the trees very often die before they reach suitable dimensions. Poplar is generally a much maligned species, as is elm, and both have a number of attributes. Although poplar rots quickly if left unsplit, cured properly it makes acceptable stovewood. Poplar fires tend to blaze up quickly, and it's a good choice to take the chill off a cold room. or to heat up the oven of the cookstove in short order. One of the disadvantages is that poplar leaves few coals, but that's why mixing is the key to burning junk wood. Get the fire started, and then throw on the longer lasting hardwoods.
Conversely, elm lasts interminably without ever bursting into flames, and some folks even claim it burns "cold." It's ideally suited for an extended, steady overnight fire, though. If you stuff the stove before heading to bed it will still be cooking in the morning, while maple or oak would have peaked out shortly after midnight.
There are several other likely sources of junk wood. The local dump is a good bet for scrap pine, and logging landings usually yield a good supply of butt ends. Many small mills still supply odd sized dowels, pine slabs or other scraps by the pickup load at a reasonable price, and some is still free. This is a particularly good prospect for renters and other non-land owning tenants who inevitably are looking for good "deals."
Before you seasoned-wood-burning veterans scoff at the idea of burning pine, consider that the dryness of the fuel is oftentimes more important than the relative BTU potential. Some softwoods may only have 60% of the heating capacity of hardwoods, but if that maple or oak isn't dry, the difference is far less. There are many reasons for creosote buildup and resulting chimney fires, but burning unseasoned hardwoods probably is the most common, not the consumption of dry junk wood.
Whether hard or softwood, heat value drops dramatically when the fuel is wet. Even split sugar maple left to dry in the open air for a year will retain close to 25% of its moisture, although it produces 21 million BTU's of available heat when burned in an efficient stove or furnace. Wet maple, on the other hand, offers only 18 million or almost 20 percent less heat. Dry white pine, however, promises 14-16 million BTU's. Seasoned elm 17.7 million, white birch, 18, and cherry delivers 18 million. Poplar brings up the rear with 12.5 million.
In the end, space may be the determining factor in how much junk wood it is feasible to burn in a season. If storage is a problem, top quality hardwoods are probably a better bet. A roomy woodshed, though, offers the chance to experiment, so why not fill a portion with scrap boards, old barn siding or fence posts this fall. The BTU value per board burned may not be as high as hickory or white oak (which is mighty scarce in the hills of New Hampshire anyway), but if the wood was gathers at a minimal cost while enhancing your property or cleaning up an old logging landing, this winter's fuel will be well worth it.