Sunday, February 7, 2021

Combustion v. Capacity for Firewood: If it Burns, Burn it! Part Two


Some time back, I discussed the ways to properly burn really old wood, softwood that is seasoned, and less desirable hardwoods. Let's revisit that idea, as recently someone worried recently that I do indeed burn pine.  It can be safe to do, but you'll have to season it and burn a lot more wood in an year.  The numbers bear it out.

I will revert to my failed attempt to be an engineer, just for a moment.  Values follow for the combustion values of different types of firewood. Here are a few that I burn, copied from an excellent resource with many types of wood listed:

  • White Oak: 47.2, 4010, 25.7
  • White Pine: 26.3, 2240, 14.3
The first number gives density (pounds per cubic foot) of dry wood, the second the weight of a dry cord. The third measures heat value in millions of BTUs/dry cord.

A cord, incidentally, means closely stacked pile 8' x 4' x 4'.

Imagine a pile of logs, closely stacked, 32' long by 4' wide by 4' wide: four cords is what I project to burn by mid-March, when our heating needs ease to "morning and after dinner warm ups."  By early April, we'll stop. Yet we barely have enough wood in the barn, because we are home more, all day for me, during the pandemic. My wife retires this year, so next winter, she'll be around all day. 

 Where to find all those BTUs?

Hickory and Hornbeam are even better heaters than oak, but I don't have access to either in any quantity. Poplar, a common hardwood on our land, does not rate a listing but it's a light soft wood and closer to pine than oak. Maple, somewhat plentiful and Beech, more plentiful still, fall much closer to oak. Naturally, I try to mix in the softer stuff with the harder wood, to get the stove to its peak efficiency.

With pine, I need 1.8 cords to equal 1 cord of white oak, if I want the same heating value. Red Oak, a tree we have and I love to see in the forest for its stately height and shape, is not close to White Oak but more efficient than White Pine. Not all Pines are equal, either. Learning to identify trees provides a nice side-effect of learning to run a wood stove.

Firewood when purchased should be hardwood and seasoned, period. Don't pay for pine unless that's the only thing that grows in your area; many Canadians and Scandinavians have managed to stay alive for many winters burning it. I only use it because I cut so much of it, maintaining our property, often after a huge pine falls in a storm. Gradually, we are eliminating all pines on the edges of our roads.

For the outdoor fire pit? Pick up anything dry off the ground. Use what is left over in the barn. As farmer and friend Dominic, paterfamilias at delli Carpini Farms, likes to say "If it burns, burn it!"

Whatever the wood, the goals are simple when heating a building: avoid a chimney fire from creosote buildup and, as a distant second, not run out of wood. At worst, dealers will deliver but it's going to cost more in what passes for deep winter in Central Virginia. One retired neighbor runs a firewood business, but it pains me to buy wood.

Our house will stay warm (66-70 degrees downstairs, for us) if our stove shows 450-500 degrees F. Any green wood runs the risk of creosote, but seasoned Pine is no worse than any other seasoned wood if the stove maintains a hot-enough fire. Our evidence? Close inspection of the flue during our annual chimney sweeping.

This winter, not bitingly cold but consistently below 50 degrees, has meant that we have burned more wood than in any winter when we've been using it as a primary source of heat. 

I want to increase our firewood storage for 2021-22 by 50%; that's not a problem, as we'll just build a few more wood boxes outdoors for the fuel to season; my new run-in has other uses and is not ideal for wood storage. For the first time, I'm cutting down healthy trees, too, but I'm picking crooked and leaning ones and retaining straight trees that could make good lumber while providing shelter for animals. Another consideration nowadays, with climate change causing more frequent and more severe storms, has been to limit blow-downs and chain reactions when one occurs. That's a subject meriting a future post, but I'm still learning.

In our woods we have many small beeches growing right against each other, and I plan to thin several that are 30-40' tall this Spring. They will season for 9 months. As we fell pines, I factor in needing a lot more of it.  We cut 20 small ones in early Spring 2020, to fell leaners and clear thickets as we expanded our chicken run and dog run back into the shade of the hardwoods. That pine seasoned well but burned fast; I'd estimate we had a full cord of small pine logs in November but nary a stick now.

These lessons about woodlot management came from an expert. I heard Joel Salatin talk at length about the subject when we visited him at Polyface Farm. Joel took us greenhorns around in his woods and talked about how many rural landowners squander a renewable source of energy, shade, and wildlife habitat by not managing second-growth forest properly.

His woods look idyllic, but they are working woods. If you own woodland, go visit Polyface and see what Joel is up to. He's a character but every working farmer I know is one. Comes with the fresh air and woodsmoke, I reckon.

This year, when the stove is cold for months on end, I will be on the lookout for books presenting Earth-friendly, sustainable methods on managing woodland.