Sunday, December 27, 2015

handling firewood

Firewood will not be able to heat us all after the fossil fuels are gone, but with careful stewardship and fewer homes, it will be a way for many of us to keep warm in those places that get cold in the winter and have enough rainfall to grow trees.

For now though, I am lucky enough to be in a place where wood heat is feasible and sustainable for the local population density. The climate and terrain in Southwest Wisconsin are conducive to sustainable wood harvesting. 

I have projects in mind for improving the efficiency of our house, but in the mean time, we are burning around three cords of wood a winter. 

While splitting wood by hand, I often just kind of go blank, or "get in the zone", but the mind sometimes wanders. Can't tell you how many times I silently repeated that old saying "chopping your own wood warms you twice- once when chopping it, and once when burning it". Attribution is to many, but it's a pretty obvious conclusion to anyone who splits wood by hand.

But then I thought about how many times I touch the wood with my hand, ( and wearing out gloves) and began counting. After I drop a dead elm with my chainsaw ( not ready to use my crosscut on felling just yet, maybe next year) here are the steps to get in to the Russian furnace.
1. From the ground in to my truck
2. From truck to a pile next to the splitting station
3. From the ground on to the top of a big old oak round 
4. (smaller and more pieces now)From the ground to my wood shed
5. From my wood shed into a wheelbarrow
6. From the wheelbarrow in to a bin in our sunroom
7. From the bin in to the house and into the woodbox
8. From the woodbox in to the Russian furnace

and I guess we won't count the steps the ashes go through before they become soap or soil amendment.While the various handling steps don't wear you out like the actual splitting, they do make one appreciate how much time and labor we replace with fossil fuels these days. 

I was talking about firewood with a neighbor, and mentioned that I preferred not to use box elder because of the low btu content, and he stated that density and btu content are directly correlated, to which my immediate reaction was, gosh, that makes sense, but is it true? So I went looking for info to see for myself. Could find nothing on the internet that charted the correlation, so I found sources for various densities, and other sources for btu content, and graphed the two.

The chart below has density is in pounds (LBS) per cubic foot (FT3) and the heat content is in MBTU/cord. A cord of wood is a volume 4 feet by four feet by eight feet. Quite the mish mash of old units, but this doesn't really matter when looking for a correlation. 






In general, it is a pretty good linear relationship. Red cedar, apple, and shagbark hickory are the three that are a bit above the line, meaning that they have less btu content than one would extrapolate from their density. Shagbark hickory had the highest density, and also a very good btu content. Ironwood had the best btu content per unit volume, so it would be the best firewood to use, except it is less common, and does not grow to a large size. In my general area, oak is by far the most common wood for heating, as it has a good heat content, and is a common tree here. 

There are a few firewood or common trees for our area that I did not find numbers for, so this chart is of course not definitive, and I also can't vouch for the sources I used, but in general I think I've confirmed the  common sense notion that the density and heat content should have a linear relationship. Here is the data in tabular form. These are trees for the U.S., but I would imagine the relationship holds for other species.


alder
14.8
23.7
apple
21.6
46.5
black ash
17.9
32.8
green ash
21.1
38
white ash
21.6
39.8
aspen
13.7
25
basswood
13.7
24.8
american beech
22.7
40.8
blue beech
23.7
44.7
grey birch
19.5
34.4
yellow birch
22.1
41.7
white birch
20
37.4
butternut
13.2
25.2
redcedar
12.1
30.7
white cedar
11.6
19.6
black cherry
19.5
33.3
american elm
18.4
34.5
balsam fir
13.2
25.8
shagbark hickory
25.3
50.53
ironwood
26.4
47.5
black locust
23.2
44.2
honey locust
23.7
41.5
black maple
21.1
38.7
red maple
20
34
sugar maple
23.2
42.2
bur oak
22.7
41.8
red oak
22.1
41
white oak
24.7
44.3
jack pine
14.8
28.7
red pine
17.9
31.6
white pine
13.2
23.2

A final word for anyone heating, or contemplating heating with firewood- KEEP IT DRY! My pet peeve is heating with unseasoned or wet firewood. So much energy is wasted turning water to steam that it is a criminal waste, one might as well chuck half the wood you've worked so hard on into the nearest ravine. I see it all the time though, especially those who have the wood boilers.
The latest firewood shelter

I might rant on that another time, but for now, KEEP IT DRY!