Presented by

Translate

Wednesday, December 28, 2011

"Green" Energy from American Elm and Green Wood

Winter has finally arrived here in central Pennsylvania. Thirty-two degrees today and the wind is howling. Time to break out the long-handle underwear and gloves.

I'm experimenting with my stoves again this year. Seems like every year I come up with something new to try. This year, I lost a big old American elm in the back of the house, and my friend Martin Melville came out and took the big boy down in a couple of hours. Martin is an artist with the ropes, and his manipulating those huge branches to avoid smashing in my roof was a thing to marvel at. He and I are the same age, and while I get dizzy pulling off my pajama bottoms in the morning, he's out there swinging around sixty feet in the air with a chain saw in one hand and a rope in the other. I think he missed his calling with the circus.

So, I get to experiment with this winter with American elm, which is something most folks these days don't get to do, since it is so rare these days. According to the nice heating value chart at Hearth.com, elm is about in the same class as the more common paper birch, cherry, and red maple; if you've burned those, you have a sense of what elm burns like. Pretty nice heat, but practically no coals in the morning. And it produces a light, white, fluffy ash, that both looks and smells like cigar ash. So, overall, not the greatest wood for the stove. And it's not great fun to split, either.

Another experiment this winter is mixing in various amounts of green wood. If you're new to firewood burning, you may have been warned about getting gypped into buying some green wood. Let me share another perspective on green wood.

First, if your supplier admits it's green, you should be able to get a good price on it. I'm burning a load of mixed green hardwood that Martin cut late in the year and dumped in my front yard about two months ago. I rented a hydraulic splitter, and bribed my seventeen year old son Jesse to hoist the bolts up to me; my six-year old son Wesley ran the switch (he works cheap) while I tried to avoid getting my fingers crushed by him as I turned the bolts. It all came together, and we had about three cords split in a couple half-days of work together.

Well, back to it's being green. Since it was, Martin gave me a good price on it...real good, considering it was mostly rock and red oak, with some maple. And this stuff green is about as heavy as gold or lead...so you might thinked I'm screwed if I have to burn it this year.

Not so. What I do is get the fire going real good with some dry wood, and then feed in the green stuff according to a rate the fire can handle. In effect, I'm using the moisture in the green wood to damper down the fire, instead of using the damper rod to cut back on the oxygen flow to the fire. True, in the process of doing so I'm effectively reducing the BTU value of the wood, because energy is being consumed in volatilizing the water and sending it up the chimney as steam. But, the heating time per stick of wood is being extended because the wood burns slower, and my efficient stove can still blow you out of the room with green wood, if you want it to. Once it gets below 20 degrees outside, though, I'll probably need a higher ratio of dry wood to green to keep the rooms toasty.

Back in the days of the open fires, folks used to appreciate the sizzle that green wood put off. Here's a video I shot last week of some of that real green wood once it starts to heat up.



And I shot this next video about a half hour later. You can see the stick in the middle is really burning now, and the entire end of the stick is wet as all the water is being chased out. Believe it or not, wood this green will keep sizzling until it gets completely charcoaled.



Oh, that's another strategy for green wood. One thing that works well is to get a great fire going just before bedtime, then pack your stove full of green wood and damper it all the way down for the night. In the morning, you'll have nice dry charcoal that will produce a great hot fire for your tush in just a minute or so, once you add another piece or two of wood and crank the air to it.

So, part of being a firewood aficionado is understanding your stove, your heating requirements, and the trade-off in heat produced by different species of wood and different degrees of "green". The fun is in the learning. Stay warm!

2 comments:

Fireball Doowah said...

I missed this post on 'green wood', you latest post brought this one to my attention... So, the question is, in Puget Sound, we have air quality issues, particularly on the occasional cold clear days (when the wood stove is most needed). Does green wood increase fine particulate matter? I've had "burn dry wood" drilled into my head, and have mostly not burned much green wood, but I'm curious if one can make the fire hot enough such that burning green wood does not release too much particulate?

Chuck Ray said...

Green wood will result in more particulate being released, as the lower stove temperature results in less complete combustion, and the rising steam carries these un-combusted particles with it. So when you add green wood, your smoke level goes up accordingly, similar to when you dampen the stove.

You're correct, the trick is to maintain a high stove temperature, and you can do that to a certain extent by reducing the green/dry ratio. The best way to do that is to split the green wood into smaller pieces, and feed them more frequently. This will damper the firebox less and put less smoke up the chimney.

But yes, in general, burning green wood reduces the quality of your stove emission.