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what will happen if you burn green wood

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by cvanhat, Aug 27, 2008.

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  1. cvanhat

    cvanhat New Member

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    in a eko gasification unit? will it hurt the unit or have people done it before? also is it nessasary to have a mixing valve in your system like the eko manual says?

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  2. webbie

    webbie Seasoned Moderator Staff Member

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    With green wood the unit will not enter into an efficient burn - it will smoke and steam, and you will get almost no heat from it.
    Doesn't sound like something that a person would want to do.....
  3. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    Burning green wood will tend to inhibit gasification. Doing it too often will lead to creosote issues, as the unit will be running like a conventional boiler, not a gasifier.

    If you have a small amount of green wood that you need to use, consider putting one piece of green wood in with a load of dry wood. If you run just green wood, or a large percentage of green wood, you will be asking for trouble...

    Yes. The cold water returning to the boiler will tend to inhibit gasification, and will eventually cause the boiler to corrode and leak. The mixing valve prevents that.

    You can use a pumped bypass loop, though, if you prefer.

    Joe
  4. dzook

    dzook Member

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    I did it for 4-6 weeks with my eko 60 or so before i knew better. well i was told i should have seasoned wood but just used what i used to throw in my heatmore. went thru more wood than my previous outdoor wood boiler during that time. almost impossible to gasify and will smoke a lot. what was worse the turbulors in the boiler heat exchanger froze with the added buildup of unburned smoke and i had to remove them (very difficult after they are stuck) clean the tubes and put them back in. it takes a day ot two to do that and is a real pain. i would have rather bought seasoned wood than go thru that again. i learned more about the insides than i cared to know.
  5. Nofossil

    Nofossil Moderator Emeritus

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    Craig and others are dead on. You must have really dry wood (<20%) to start the unit and get secondary combustion going. Once it's up to temperature, you can tolerate wood with up to about 30% moisture content, or even one or two pieces at 35% as long as you have some drier wood mixed in. Anything over 35% is not usable in my experience.

    There's a lot of sentiment that gasifiers are finicky and hard to operate. I think almost all of that comes from trying to get them to work with wood that's too green.

    One more caution: Don't do a load of all kiln-dried wood, either. The controller and air mixture adjustments are set up based on the expectation that the wood you're burning is well seasoned but air dried. Kiln dried wood can generate too much producer gas in the primary chamber causing 'puff back'. To some extent you can compensate by using larger pieces if the wood is really dry.
  6. cvanhat

    cvanhat New Member

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    well what would the moisture content be on a standing tree that is dead for example, or does everyone have to use the moisture testing tool?? i take it if your going to use a gasification unit you need to be two years ahead on cutting and splitting wood. what is your procedure. i remember my dad used to fell trees one year and let the sit, the next year we would block and split them and burn them that winter.
  7. Eric Johnson

    Eric Johnson Mod Emeritus

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    It's impossible to say what the moisture content of any dead, standing tree will be. It's all over the map, and likely very different from one part of the tree to the next. My rule of thumb for drying wood for a gasifier is that it should be cut, split and stacked for two summers, and covered or moved indoors for a few months prior to burning. The best way to determine moisture content accurately is with a meter. You need to split the wood before making the measurement, however, or you'll only read out what the surface mc is. Not the same as what's going on in the center of the piece.

    It's also worth noting that some species burn better in some gasifiers than others. In the case of the EKO 60, I've found hard maple to be the best.
  8. Adios Pantalones

    Adios Pantalones Minister of Fire

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    Some standing dead oak that I cut this year had pretty dry wood halfway up. At the base, however, actual water dripped out as the tree was tipping and putting pressure on the stump! The base was soaked. This was not "cellular" water, however, and the wood is dry some 4-5 months later.
  9. Nofossil

    Nofossil Moderator Emeritus

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    I broke down and bought a moisture meter, but that's not really completely necessary. Using the meter and paying attention to the boiler has helped me develop some rules of thumb.

    My experience is that dead trees can still have a LOT of moisture, and wood really doesn't dry much until you cut it.. I have some nice solid locust that was cut down 8 years ago (!) that's 35%.

    If you're planning for this winter, I'd buy enough seasoned wood to cover at least half your expected consumption. Stack and store covered, but in the sun if possible. As you cut your dead trees, do the same. There are a few months of good drying weather left. You should be able to mix your newly cut dead trees with seasoned wood and be fine.

    At the same time, cut and stack your wood for next year. I stack mine in an open area in east/west rows 8 feet apart, and put narrow tarps on the top to keep rain out of the center. The east/west orientation means that the sun shines on the south side of the pile, and the spacing keeps one row from shading the next and allows plenty of air circulation. If you can do something along these lines, wood cut this fall will be pretty good by next year. Ideally, you'd like to be two years ahead, but one year works if you can ensure good drying conditions.

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  10. heaterman

    heaterman Minister of Fire

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    My son in law used standing dead wood last year. It was cut in October/November and probably 80% of it was bark free, nice a gray and dry looking. On the surface it looked to be adequately dry but that proved to be far from the truth. He had all kinds of problems with his gasser. Wouldn't initiate secondary burn, gobs of creosote, turbulator cleaner stuck, poor heat output etc..... We were lucky if we could get 15 minutes of good clean gasification type burn out of a load.
    I stuck a moisture meter into the center of a split piece and it read 35%+. Testing of many more pieces revealed all the wood was well above 30% with a lot of it over 35. He shopped around for a few face cords the last part of the winter and although that stuff still tested between 25-30%, it made a world of difference. It was much easier to light, far less creosote, heat output was at least 50% higher. Enough so that he could heat his house and charge his storage tank at the same time. With the previous "green" wood it would not handle both loads.
    I'd have to say that if you don't have dry wood, don't bother trying to burn it. You'll be disappointed in the performance of your boiler, you'll basically waste 3/4 of your wood supply and to top it off you'll make a mighty mess out of your boiler. T'aint worth it my friend. Hunker down and buy some LP or oil this season. Wet wood is nothing but problems. You want to have 15-25% for best performance.

    JMHO

    PS the mixing valve is mandatory to prevent the water temperature in the boiler from dropping to low. Low water temp with no protection + unseasoned wood will lead to a completely plugged up boiler. Those two factors together are a recipe for disaster.
  11. pybyr

    pybyr Minister of Fire

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    It continues to fascinate me how extraordinarily different the various different tree species are not only in terms of initial moisture content, but also in terms of how fast or slow they dry, or what they do after they die and even fall over.

    For example, any of the birches (at least around this region) seem to be worthless within a few months if they die standing or are left on the ground- you can watch them rot as they stand there dead, and they don't seem to dry well (and again, rot at a fast pace) if laying on the ground.

    On the other hand, I have bumbled into a little hillside zone of a number of long-ago-fallen-over hophornbeam that, at first glance, looks like it would be good for nothing (back falling off, loads of moss on the exterior, etc) but after you cut through the first outer 3/8 inch, the inner wood is rock-hard, and seems, by the texture etc of the saw chips, to be bone dry. I cut one up about a week and a half ago, where the fallen-over stump was at the uphill end, and I cut my way from downhill end up to the stump. turned out the stump was hollow and suddenly wet goo came out all over my chain, boots, etc., but a few 18" sections downhill, the wood seemed absolutely dry as a bone.
  12. sweetheat

    sweetheat Member

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    any recommendations on wood moisture meters? I agree with nofo about orientation to sunlight. I've a row somewhat in the shade, it's moisture content is more than my rows in the sun. this winter I'll be firing the tarm 40 with storage tank. I think now would be a good time to bring wood into the shop. sweetheat
  13. pybyr

    pybyr Minister of Fire

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    I began to look into moisture meters a while back as I launched my gasifier project- but quickly came to the conclusion that the widely-marketed ones at consumer-type prices must be only vaguely accurate, given not only their price points but the variations in wood (decent meters allow you to calibrate or adjust for wood species and ambient temperature, each of which affect the electrical conductivity that these meters all measure)

    the lowest priced meter I've turned up yet that looks like it makes anything more than a pretense of giving you a reading that is likely to actually be precise (rather than just some fuzzy more-dry-vs-less dry reading that pretends to be some % based on who knows what assumptions or calibration), and to be able to factor in the species of wood, is the Delmhorst J-Lite, which seems to run in the territory of $140. That's expensive enough I have not sprung for one so far, and don't know if I could or would justify it. I'd be glad to hear of others worth thinking about that may cost less
  14. WoodNotOil

    WoodNotOil Minister of Fire

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    I burn a lot of dead wood. As stated by some above the first thing to look at is the amount of bark on the tree. The second thing is to simply look at and feel the end of a cut piece. If it is dry to the touch and looks checked or cracked near the center, you can probably burn it straight away. Typically the lower you go on the trunk the higher the mc will be. I find that even the wetter pieces of dead wood dry in a few months and may be usable later in the same heating season. I sometimes even dry pieces on top of my boilers. I burn a mix of seasoned wood and the driest of the dead wood I cut. So, you may be able to buy a little less seasoned wood for this year if you burn the driest deadwood along with it now and season the rest for later this winter or next season depending on mc. I guess my point is that there are a lot of variables, but that doesn't mean you wouldn't find some of it usable.

    Ash is a great wood for cutting during the winter as it is very dry when the sap is not running. The smaller parts of the trunk often have a low enough mc and so does the older rough barked branches (use the touch and dry cracked look test). Don't try to burn the smooth greener branches. The really big ash trees will have moisture in their trunks, but they can be cut split and dried for later use. Another advantage of ash is that the bark catches fire very easily. Don't cut ash while the sap is running during the summer unless it has no leafing at all as it is very wet inside and wastes time and space to dry it when it can be cut drier in winter.
  15. Dune

    Dune Minister of Fire

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    The drying time for firewood can be less than half, if one were to erect a simple tent of clear plastic over the pile. The plastic should end several inches above the ground, and should not touch the fire wood anywhere, but rather be held up by a framework of sticks. Green wood cand be burned in as little as five months using this method.
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