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Sustainable Planning for Wood Fuel Consumption

Posts: 110
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With the understanding that there is a large "unknown quantity" factor in this question, how does one go about estimating and planning for a consumption and re-growth rate for a sustainable woodlot?  I realize that the "unknown quantity" of the consumption rate will be the driving factor, but there are other factors that should be knowable, and those factors can be plugged into the planning function.

Let's use the Pacific Northwest as the location for starters (which is relevant to climate, wood species, etc.).  Here are some sample questions (feel free to add your own):

  • Are softwoods (fir, pine, hemlock, etc.) better to plan with than hardwoods (maple, oak, alder)?  They seem to grow faster, but do you get more energy out of the hardwoods, and therefore they are the better ones?
  • What about coppicing?  Maple can be coppiced well.  Is it a good forestry management technique?
  • If I harvest an acre of 40-year-old trees, do I get more than twice as much wood as I do from 20-year old trees? If so, that would seem to mean that I need to plan for either twice as much acreage of woodlot or half the consumption rate.  Or something.
  • If coppicing is used, how much wood can be harvested year-over-year per acre?

  • I realize that every answer here will have an "-ish" factor to it, and I'm really posting this here as a discussion topic rather than looking for a true answer.  Still, it seems worth discussing.
    Posts: 4328
    Location: Anjou ,France
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    AS someone once said if you want to go from there you don't want to be starting from here 😎
    A lot will depend on weather you are starting from a blank empty bit of land or an established forest or wooded area and what sort of house you are intending to heat and what sort of heating system you intend to use .
    Firstly l would think about having a home that is well insulated and efficiently heated . There are lots of threads on both these subjects on this site ( see rocket mass heated for example )
    Secondly can you get away with just managing the woodland by either copicing the trees you have already . I heat our house using the trees we have on our over grown site and looks good for six years without having to buy any wood . Remember that trees take years to be ready to do a first cut for coppice and there are many ways of coppicing depending on the type of tree ,see also stooling and pollarding There are many threads on this site dealing with this .
    Thirdly Hardwood is way way better than soft wood ,the latter is also problematic from the point of putting inflatable products in your chimney
    Fourthly the age of the trees is directly related to size but if you coppice the trees it will be likely to be less than every fourty years more like ten to fifteen plus there is the question of density as trees too close together do not grow well .

    If you have thick hedgerows where you can grow trees and use the land for another purpose ☺
    Posts: 1813
    Location: Zone 6b
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    I will second that a well built and properly installed RMH (Rocket Mass Heater) along with good insulation and perhaps earth berming, and a windbreak of trees, bushes, bales, or hugel to break the prevailing winds in the cold months.. will do a lot to reduce your wood consumption. Up to possibly 80% savings of what a regular setup would take in wood burned. You may need to add passive solar features as well, to bring that need for heating btu's down. So you may have to work backwards, from your heating source; then go forwards to your fuel supply. And go back and forth a few times to get it fine tuned.
    Posts: 4958
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    The best place to start anything sustainable, is to reduce the amount required. So many times I have seen people upgrade their heating appliance to insanely efficient models (that cost a lot), when they would have been far better off to invest in insulation, better windows, and plugging air gaps. To really do this, picture your home turned upside down, and anyplace that might leak water, is a place that is really leaking heat. Plug those areas first and that will go a long ways towards sustainability.

    Then get an energy efficient heating appliance. That may mean a rocket stove, or an more modern wood stove. Either way, with a tighter home, the appliance size will be smaller.

    Finally with the least amount of wood required, the overall land base to produce wood is much smaller making for much more sustainable. I can only answer this based on my location here in Maine, but here a woodlot grows 1 cord of wood per acre per year perpetually. In my case my home consumes 5 full cords of firewood per year, so I would need at least 5 acres of woodlot to sustain my heating needs. That means burning softwood or hardwood though. This is what a friend does. He has only 4 acres, burns 3 cord per year and has never run out of wood. He burns softwood and hardwood, right down to sticks, but gets by without cutting many live trees.

    The forester and I have deduced that wood losses on my farm, due to such things as rot due to maturity, windthrow (uproot), and broken stems, insect damage, etc amounts to about 3%. Since my forest averages about 30 cords per acre, I can glean about 9/10ths of a cord per acre just from damage. Naturally, trees do not live forever and some need culling, so additional wood can be used for heating purposes in a sustainable fashion.

    So by using an energy efficient home, with an energy efficient heating appliance, and the calculations I have done based here in Maine anyway, you can get an idea of what is needed to heat a home from wood perpetually.

    To manage all this, I have integrated an Excel Spreadsheet in with my foresters latest report (2014) and by charting growth, losses, damage and harvesting, I have a very accurate forest product inventory of what is on my farm. Since I can assign those forest products current prices, I can also tell what my forest is worth at any given time. It is a really handy tool.
    J.D. Ray
    Posts: 110
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    ...a woodlot grows 1 cord of wood per acre per year perpetually.

    Thank you for that.  I honestly understand completely the need for an efficient use of resources.  I was, however, just trying to get to something that I could use to project feed rate. It's not just about keeping a house warm; my mom's farm, which is 174 acres with over 100 in mature forest has plenty of wood.  I'm interested to know how much wood can come off of that farm sustainably to drive the energy needs of what I hope becomes a small scale industrial operation.  The farm came with a steam boiler that's sized large enough to drive quite a bit of machinery and develop electricity as a secondary function.  Waste heat can be used to keep things warm in the winter.

    So, with the question of "one cord per acre" answered, I can use the Engineering Toolbox to figure out how many BTUs per cord, and from there figure determine a heat rate for the boiler and how much useful energy can be developed, working back from that to figure out how many acres of woodlot we'll have to reserve for keeping the boiler fired.


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