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how to compare wood pellets to firewood

Post in 'The Pellet Mill - Pellet and Multifuel Stoves' started by ugenetoo, Jun 27, 2008.

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  1. ugenetoo

    ugenetoo New Member

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    how many ton of premium wood pellets would equal a cord of seasoned wood?
    i would like to see the math, not a calculator.

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  2. AndrewChurchill

    AndrewChurchill Minister of Fire

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    General concensus is that 1 ton of pellets equals 1 and 1/2 cord of wood...... of course that figure depends on the species of wood.
  3. jimcooncat

    jimcooncat New Member

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    That's what I've been told as well. I just find it hard to believe that the same BTU's would take up a third of the space -- if my own math is correct.
  4. sinnian

    sinnian Minister of Fire

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    Pellets are 'compressed' and a lot lower in moisture then cord wood, thus the difference. Also, bags or bulk (bins) stack the pellets a lot closer then one can with cord wood. As to an actual mathematical figure in comparing the two, I have no idea.
  5. SteveT

    SteveT Feeling the Heat

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    In my opinion you can't compare pellets to cordwood with specifying the type of wood. Consider:

    Premium pellets are around 17 million BTU's per ton.

    A cord of pine is around 12 million BTU's.

    A cord of hardwood is generally between 19 million BTU's (ash) and 24 million BTU's (oak); maybe a bit more for other species.

    Sure, pellets generally have a better (more efficient) burn since they are low moisture (less heated water vapor up the flue). So you might adjust these "raw" numbers by a bit.

    But as a rule of thumb I'd say a ton of pellets is about .7 or .8 cords of hardwood and 1.5 cords of softwood.
  6. AndrewChurchill

    AndrewChurchill Minister of Fire

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    Don't forget they make both hardwood and softwood pellets so I'd say a ton of hardwood pellets should be equal to a cord and a half of hardwood. But some people claim that softwood pellets burn hotter than hardwood pellets.

    As a general rule one ton of pellets equals a cord and a half of wood.
  7. ugenetoo

    ugenetoo New Member

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    shouldnt be much difference between hw and sw pellets. after processing, the density is nearly the same. the only variable would be the amount of btus released by the pitches in softwood,which should be miniscule.
    ill try this myself. im sure someone will help me if im wrong.
    green hardwood pulp is being measured at 5000#/cord. usually runs about 45% moisture off the stump.so....5000x.55(%dry material) = 2750 dry material per cord. add back 6% for the m/c usually found in wood pellets...2750x1.06= 2915#.
    looks like 1 cord wood equals 1.46 ton wood pellets not taking into account the btu loss from the higher moisture of firewood.
  8. SteveT

    SteveT Feeling the Heat

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    I'd like to see the origin of this rule. Go to: http://www.consumerreports.org/cro/...ng-stoves-1-07/overview/0701_pellet-stove.htm. Part of this states that:

    According to the United States Department of Energy, the average cost of a cord of firewood or a ton of wood pellets is $190. But for a true comparison of the costs, you have to look at not just the price of the fuel but also the heating value of the fuel, also measured in BTU, and the efficiency of the heating appliance. Using averages for all three, the Energy Information Administration's Heating Fuel Comparison Calculator estimates it costs $14.39 to produce 1 million Btu using pellets and $15.83 using solid wood.

    The basis for the slight advantage (i.e around 10%) in the cost of pellets (per BTU) is that a pellet stove is typically more efficient. And that is an "average" cord. Compared to a ton of pellets there will be less heat delivered in a cord of softwood and more heat delivered in a cord of hardwood.
  9. SteveT

    SteveT Feeling the Heat

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    The calculation looks good but the cordwood to pulpwood change doesn't work. Pulpwood is harvested a small pieces (less sawing in making paper) so there is less air space in any volume. So the 5,000# per cord doesn't work. Here's a link that gives the weight by type of wood:

    http://extension.usu.edu/forestry/HomeTown/General_HeatingWithWood.htm. This shows that a cord of dry wood can weigh less than 2,000# on the low end to over 4,500#.

    With minimal variation a pound of any wood at the same moisture content contains the same heat energy as a pound of another species - it is the density (pounds/volume) that varies.

    And, softwood pellets burning hotter doesn't mean they give of more heat. It means they give of the same amount of heat in a shorter time.
  10. JustWood

    JustWood Minister of Fire

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    I have always said " A pound of wood is a pound of wood". Doesn't matter how big or small the pieces are it's how you regulate your stove and pull the available heat away from it. I always thought it would be neat to some how hook up a blower to a stack thermostat so that the hotter the stack got the faster the blower would run and pull or push the available heat away from stove and or stack into home to minimize heat loss up the chimney and maximize heat recovery.
  11. ugenetoo

    ugenetoo New Member

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    nobody sells wood by volume any more. its done by weight. thats the only accurate way to do it. pulpwood or cordwood. it doesnt matter. a cord measure is really an outdated form of measurment due to the huge number of variabilities.
    i guess i should have specified that, for accuracy, my green hardwood cord measures 5000#,which is how most people who process firewood have to buy their trees since we are all competing with the mills for product.
  12. SteveT

    SteveT Feeling the Heat

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    Are you sure about that? I am under the impression that in most areas it is illegal to sell to a consumer in any way but by the cord. Maybe weight is how the professionals sell to each other but I think "cord" is still the term of choice for sale to the end user.
  13. webbie

    webbie Seasoned Moderator Staff Member

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    Hardwood and softwood pellets are not different in heat value like firewood is....the reason is simple:

    Firewood is sold by cubic area
    Pellets are sold by weight

    A ton of wood is a ton of wood (in general) - most species having similar heating value.

    The correct answer to the question is: IT DEPENDS

    On a lot of things - but if I had to hazard an answer on the East Coast AND with a new efficient woodstove...

    It would be that a ton of pellets was about the same as a cord of medium mixed hardwoods. If a person had higher value heating hardwoods - then the ton would not even equal a cord.

    On the other hand, comparing on the west coast with soft wood.....the ton would definitely equal or exceed the heating value of a cord.
  14. webbie

    webbie Seasoned Moderator Staff Member

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    Math:
    One ton pellets at approx 7500 BTU lb dry weight heating value= 15,000,000 BTU
    burned at 73% eff.into house - about 11,000,000 BTU

    One cord seasoned mixed hardwoods 20% - weight 3200 lbs, heating value 6,000 BTU/LB = 19,200,000 BTU

    Heating eff. into home - 60% - about 12,000,000 BTU

    Close enough for rules of thumb.

    BTW, those also equate to about 100 gal. of fuel oil burned very efficiently - like at 85%
  15. SteveT

    SteveT Feeling the Heat

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    Craig is correct. I played around with a spreadsheet and tried to quantify it. What I came up with was:

    a. Of the 6 or 8 wood types I looked at, all contain about 14 million Btu/ton. VERY little variation.

    b. Using 17 million Btu's per ton as a value for pellets (somewhat higher than Craig's value) a ton of wood contains ~ 81% of the heat of a ton of pellets. (seems logical with the difference in moisture content).

    c. When looking at volume (cord) vs weight (pellets) there is no direct correlation. This is because a cord of wood can contain from about 16 million to nearly 28 million Btu's and weigh from about 2200# to 4000#. So a cord of white pine has only 94% of the heat of a ton a pellets, but a cord of locust has 165% of the heat of the same ton.

    These are "raw" numbers; if a pellet stove is more efficient than a modern (EPA) woodstove it would skew the numbers. But there is no way that saying a ton of pellets equals 1.5 cords of wood is valid. That would, for example, be saying 2000# of pellets has the same heat content as 6000# of locust.

    I think that saying a ton of pellets is equal to 1.25 tons of wood has merit. Maybe even 1.5 if the efficiency differences are large. But this is ton vs. ton, not ton vs. cord.
  16. RedRanger

    RedRanger New Member

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    Simplistic reply. but pellet without power means no heat. wood without power still lots of heat. but perhaps more work.
  17. MCPO

    MCPO Minister of Fire

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    Perhaps? I`d say definitely! And don`t forget to add the dirt, bugs, creosote , and a huge amount of ashes.
    John
  18. RedRanger

    RedRanger New Member

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    Well, I do recall years ago when the kids were little and the power was out for 3 days and we all moved the sleeping bags to the rec-room and slept there nice and toasty. Bugs and All!!!!
  19. MCPO

    MCPO Minister of Fire

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    A good point especially in rural areas. No question that it`s always nice to have a wood stove backup for heat .
    But for me in a situation like that I would run my smaller generator for the refrigerator and furnace utilizing 1 hr+ on and 4-5 hrs off cycles. In the past 10 yrs our power has gone off twice . Once for 3 hrs and once for 9 hrs.
    I`m not counting the other minor (nuisance) outages of an hour or less that happen each time a thunderbolt hits a transformer.
    But the fact remains that hundreds of my neighbors have managed to get along without a stove or generator through these outages and walk away none the worse with no frozen pipes either.
    Purchasing a pellet burner doesn`t alter the power outage situation for anyone using a central heating system anyway.
    John
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