What tree species gives the most BTUs per acre per year?

[wolfram]

I know that a precise answer is not possible given incomplete info, but please hear me out.  A question came up regarding planting trees for firewood production (in North America).  If one wanted to maximize the number of BTUs per acre per year, what species should one consider, all else being equal?  An important consideration is the shortest time to first harvest.

Cost per BTU is not a factor in the discussion.  In other words, low-density species, which may take more effort to handle, are fine.

Thank you.

[beenthere]

wolfram
Good friend of mine bought some WI property in '72 and after some intense research of just what you are asking, he planted soft maple (I believe it was silver). You might look at red maple. It is higher density than silver.

That decision was based on fast growth and wood density.  He was after 6 cords of wood a year, and planted aout 10 acres. He has since passed, and I don't think he realized any harvest of wood from that planting.

[Dodgy Loner]

That is an excellent question, and although I do not know the answer, I do believe that the question can be simplified somewhat. Since all wood has the same number of BTUs per pound, all you really need to know is what tree species would produce the most tonnage per acre on a dry weight basis per year.

I am familiar with one study on the Savannah River Site in South Carolina that determined that of four fast-growing species - loblolly pine, tuliptree, eastern cottonwood, and American sycamore - the American sycamore produced the most tonnage per acre on a dry weight basis. Sycamore was also considered desirable because it can reproduce via coppicing. The study was for a biomass energy source.

[Tom]

What is coppicing?

[Dodgy Loner]

Coppicing is a method of allowing a forest to reproduce by stump sprouts after harvesting. It is a traditional practice in Europe, where coppicing systems were, and in some areas still are, used to keep vigorous young stands of hardwoods for thatching spars, hurdle-making, wicker work, firewood, and charcoal production.

[Ron Wenrich]

I saw one operation where they coppiced ironwood in the understory and were getting firewood every 20-30 years.  It was in Germany and was grown underneath white oak and beech forests. 

Pine has a higher BTU value/lb than hardwoods.  8800 for pine and 8000 for hardwoods (if memory serves).  The higher pine BTU was due to the volatiles.

For the biomass market, they always pushed hybrid poplar and willow.  They grow fast and can yield 3-6 dry tons/yr.  Native hardwoods are rated at about 1 dry ton/yr.

[Ianab]

Problem is that for Firewood production, the fastest growing trees like Cottonwood, hybird poplar, willow and pine are less desirable to sell.

If you are dumping truckloads into an industiral size power plant then it doesn't matter what the species is, you jsut want the BTUs

If you are selling it as firewood, people tend to want hardwood, so the Soft Maples and Sycamore might give a better return, even if it was technically less wood. The ability to coppice them could increase your production once the trees are established.

Ian

[SwampDonkey]

Red maple coppices very well and grows fast. Sugar maple and yellow birch, not so great. Beech will, but dies before it reaches any size, I've never seen it grow a good sized stem like a red maple sucker will. Beech has been cut for firewood for years here and you just don't see the suckers get big, not even 5 inches.

[wolfram]

Great responses!  Exactly what I was looking for.  And super fast too!  Thanks.

Dodgy, I agree with your restatement of the problem.  I was not aware of the SC study or about Am. Sycamore.  I would like to learn more. 

Ron, thanks for the info on hybrid poplars.  It appears (from some initial google-ing) that they can be coppiced too.  Based on your comment about the biomass market, can I conclude indirectly that the hybrid poplar's annual BTU yield (per acre) is greater than pine's?

Ianab, I agree about the low desirability of the quick growing species in relation to marketable firewood.  Your second sentence describes my interest area almost perfectly.

SD, I have some red maple that I coppice for fun/experiment.  You're right, it's great stuff for that.  If it weren't taking over my woods, I'd love the stuff!

Others up this way keep telling me about black locust.  While a great firewood and a good grower here, it is hard for me to believe that it puts on BTUs as fast as the species that y'all are discussing.  Any thoughts on this?

[SwampDonkey]

Up here, where black locust is not native, it grows very slow. I see it sometimes on abandoned home sites and it's not very big.

[Ron Wenrich]

I would think that the hybrid poplar would yield more than the pine, especially in NY.  I have yet to see anybody that has mentioned pine as a species for biomass fuels.  All the studies suggest the hybrid poplar, willow or cottonwood. 

There was a study at Penn State back in the late '70s where they were looking at cutting poplar every 5-10 yrs and bundling the material.  I pretty sure that coppicing was being used as a reproduction method.  But, energy got cheap and that was put on the back burner.

If you're looking at biomass, I saw a figure of 11 tons/acre with switch grass.  A lot depends on what you're looking at doing with the material.  Pellets would be a nice fuel to make with the low density stuff. 

[WDH]

Switch grass is more like 6 tons/ac per year from what I have learned.  I guess that it depends on the quality of the site.

[Phorester]

I'd vote for black locust. 

[clearcut]

I worked with Eucalyptus plantations in California using short rotation (7 years) intensive culture  (drip irrigation and fertilizer) that were producing 6-10 cords per acre per year. Average DBH 4.5" and height of 44 ' with a dry weight of 87 tons per acre. BTUs similar to oak.

   http://ucce.ucdavis.edu/files/repositoryfiles/ca4206p19-68813.pdf

[Ron Wenrich]

Switch grass is more like 6 tons/ac per year from what I have learned.  I guess that it depends on the quality of the site.

Auburn study.  http://bioenergy.ornl.gov/papers/misc/switgrs.html  They even said they got 15 tons/acre the one year.

[wolfram]

Phorester, thank you for the vote.  Please substantiate.  I am looking for pertinent facts on black locust.  Thank you.

[Phorester]

Your question didn't stipulate what use the firewood would be grown for, so that might change my answer.  My answer was for growing firewood for home heating, or for a firewood producer to grow a crop to sell for the residential market. 

Black locust (Robinia pseudoacacia) is consistiently in the top of every list I have seen over the years for BTU production. It ranks up there with white oak and hickory.  But locust grows faster than the other top ranked tree species.  On just about any site that will grow hardwoods you can get 6" diameter trees in 20 years with black locust.  Faster growth in better soils. For oak and hickory you're looking at 30 years or more for the same size tree.

Other tree species like maple, poplar, sumac, can grow faster, but their BTU rating is much lower than locust.  That means that you have to grow, cut, handle, store, and burn twice as much wood to get the same amount of heat as with black locust.

So black locust gives you firewood sized trees in the shortest time, and with more BTU's per tree than about any other species.

Another source for more firewood info including a list of BTU production by tree species is:
http://forestry.about.com/od/firewood/a/firewood_chart.htm

[Dodgy Loner]

Other tree species like maple, poplar, sumac, can grow faster, but their BTU rating is much lower than locust.  That means that you have to grow, cut, handle, store, and burn twice as much wood to get the same amount of heat as with black locust.

You are right about this, Phorester, but wolfram mentioned that cost/BTU was unimportant in his intitial post:

Cost per BTU is not a factor in the discussion.  In other words, low-density species, which may take more effort to handle, are fine.

[tonich]

Coppicing is a method of allowing a forest to reproduce by stump sprouts after harvesting. It is a traditional practice in Europe, where coppicing systems were, and in some areas still are, used to keep vigorous young stands of hardwoods for thatching spars, hurdle-making, wicker work, firewood, and charcoal production.

The coppice system occurred to satisfy mainly the demand of  firewood and charcoal, requiring little or no silvicultural skills. In the middle ages it was commonly spread silvicultural system. However, in terms of sustainability and longlivity, nowadays new forester's challenge is the conversion back to their seed origin, which also will bring the opportunity to produce quality big timber . For example, the main longterm goal for over 80 % of governmental low-steam forest in Bulgaria is turning back to high-stem ones, mainly by shelterwood and selection approach.


Among the all coppice systems, Coppice-with-Standards management is an outstanding one.

Te coppice-with-standards system was presumably developed in France, where it was designed by J. B. Colbert for Louis XIV, king of France, between 1664 and 1683. Te aim was to fulfl the triune function of the king’s forests: (1) production of strong oak trunks used for building and navy, (2) production of frewood and timber, and charcoal, (3) pig grazing on acorns from the mature oaks of the top stand layer. Te features of the coppice-with-standards silvicultural system with prevailing oak in the top layer and coppice in the bottom layer proved very interesting from an economic point of view, and the coppice-with-standards form remained in use in many foodplain forests of Central Europe until the first half of the 20th century (Mezera 1956)

Did some further search and found an article from an American author, stating British Isles as an origin of the method ( ). Nevertheless this confusion, the article is descriptive enough:
http://www.agroforestry.net/overstory/overstory47.html

[ford62783]

i also agree on the black locust for the fastest and most btus per ton though if time was not a major factor i prefer beach though it dsnt have the btus that white oak and locust have i use it almost exclusively d to the availibility and the price per kbf isnt great

[SwampDonkey]

Beech, hard maple, and yellow birch all about the same up here. But all are very slow growing after pole stage, due in part to the fact that no one thins hardwood past pre commercial stage to develop into logs. Or at least nothing significant. We used to have a government program to treat young hardwood past pole stage, like a timber improvement. It was always directed toward the best sites, which were assessed on basal area, height, and quality of the stems before any treatment. No sense in treating junk to grow logs, junk remains junk. Had to be so many crop trees released on at least 2 sides per acre or hectare. Very few sites got done because the best hardwood ground is now farms and those ridge tops around here look nice in the fall, but only sheltered gullies would produce decent logs. The rest grew "apple trees" and then the ice storms and wind did their number.

One land owner told me, "I'm not interested in growing apple trees"

[Phorester]

"You are right about this, Phorester, but wolfram mentioned that cost/BTU was unimportant in his intitial post...."

Correct, DODGY.  But he asked why I suggested black locust, and that was my answer.  But I qualified my answer by saying was in light of residential heating. 

At some point, unless his question was just a hypothetical exercise, production costs of time and money will have to be considered.   

[wolfram]

The application that prompted the question is residential energy production for a small community.  Like Phorester says, economics always matter in the end.  However, if there were an abundance of willing and "free" man hours in the community, the marginal cash cost to plant, harvest, & maintain is low.

If a dense species (e.g. Black Locust) and a low-density wood (e.g. Hybrid Poplar) produced nearly the same annual BTUs/acre at the site, then the dense species would win, all else being equal.  Essentially, I am attempting to do an economic analysis that favors minimizing lead time and requirements for annual cash outlay.

Now, where did all of our free workers go....?

[Phorester]

Ahh..., now we have more info for a better way to answer the question.  But that begs the need for more info....
Are you talking about heating individual houses, or a generating plant to provide energy to lots of houses?  And if the latter, I'm guessing that you mean electric power?  Not steam, hot water, etc.

For individual home heating,  I'd still investigate black locust. Mainly because appliances already exist for burning wood for  heating an individual house (stoves) and black locust grows fastest (at least in my area) and has the most BTU's in the shortest time.  For a community power plant, I'd go with a tree that could be coppiced on a short rotation, or investigate  switchgrass (already suggested) which all research so far says will produce more BTU's per acre than any tree species. Pros and cons for both.  Also, look into trees that are already growing in forests in your area.  Here, we have an abundance of red maple and ailanthus saplings and small trees that could be harvested out of existing forests that would increase growing space and therefore improve the health of higher value hardwoods like oak at the same time.

Build the power plant to use whatever fuel you're producing for it.
 

[Tom]

Just an off-the-wall thought, but it might be advantageous to consider the length of time that the site can produce a crop, in sufficient quantities of product.

As the bio-mass is removed, so are the nutrients in the soil.  "Fines" (twigs and leaves) are said to contain most of the nutrients and they will be returned to the soil, except for the switchgrass scenario, and the land could be amended.

An example of the results of depleting the soil already exists in the history of the American Dust Bowl and  considerations are currently argued with the production of Pine Straw Mulch.

As far as the labor is concerned, there are already examples of failing communes.  I offer that term differently than the word community, in that I see the free labor eventually being at odds with each other and the management.  One will not produce enough. One will produce more than he thinks he is getting and one will not be able to produce as much as he needs.

[wolfram]

Thank you again for the help.  The initial question came up here in the context of farming sustainably for firewood to heat individual homes and businesses, within a small community.  However, I was trying to extend the thinking to cover a potential future case of the addition of a few small centralized facilities in town for power generation and heat.  Like most things, the best solution depends on a proper statement of the problem.  Sounds like those are two different problems to solve.  That's ok, since solving the first one would not preclude future action on the second.

Regarding logistics, the thinking was to have one set of fixed expenses for fuel production on a controllable nearby site.  Farm labor would come from members, with proper incentives and a component of charity in place.  It would have people problems for sure.  And we have a good share of those already!

[Ron Wenrich]

That context takes on a whole different set of parameters.  If you're looking at producing power, you have a variety of fuels you can use.  I helped to place one of those a few decades ago, and we used a lot of wood waste.  Things have come a long way since then. 

But, the thinking is you need a use for your trash steam.  That's the co-generation part.  On my project, we used the trash steam for cooking tomatoes in a factory setting.  There are other settings you can use such as heat for schools, hospitals, community buildings, and anything else that would use steam for heating or cooking.  You also need a source of water.

Our project used a combination of sawdust and wood chips.  If you are looking at growing biomass for fuel, then you want the fastest growing material, not necessarily the densest wood. 

Other fuel inputs could include construction waste, garbage, and other burnable by products.  For waste material, you often can charge a tipping fee. 

If you are generating power, you should be able to make it a money making project and the need for volunteers would be minimal.

[Phorester]

My personal experience and observation with volunteer groups, homeowner associations, and the like is that the initlal enthusiasum and desire to do the work fades away over a few years as the first bunch of people gets older, moves away, gets tired of the extra effort they need to make, looses interest in it, etc.  Then the next wave of people feels that it is a burden and not a labor of love.  Then that community demands that the local government take it over, which they do, with an increase in everybody's taxes, of course.

So I'd suggest setting it up initially to have it a money making proposition as Ron suggests, or at lease break-even, with a core of hired people to do the majority of work, and volunteers as an additional but not necessary source of labor. 

[SwampDonkey]

People being as they are, I would have to agree with Ron and Phorester. You'll never maintain the harmony unless there is a lot of ignorance, innocence and isolation. And I can quote two well known instances.

[nb_foresttech]

Thought I might throw this one into the mix. So many variables with site and genetic stock that there probably isn't a right answer. In the right site Tamarack might offer an alternative. It's best traditional growth is in the Great lake states. It certainly isn't at the bottom of the BTU list and grows fast. Easy to manage and has few pests. The following is a highlight from
http://www.na.fs.fed.us/pubs/silvics_manual/Volume_1/larix/laricina.htm
 
 Growth rate (particularly diameter) declines after 12 to 15 years if tamarack is planted at close spacings such as 1.5 by 1.5 m (5 by 5 ft), but it should be unimpeded for the first 25 years at wider spacings up to 2.4 by 2.4 m (8 by 8 ft). In a good plantation in eastern Ontario, height at 25 years averaged 14.9 m (49 ft), d.b.h. 17.3 cm (6.8 in), and volume 202 m³/ha (32 cords/acre). Depending on site, final harvests of 189 to 252 m³/ha (30 to 40 cords/acre) are possible at 25 years in well-managed tamarack plantations (27). Intensively cultured plantations can produce two to three times more biomass than conventionally tended stands (51).

[ihookem]

I wanted to plant trees for my future firewood supply and ended up with hybrid poplars. They have been growing 3 summers now. I went with hybrid poplars for a few reasons, it grows fast(not as fast as they  said but fast)  they are real nice lookng trees, I got the "cuttings for 15 cents each, I can most likely sell the twigs or cuttings for some money,  it grows very straight planted close together and splits easy and when I cut them down you end up with sucker shoots from the trunk. The down side is of coarse it lacks the btu's of maple and it does not do well with weeds or grass. They love tons of water too. I planted mine on high ground and they only grew an avr. of 2 ft. per year. We have had three dry years in a row to make matters worse. If taken care of they will grow 4' the 1st yr. and 5' the 2nd year and about 6 ft per year after that. They also grow quite tall when close together. I have about 350 on 1/3 of an acre with ash, maple and some elm growing with them and another 1/2 acre growing naturally with ash, hickory, elm,and white pine for good looks. I did this cause I've always said "someday opec is gunna turn off the spicket" and at least I have poplar to burn. I figure in 7 years I can thin them some and hope to get  a cord or so. Then let the best sucker shoot grow, and the ash, cut the other sucker shoots into cuttings and sell them or replant or just let them all grow.  If I had to do it all over I think I would have tried finding elm trees, but have no idea where to find them. Silver maple might have been better too.

[woodtroll]

That leads back to Black Locust. It grows well in moist and dry conditions. Grows straight, sprouts from stump, likely could plant cuttings, splits well, burns very hot. May be a nitrogen fixer. Some of these good traits are the same as why it can be a weed.

[Magicman]

Back in the "wood stove days", my Dad told me that the only wood that they used was Black Locust.

[Phorester]

WOODTROLL, black locust is a legume so it indeed fixes nitrogen in the soil.  In the South decades ago before lawn fertlizers were common, black locust was  planted as a yard tree because the nitrogen fixing qualities of its roots made the grass greener in the yard.

[SwampDonkey]

Just plant alders, it's been known to warp a stove and fixes nitrogen to.

[Twig farmer]

Apple. Grows pretty fast, produces fruit, gives great heat.

[SwampDonkey]

 

I'm not in the apple wood camp like some folks. I tried some one winter as I cleared out an old orchard. All I can tell ya's is I was some glad to get into the hard maple pile to keep my arse warm.

[Twig farmer]

I'm not in the apple wood camp like some folks. I tried some one winter as I cleared out an old orchard. All I can tell ya's is I was some glad to get into the hard maple pile to keep my arse warm.

This link says Apple has more BTUs per cord than Maple..if "other" is hard maple..silver can't even compare...

http://extension.usu.edu/forestry/HomeTown/General_HeatingWithWood.htm

Personally, I found the white oak to be just as the link said. It does the best job. I had about 3 cord of it this year, and next I'll have 6.

[SwampDonkey]

I don't believe it from my experience with it. Apple wood I mean. In fact they don't even have the right weight per cord for hard maple. A cord is 100 ft³ of solid wood on average, which is 5600 lbs green, 4400 lbs @12%. Any apple wood I've handled would compare between black ash and red maple, which matches their figures pretty much bang on. Their white ash is way off to.

[downeast]

By far one of the most interesting threads in any forum ! 

The "best" species does depend on soil quality, Ph, micro climate, and again, the density/BTU of the species. Also, as said, the "pioneer" growth of any tree, or how fast it will grow to harvestable size for firewood after a harvest.  These downeast Maine coastal woodlands are in bad shape due to lack of proper forestry since WWII. The iconic Maine 'look' of spruce/fir is only because of neglect, associated disease, and the so-called environmentalist Bambi attitude towards ANY cutting, sustainable or not. Forestry be damned.

What do we have here for firewood ? In the Deer Isle/Blue Hill penninsula mostly Red/Soft Maple, Paper/White Birch for firewood, and a scattering of Red Oak, Green Ash, small Beech (diseased > 12" DBH ), some Yellow Locust, little White Ash, a lot of abandoned Apples. Most of our 5-7 cords/year is White Birch and Red Maple.

Thanks for an informative, intelligent thread guys. 

[woodtroll]

Osage orange easy to split? Never in my experience. Of course compared to straight ash or white oak for splitting...

[SwampDonkey]

Same with the birch, and it can't be yellow birch they have there, it's weight is way off. White birch is easy to split even air dried, yellow is medium though. Just the weight of the axe will practically bust white apart. Their figures on weight are about 1000 lbs off on hardwood like beech, hard maple, and yellow birch.  White ash, beech, yellow birch, hard maple are all right there together as far as density. Not a lot different in 12 % dry weight either, right around 4400 lbs average. And most folks will have their firewood around 16-20%, so it's even heavier.

[downeast]

Same with the birch, and it can't be yellow birch they have there, it's weight is way off. White birch is easy to split even air dried,

Wish it were so "easy".  Paper/White Birch in many cases is a $#%&* to split, dry or green. Depends on the growth- whether it heliotropes ( follows the sun, or grows as a pioneer in the open for straight grain growth). Paper Birch "pooches" or rots quickly if not split along the bark. We usually score the bark before bucking. It rots fast unfortunately in spite of bark splitting, so it's a bad storer for firewood. A year at most, then it starts to do the carbon thing====ashes to ashes.

[SwampDonkey]

You sure your not into that cursed gray birch being down east an all? My uncle split cords and cords and I helped in my younger years, and it was a joy. I don't use any here just yellow birch. But, as to it's spoiling that can be true, but we never left his wood outside to spoil, it went under cover before the warm season. There were cords and cords of white birch laying to waste on crown lands, 18-24" blocks of it. We used to load (grandfather and I) the half ton full after returning from fishing trips.

[downeast]

You sure your not into that cursed gray birch being down east an all? My uncle split cords and cords and I helped in my younger years, and it was a joy. I don't use any here just yellow birch. But, as to it's spoiling that can be true, but we never left his wood outside to spoil, it went under cover before the warm season. There were cords and cords of white birch laying to waste on crown lands, 18-24" blocks of it. We used to load (grandfather and I) the half ton full after returning from fishing trips.

No, it's Paper Birch, common pioneer species here that gets crowded by spruce and fir. It rots fast even under cover and scored in a year, maybe two at most.
Yellow Birch isn't common here, though it ranks up with the oaks for BTUs. You are spoil't. 
BTW: what are "crown lands" ? Something the Queen owns ?

[SwampDonkey]

what are "crown lands" ? Something the Queen owns ?

like that.

Well if I didn't know better I'd say the forest companies owned them. But, no they are suppose to be public owned land like your state forests.

Yellow birch isn't my main firewood, hard maple is. But, yellow birch and beech in lesser quantities. Getting hard to get good beech, it's half dead and rotten.

Gray birch has waxy triangle leaves with a solitary male catkin on worty branch tips. Just in case.

[jim king]

Physical properties of burning wood fire wood BTUs


Physical Properties of Firewood by Tree Species
Chart of Common Firewood Heating Potential
By Steve Nix, About.com Guide
See More About:
•   firewood
•   best firewood trees
•   firewood fuel value
Firewood performance can differ from species to species. The type of tree you use for burning can vary widely in heat content, burning characteristics, and overall quality. I have created a table that presents several important burning characteristics for most species used in North America.
Definitions of Chart Terms
•   Density - wood's dry weight per volume. Denser or heavier wood contains more heat per volume.
•   Green Weight - the weight in pounds of a cord of freshly cut wood before drying.
•   mmBTUs - million British Thermal Units. Wood's actual available heat measured in BTUs.
•   Coaling - wood that forms long-lasting coals are good to use in wood stoves because they allow a fire to be carried overnight effectively.
Wood Heating Values
Common Name   Density-lbs/cu.ft.   Pounds/cd. (green)   Million BTUs/cd.   Coaling
Hickory                50   4,327   27.7   good
Osage-orange   50   5,120   32.9   excellent
Black locust   44   4,616   27.9   excellent
White oak   44   5,573   29.1   excellent
Red oak   4                        4,888   27.4   excellent
White ash   40   3,952   24.2   good
Sugar maple   42   4,685   25.5   excellent
Elm                35   4,456   20.0   excellent
Beech                41      27.5   excellent
Yellow birch   42   4,312   20.8   good
Black walnut   35   4,584   22.2   good
Sycamore   34   5,096   19.5   good
Silver maple   32   3,904   19.0   excellent
Hemlock   27      19.3   poor
Cherry                33   3,696   20.4   excellent
Cottonwood   27   4,640   15.8   good
Willow                35   4,320   17.6   poor
Aspen      18.2                             good
Basswood                4,404   13.8   poor
White pine   23      15.9   poor
Ponderosa Pine      3600   16.2   fair
Eastern Red Ced  31   2,950   18.2   poor
Sponsored Links
Physical properties of burning wood fire wood BTUs


Physical Properties of Firewood by Tree Species
Chart of Common Firewood Heating Potential
By Steve Nix, About.com Guide
See More About:
•   firewood
•   best firewood trees
•   firewood fuel value
Firewood performance can differ from species to species. The type of tree you use for burning can vary widely in heat content, burning characteristics, and overall quality. I have created a table that presents several important burning characteristics for most species used in North America.
Definitions of Chart Terms
•   Density - wood's dry weight per volume. Denser or heavier wood contains more heat per volume.
•   Green Weight - the weight in pounds of a cord of freshly cut wood before drying.
•   mmBTUs - million British Thermal Units. Wood's actual available heat measured in BTUs.
•   Coaling - wood that forms long-lasting coals are good to use in wood stoves because they allow a fire to be carried overnight effectively.
Wood Heating Values
Common Name   Density-lbs/cu.ft.   Pounds/cd. (green)   Million BTUs/cd.   Coaling
Hickory                50   4,327   27.7   good
Osage-orange   50   5,120   32.9   excellent
Black locust   44   4,616   27.9   excellent
White oak   44   5,573   29.1   excellent
Red oak   41                4,888   24.6   excellent
White ash   40   3,952   24.2   good
Sugar maple   42   4,685   25.5   excellent
Elm                35   4,456   20.0   excellent
Beech                41      27.5   excellent
Yellow birch   42   4,312   20.8   good
Black walnut   35   4,584   22.2   good
Sycamore   34   5,096   19.5   good
Silver maple   32   3,904   19.0   excellent
Hemlock   27      19.3   poor
Cherry                33   3,696   20.4   excellent
Cottonwood   27   4,640   15.8   good
Willow                35   4,320   17.6   poor
Aspen   


   18.2   good

[SwampDonkey]

Now I see where the figures are based on: "Weight and Heat content figures are based on seasoned wood at 20% moisture content, and 85 cu ft of wood per cord."

No wonder I can't believe them, the cordage of solid green wood is way too low. Split firewood stacks a lot tighter than round wood. I know it to be true because of thousands of scale slips processed by marketing boards from mills. Always been 2.5 metric tonne in hardwood which is averaged 5600 lbs green (beech, maple, yellow birch) with 100 ft³ of solid wood.

[downeast]

Boy, Steve Nix's chart missed some species: White/Paper Birch, and Red/Soft Maple. Fast pioneer growers here Downeast Maine. 

That 20% moisture content is interesting...just "interesting" maybe academically. We don't have the time, interest, or luxury to run around checking moisture in firewood. Those M²(moisture meter) things only check the surface anyways. Good for milling.

We heat 100% with wood ( well, 99% with a propane space heater for those winter days away) with  two EPA wood stoves.  For too too long the trees are cut in winter ( no bugs, hard ground, soft landing in snow, easier bucking over snow, no water under foot, less sweat ), stacked crudely in the open in butt stove length, then split and stored later in the summer and early fall. It has worked well for years even with the- rare for us - dreaded Red Oak. The secret ?  Stack the +/- 18" butts in rows separated by a foot or so. They dry some in winter and spring.  After splitting and stacked in the wood shed they are ready by November.

[SwampDonkey]

Most well seasoned firewood is going to be 16-20%. You have to have a baseline, in this case 20 % and not green, because trees between species can have moisture content of 30 - 267% of their weight.

For academic purposes the Wood Handbook uses a formula to figure the Max moisture content of a species based on specific gravity of green wood and wood cell walls. Maximum moisture content Mmax for any specific gravity can be calculated from Mmax=100(1.54-G_g)/1.54G_g where G_g is basic specific gravity (based on ovendry weight and green volume) and 1.54 is specific gravity of wood cell walls. Maximum possible moisture content varies from 267% at specific gravity of 0.30 to 44% at specific gravity 0.90.

Conceptually, the moisture content at which only the cell walls are completely saturated (all bound water) but no water exists in cell lumens is called the fiber saturation point.The fiber saturation point of wood averages about 30% moisture content, but in individual species and individual pieces of wood it can vary by several percentage points from that value. The fiber saturation point also is often considered as that moisture content below which the physical and mechanical properties of wood begin to change as a function of moisture content.

From what I can gather green weight for each species listed in the Wood Handbook is taken at MC 30%. That is the baseline used for the FSP of wood. At or above this MC wood is considered green. Of course this varies from sample to sample in a species and across species. But you have to have a baseline of some kind. Without having the "Standard Method of Testing Small Clear Specimens of Timber"  from the American Society for Testing and Materials, I can only make that assumption.

[stonebroke]

What species has 265% moisture?

Stonebroke

[SwampDonkey]

I think that would be the extreme and probably rare.

Some tabulated MC of sapwood are listed in the Handbook, and heartwood are listed as well, based on averages I assume.

Western red cedar 249%
sugar pine 219 %
basswood 133 %
cottonwood 146%

MC% is based on weights when oven dry. Heartwood moisture content can be almost the same in some species or as much as 5 times less in others.

The data quoted by Jim above is all out of whack because one column is talking about wood at 12 % MC (look it up in the Wood Handbook if you want to see), the next is talking about green wood at 30 % MC, possibly higher, followed by BTU's based on a cord shorted of volume and at 20 % MC. And no clue of methodology until you Google around and find the same data being used by someone else willing to explain it.

[SwampDonkey]

"Switch grass is more like 6 tons/ac per year from what I have learned.  I guess that it depends on the quality of the site.
"

Auburn study.  http://bioenergy.ornl.gov/papers/misc/switgrs.html  They even said they got 15 tons/acre the one year.

What about fertilizer input costs and would you eventually have to fertilize those poplar sites? With the grass it would be an annual harvest verses 5-10 years apart for the poplar. So you would need more acreage of the poplar to have a continuous stream of wood at different stages of growth.  Around here there is so much poplar through the country that you wouldn't have to worry about cutting the same ground for decades. Enough time to rebuild the soil between harvests? Never seen anything grow any faster than largetooth on a good site. 8" DBH in 13 years.

[downeast]

Whew Msr. Swamp, you mean to say that the moisture content can be > the weight of the wood ?  As a fellow "bright one" ( graduate degrees, pro experience in and out of academia and mil ) I have got a bridge to sell you.  No offense SwampD, butt, some things are not the duck Groucho. As in: "if it looks like a duck, sounds like a duck, s&%$s like a duck,......."
Hey, we now cut the firewood this winter, split and stack for next. Period. It is the duck.

JMNSHO

[SwampDonkey]

Quack, Quack!

[downeast]

Quack, Quack!

 

[WDH]

If you take a block of wood and perfectly squeezed all the water out of it so that the wood had 0% moisture, and if you captured that water that you squeezed out, you could then weigh the dry block of wood and you could weigh the water.  In some species, the water removed from the wood weighs more than the dry block of wood it was removed from.  So, if you divide the weight of the water by the weight of the dry wood (that is how M% is calculated) then the moisture content will be greater than 100%.

If the wood and water weighed exactly the same, say 50 pounds of dry wood and 50 pounds of water, then the M% would be 100%, or 50 divided by 50 x 100.   

[downeast]

If you take a block of wood and perfectly squeezed all the water out of it so that the wood had 0% moisture, and if you captured that water that you squeezed out, you could then weigh the dry block of wood and you could weigh the water.  In some species, the water removed from the wood weighs more than the dry block of wood it was removed from.  So, if you divide the weight of the water by the weight of the dry wood (that is how M% is calculated) then the moisture content will be greater than 100%.

If the wood and water weighed exactly the same, say 50 pounds of dry wood and 50 pounds of water, then the M% would be 100%, or 50 divided by 50 x 100.   

I still have a bridge to sell you.    50 / 50 x 100 = ____. We never learn't that far. 
You're talking theoretically about a closed system experiment. Now, truth telling time: have you done this with that block of wood in a closed system ? Real world, real time. Results ? M% =
There are statistics, and there are .........................

[beenthere]

 

What ya sayin?

[Ianab]

Bit of confusion here 

% moisture content is measured by comparing the DRY weight of a piece of wood, with it's current weight. And thats done by drying it in an oven untill ALL the water is driven out.

So say you had a piece of wood weighing 1lb, you oven dry it untill it's totally dry and it weighs 1/2 lb.

That means it had 1/2 lb of water, and 1/2 lb of wood, the ratio is 100%.

It is not exactly the same as we measure percentages in other stuff, but it's how moisture in wood is measured. Don't ask me why, but I suspect it's to make the maths easier as it's measured from DRY, not from some random wet measurement.

Re the Wood regaining moisture, yes it does, real world. I've tested green blocks of wood by microwaving them untill they got no lighter. 0% moisture. Then you leave it out on the bench for a week, and it re-gained some of the weight, about 12% eventually.

You can test this youself if you want. 

Ian

[downeast]

Bit of confusion here 
% moisture content is measured by comparing the DRY weight of a piece of wood, with it's current weight. And thats done by drying it in an oven untill ALL the water is driven out.
So say you had a piece of wood weighing 1lb, you oven dry it untill it's totally dry and it weighs 1/2 lb.
That means it had 1/2 lb of water, and 1/2 lb of wood, the ratio is 100%.
It is not exactly the same as we measure percentages in other stuff, but it's how moisture in wood is measured. Don't ask me why, but I suspect it's to make the maths easier as it's measured from DRY, not from some random wet measurement.
Re the Wood regaining moisture, yes it does, real world. I've tested green blocks of wood by microwaving them untill they got no lighter. 0% moisture. Then you leave it out on the bench for a week, and it re-gained some of the weight, about 12% eventually.
You can test this youself if you want. 
Ian

Sorry Ian et. al, We're back to Groucho's duck.
If you measure a body's % of moisture it is the %. Period. That's what we Call Scientific Method. Ain't no other valid measurement.    That is what a Closed System will measure. It's controlled, repeatable, accepted. Now, if you want to make another kind of measure, fine, like 200% moisture content !!!??!? . But it's not science or real.
It's kind of like the arguments over what a cord is. Rick, face, banana cord, volume, mass, air space, round logs, tighly packed splits, lamb chops, Dodge Ram pickup bed cord. Everyone knows. 

BTW Ian: why does NZ policy mandate plantation reforestation. Single species, in neat rows on the hills. It is strange to see this lack of diversity and 'order'  for a healthy regen.

[beenthere]

de  Care to elaborate more on what it is you are hinting at?

[WDH]

Now, truth telling time: have you done this with that block of wood in a closed system ? Real world, real time.

Yes.

[Ianab]

That is what a Closed System will measure. It's controlled, repeatable, accepted. Now, if you want to make another kind of measure, fine, like 200% moisture content !!!??!? . But it's not science or real.

The science is the same, it's just what are you comparing? It's just a ratio, expressed as a percentage.
It's the amount of water compared with the amount of DRY wood. The amount of dry wood is a fixed value, the weight of green wood is a variable. Imagine trying to do the maths on drying rates if you were working from percentages of the current moisture content, which is a moving number.

It may be more correct mathematically, but in a practical sense it's a nightmare.

BTW Ian: why does NZ policy mandate plantation reforestation. Single species, in neat rows on the hills. It is strange to see this lack of diversity and 'order'  for a healthy regen.

Simple economics. 99% of the timber production in NZ is introduced plantation forest. Pine, Douglas fir or Euclayptus grown on a 20-50 year rotation. It's planted and harvested as a crop, just like corn or beans, just a little longer between planting and harvesting.  None of your timber speces are endemic to NZ, and the native species are very slow growing with a complex succession process through several stages of forest growth. Might be 50-100 years before the desireable crop trees are even established, and maybe 300+ years for them to mature. A forest giant might be 800+ year old.

So you have 2 types of forest, commercial plantation, mostly pine, which is intensly managed and harverested. And native forest, which is only a fraction of the original pre-human amount and is mostly preserved in parks and reserve land. Either untouched or slowly regenerating.

There is some limited harvesting of native timber from private land, but it's strictly controlled and the annual timber supply is very small.

Ian

[SwampDonkey]

downeast, the methods for measuring wood MC is tried and true. Been done longer than you and me have been on this planet. There is also two kinds of water in wood, bound water and free water. Free water effects weight only and bound water affects, weight, specific gravity, volume and other physical properties of wood. The threshold where volume and physical properties of wood change is the fibre saturation point, which can't really be pinned to one exact MC%, but academically they use 30 % MC as a point of reference. Hard maple, beech, yellow birch and eastern spruce and fir are very close to that figure. You need to know these things when making paper because water doesn't make you money, only wood fibre. It's like trying to make bread and thinking the amount of water doesn't matter, there is a recipe. 

Wood moisture is measured that way because physical properties continuously change from green condition until every bit of moisture is removed (oven dried). Don't confuse air dried seasoned wood for oven dried. Seasoned wood varies by climate and reaches equilibrium with the surrounding air, they call it the Equilibrium Moisture Content. Why you suppose they set your flooring lumber in your living room for a week or two? To get the wood to equalize with the climate in that room.

If you can't grasp that then relative humidity is really going to jam those wheel cogs.

[downeast]

downeast, the methods for measuring wood MC is tried and true. Been done longer than you and me have been on this planet. There is also two kinds of water in wood, bound water and free water. Free water effects weight only and bound water affects, weight, specific gravity, volume and other physical properties of wood. The threshold where volume and physical properties of wood change is the fibre saturation point, which can't really be pinned to one exact MC%, but academically they use 30 % MC as a point of reference. Hard maple, beech, yellow birch and eastern spruce and fir are very close to that figure. You need to know these things when making paper because water doesn't make you money, only wood fibre. It's like trying to make bread and thinking the amount of water doesn't matter, there is a recipe. 

Wood moisture is measured that way because physical properties continuously change from green condition until every bit of moisture is removed (oven dried). Don't confuse air dried seasoned wood for oven dried. Seasoned wood varies by climate and reaches equilibrium with the surrounding air, they call it the Equilibrium Moisture Content. Why you suppose they set your flooring lumber in your living room for a week or two? To get the wood to equalize with the climate in that room.

If you can't grasp that then relative humidity is really going to jam those wheel cogs.

There are times when too much info is overload. The grey matter is jammed......How'd ya know ?

[WDH]

This is when you turn the thread to food  .

[Magicman]

Danny, I'm gonna have to feed you real soon.....

[WDH]

Success  .

[ihookem]

I got a bunch of Black locust today. If you can get it to grow fast it might be worth planting if you can get seedlings cheap. It was very heavy wood but also holds a lot of moisture. The Ash was much lighter but drier.