[Strawbale] Sustainability of wood heat.

[Sherwood Botsford]

Corwyn wrote:
>
> On Jan 31, 2008, at 01:02, Sherwood Botsford wrote:
>
>>
>> Particulates depend on how well you run the stove.  Poison and pollution
>> are matters of concentration.  I have 12 neighbors within a 4 mile
>> radius.  That's 1 neighbor per 900 acres roughly.
>
> True, but until you provide the mechanism for them to convert to 
> something else, you get to sum over the entire planet.  Thus, you have 
> 7 billion 'neighbors'.  Note, I am not saying there isn't one, just 
> that if you don't know what it is, you have to assume their isn't one, 
> and that poisons and pollution are accumulating and becoming more 
> concentrated.
>
Hmm.  I think there is a core assumption we don't agree on.  I think you 
are saying

If a solution isn't universally adoptable, it can't be used.

Where I'm saying,

A solution that works for a small group is a workable partial solution.

Example:  I've build my school's entire computer network from industrial 
castoffs.  It works for us.
By it's nature however, it depends of there being usable machines 
destined for the dump. So it is not a universally applicable solution.  
My use of wood decreases the total fossil fuels used.  It requires open 
land and some wind to use.
>
>> Here's how I figured it:  By looking at stumps the mature black poplar
>> on my land are between 80 and 120 years old when they start to die off.
>> Often the time after age about 60 is pretty slow growth.  Ok.  We'll
>> assume 100 years for a mature tree.   On that basis I can harvest about
>> 1% of the tree biomass per year.  This ignores the much faster growth
>> while young, the biomass in the understory.  With much thought and
>> study, I could remove 3-4% of the biomass per year.
>
> I am not sure what you are saying here.  How do you get from how long 
> one (short-lived) trees last, to how much you can sustainably harvest?

It's an oversimplification.  If a tree lives 100 years, then falls over 
dead, then on the average that tree grew 1% of it's biomass every year.  
It's not that simple.  Firstly for every tree that makes it to 100 years 
there are many that die on the way.  Even on a biomass/square foot 
basis, the fixed biomass in a year starts small, (because a small tree 
increasing it's mass by 10% is still a small amount of mass) and 
increases exponentially until the tree is about 2/3 of it's mature 
size.  At that point you get diminishing returns, often due to the 
energy requirements to move water to the top of the tree, and 
competition for light.  You can see this in the growth ring patterns.  A 
6" poplar here will grow about 1/5 of an inch diameter per year.  By the 
time is 24" that will taper off to 1/16" per year.  The same area that 
grows 1 24" poplar will grow 10-20 6" poplar

While the 1 /(average lifespan) is an oversimplification it's a lower 
bound.  I probably could harvest 2-3% of the tree biomass on a 
sustainable basis, but the closer I get to the total productivity, the 
more careful I have to be to not screw up how I take that mass out of 
the system.  Short rotation poplar farms can harvest a crop every 8 
years.  But to do that, you have to grow it as a mono-culture, kill all 
the weeds under the canopy, and add supplemental fertilizer.  In the 
long run, I think this mines the soil.

A similar situation at a faster scale is harvesting hay.  You can cut a 
hay crop off a pasture every year indefinately if you return the manure 
back to the field.   With a hay crop, you are harvesting close to 50% of 
the gross productivity. (You're taking most of the top, but are leaving 
the roots.)

Definition:  Gross productivity.  Number of tons/year of carbon fixed as 
carbohydrates (cellulose, lignan, sugars)  Includes increase in 
branches, leaves, roots.  It's a measure of how efficient a plant 
community is at converting sunlight.

Net productivity:  Total productivity - Decomposition.  Decomposition 
includes munching by bacteria, insects, fungi, and animals. 


Generally in a climax ecosystem there is no net productivity.  Trees 
die.  They rot. Get eaten.  Leaves fall. Become slug and worm food.  
(The only exception I know of are spagnum peat bogs.  They just keep 
sucking up the CO2 and piling it deeper and deeper.  Presumably the 
carboniferous forests that made our current coal seams and much of our 
oil were similar.)

What I'm doing is replacing some of the decomposers.  If I replace all 
of the decomposers, the ecology is severely distorted. If I take  tiny 
amount, the distortion is unmeasurable. 

As you harvest more material, the community is moved away from the 
climax balance point.  Total productivity remains the same, Net 
productivity increases.

>
> If you are getting a cord out of two trees, I am impressed.  I 
> seriously doubt those are 100 year old trees though, unless they grow 
> them bigger there.   It takes me at least 10 trees to make a cord.
>
A mature poplar is 18" - 24" at the stump, 60-80 feet tall.
It's still a foot at the start of the crown.  Average 70 feet.  Volume 
of a frustrum (cone with it's tip cut off)
V = 1/3 (B -b) H  wehre B is the area oft he base, and b is the area of 
the top.

V = 1/3 (pi*1^2 - pi * 0.5^2) 70
V = 1/3 pi (1-1/4) 70
V =  ~55 cubic feet.
Add in a few of the larger branches, adding that stacked wood is 1/3 
air, I think 2 trees per cord is a good estimate.
(1 cord = 4 x 4 x 8 = 128 cubic feet.)

Definition:  Gross productivity.  Number of tons/year of carbon fixed as 
carbohydrates (cellulose, lignan, sugars)  Includes increase in 
branches, leaves, roots.  It's a measure of how efficient a plant 
community is at converting sunlight.

Net productivity:  Total productivity - Decomposition.  Decomposition 
includes munching by bacteria, insects, fungi, and animals. 


Generally in a climax ecosystem there is no net productivity.  Trees 
die.  They rot. Get eaten.  Leaves fall. Become slug and worm food. 

What I'm doing is replacing some of the decomposers.  If I replace all 
of the decomposers, the ecology is severely distorted. If I take  tiny 
amount, the distortion is unmeasurable. 

>
> Tens cords is a lot.  I burn 2 for a 7500 Degree day climate.
>
Now I'm impressed.  Gives me incentive to put in more weatherstripping.  
How many square feet is your house not including basement?
>> My woodlot is about 12 acres.  So I have to cut not quite two trees per
>> acre on the average to get 10 cords. Or ten 8" poplar per acre.   At 10
>> foot spacing there are over 400 trees per acre.  (And yes 10 is more
>> than 1% of 400, but it was 1% of all age classes.  I usually end up with
>> a mix of sizes.)
>
> You are getting 1.5 cord trees every 10 feet!?  All I can say is wow.
>
No.  An 8" poplar is 0.1 cord  A 24" poplar is 0.5 cord.  The total wood 
on the land is about 30-50 cords per acre.
>> As a mark of our success:  Our pair of piliated wood peckers have
>> successfully raised a brood each year. (5 of them on the platform feeder
>> at once!)  Both kinds of nuthatches fledged their flocks, and the downy
>> and hairy also succeeded.
>
> I am not sure how conclusive that is.  I suspect that the piliated at 
> least is using more than your 12 acres.  Mine is doing well as well, 
> and he just had 50 acres clear cut in his territory.
>
Conclusive, no.  Wildland ecology has few conclusions. As a measure 
yes.  Others around me also have trees.  But if I was sufficiently 
destructive of good woodpecker trees, then my land would not have 
nesting woodpeckers. They'd go to where the picking (pecking?) was easier.
>> My conclusion:  Do I have an impact? In the long term, yes.  Is it
>> sustainable?  In the long term, yes.
>
> Maybe.  I am not sure anyone knows what it would require to be 
> sustainable.  We do what we can, then we do more, and we hope.
>
True.  We do the best we can.  Keep on learning.  How do we define 
sustainable?  Forever?  Nothing is sustainable.
If I have to make a definition, I'd say 10 times the top quartile pool 
residence time of carbon    So for a pasture, where the long term (top 
quartile) carbon pool of heavy stems and major roots is 2-3 years, I'll 
grant you sustainable when you can do 20 years.  For my forest, 200-300 
years.  For coastal temperate rain forest? Probably 1-2 thousand years. 
Amazon rain forest, probably 2
>>  Do I have much of an alternative in this climate?  Not really.
>
> Sure.  Get that 10 cord number down to 3. or better.
>
Working on it.  As I mentioned, I'm probably going to come in between 6 
and 7 this year.  (Remember that I cook on this too.) 
>
> I want to emphasize that I think you are doing well, just that I don't 
> think anyone can think we are done yet.
>
> Thank You Kindly,
>
> Corwyn
>