[Strawbale] Sustainability of wood heat.

[Corwyn]

On Feb 10, 2008, at 18:43, Sherwood Botsford wrote:

> Corwyn wrote:
>> On Jan 31, 2008, at 01:02, Sherwood Botsford wrote:
> 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.

No, I am saying that if you are creating pollution, and you don't know 
how, or how quickly, it is being rendered into non-pollution, that you 
must assume it is just accumulating.  Thus the relevant metric is not 
concentration but total produced.

>> 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.

But the 24" tree is adding 2.3 inches^2 time height where the 6" is 
only adding 1.9 inches^2 times height.  So, using your numbers, the 24" 
tree is an increase over the 6" tree, not a diminishing return.  More 
if you assume it is taller.

But, that was not my point.  What you have shown is how much wood you 
can take at its current production rate, but haven't shown how that 
will or will not change that production rate.

> 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.

Seems to me like an upper bound, if you are removing 100% of the total 
biomass increase.  The forest needs some percentage of that biomass to 
survive.  Neither you, nor I, nor possibly anyone, knows what that 
percentage is.  If you assume it is zero, I think you are dooming the 
forest, in the same way that those who think it is negative are, just 
slower.

> 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.

Right.  You grow them bigger there.

>> 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?

Around 1600.

And more than weatherstripping, insulation.

> True.  We do the best we can.  Keep on learning.  How do we define 
> sustainable?  Forever?

Forever.  Yes, please.  Ok, fine, 5 billion years.

>  Nothing is sustainable.

Sure it is.  This planet had a positive energy balance for its first 
4.5 billion years.  Storing energy capital, even.  We are burning 
through that capital at a rate of a million years accumulation per 
year.  Unsustainable doesn't begin to describe it.  But if 'dumb 
animals' (and dumb humans) could do it, smart humans should have no 
trouble, right?

And really, it's not like we have a choice.  Those living on this 
planet can operate it sustainably, or they can die as a species.

Thank You Kindly,

Corwyn



-- 
Corwyn
Kermit didn't know the half of it...
http://www.greenfret.com/
corwyn at greenfret.com