[jon]

jon  asked the Naked Scientists:
   
Everyone seems very excited about having trees suck carbon out of the atmosphere.  While this is a great thing for a few years, if you take the longer view, what happens when the trees die?  I know from experience that picking up year-old fire wood is much more difficult than 5-year-old fire wood: bacteria slowly digest the wood, until it is nothing more than a shell.

When the "experts" advocate planting of trees, do they really have a solid long-term plan in mind?

Jon

What do you think?

[Geezer]

It's true that a single tree is only a temporary carbon sink. When the tree decomposes or is burned, the carbon is released back into the atmosphere. However, an area of land that is maintained as a forest is an indefinite carbon sink.

[CliffordK]

I agree that the tree is part of a carbon cycle of growth & absorption of carbon, death and release of carbon, and regrowth.

There are, of course, many tons of carbon locked up in the forests around the world.

Some theories indicate that the great rainforests of the world (Congo and Amazon) are net carbon sinks, perhaps as future sources of oil and coal.

Also, if the tree is converted into durable goods (books, houses, furniture, etc), it may last for quite some time, although many items will eventually end up in the landfill.

[imatfaal]

Old wood is not necessarily decayed wood.  I can look out of my window and see wood that was last alive and growing over 300 years ago (original windows and doors of a row of buildings built in 1690).  Thats a pretty damn good carbon storage.

Hard deciduous wood really doesnt decay in a few years - my compost heap, which is a very decay friendly environment, has been kept on the straight and narrow for a good 15 years with chunks of hardwood driven into the ground.

[Geezer]

I can look out of my window and see wood that was last alive and growing over 300 years ago

That's nuthin. I'm looking out my window at wood that's still growing after 100 years  []

(Some of the Ponderosa Pines might actually be quite a bit older, but I think the Douglas Firs are pretty mature at around 75 years.)

[Airthumbs]

The tree by the name of Prometheus, felled in 1964, was at its demise 4862yrs old! That would have made it about as old as some of the pyramids! Here is a pretty good list of ancient trees.  http://en.wikipedia.org/wiki/List_of_oldest_trees

Ye olde trees  []

[Geezer]

BTW, it's not just hard woods that last a long time. I did some remodelling on a house in the Phoenix area in Arizona. The internal walls were typical drywall on 2" X 4" wood framing, probably fir of some sort or another.

The old wood framing was so dry it was virtually impossible to drive a nail into it without splitting it. It was like concrete! The only way to attach anything to it was to insert screws after drilling substantial pilot holes.

[CliffordK]

I wonder what the average lifespan for furniture and houses would be.

I've seen lots of 50 to 100 year old houses that have been bulldozed, shredded, burnt, or taken to the dump.  Nothing is forever, especially as people seek bigger and better.

[jon_bondy]

"an area of land that is maintained as a forest is an indefinite carbon sink."  I don't see how this could be so.  Trees grow and eventually die, fall down, and are consumed by bacteria on the ground.  I know this because firewood that is stored for too long becomes very light and release very little heat: it has already been digested. Trees make great temporary storage containers for carbon, but after 50 to 200 years, the carbon is released.

[Geezer]

"an area of land that is maintained as a forest is an indefinite carbon sink."  I don't see how this could be so.  Trees grow and eventually die, fall down, and are consumed by bacteria on the ground.  I know this because firewood that is stored for too long becomes very light and release very little heat: it has already been digested. Trees make great temporary storage containers for carbon, but after 50 to 200 years, the carbon is released.

In a forest, new trees grow to replace the ones that die. If all the trees die or are chopped down, it's no longer a forest.

[Bored chemist]

"I know this because firewood that is stored for too long becomes very light and release very little heat: it has already been digested. "
http://xkcd.com/285/

[Don_1]

I wonder what the average lifespan for furniture and houses would be.

I've seen lots of 50 to 100 year old houses that have been bulldozed, shredded, burnt, or taken to the dump.  Nothing is forever, especially as people seek bigger and better.

I walked into a pub in a rather rough part of town which had sawdust scattered on the floor and remarked to the barmaid how unusual it is to see this in a pub these days.

"Sawdust!" She exclaimed, "That's not sawdust, that's last night's furniture!"

Trees may be a short term storage of carbon, even those real oldies which Airthumbs pointed out are short term compared to the Earths age, but they are only short term as individuals. As one of many in a forest where they are replaced by new growth, they are long term. So long as we don't keep chopping down forests.

[CliffordK]

So long as we don't keep chopping down forests.

If you regrow forests where you chopped down the forest, it becomes part of a carbon cycle, just like a field growing vegetable oil for fuel use.  One would theoretically reach a steady state of the amount of sequestered carbon in the trees.

Optimally, however, one could slowly increase the amount of carbon being captured by trees and plants.  But, there isn't a practical way to bury trees to make the next generation's coal.  And, I find it doubtful that anybody will start digging coal out of mines, and then refilling them with plant matter.

[Don_1]

So long as we don't keep chopping down forests.

If you regrow forests where you chopped down the forest, it becomes part of a carbon cycle, just like a field growing vegetable oil for fuel use.  One would theoretically reach a steady state of the amount of sequestered carbon in the trees.

Sorry, yes I should have qualified that;

.....So long as we don't keep chopping down forests and not replanting.

[marcelo]

Besides reaching a steady state of carbon fixed in wood, I recently read about the idea of simply burying the trees after you chop them. If they're deep enough there won't be soil and hence no rotting happens that could generate CO2 (although as already discussed, certain wood can be quite resistant to injuries of any kind)


newbielink:http://www.science.org.au/nova/newscientist/108ns_006.htm [nonactive]


A variation of the burial theme has been proposed in which you burn the logs til they;re charcoal so to lock the co2....here it's an article.

newbielink:http://www.guardian.co.uk/environment/2009/mar/13/charcoal-carbon [nonactive] 

[CliffordK]

If the plan is to bury the trees.
You might as well just burn the trees instead of coal, and leave the coal buried. 

As far as making coke.
I assume the microwave idea is actually with the goal of net energy production.  One still misses a chunk of the potential energy by making coke rather than complete combustion.  Perhaps you could bury it a couple of miles deep.  Think of the surprise when the future archaeologists find it in a few million years.

[Geezer]

Charcoal seems to be fairly stable stuff. Seems like an interesting idea.