Can paper be carbon-neutral or even better?


by Simfish
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Simfish
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#1
Jan19-11, 05:19 PM
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They can only be carbon-neutral or better if sustainably harvested, of course. And only if the lumbar companies plant trees after they fall them.

But if these assumptions hold (which I believe they do in many regions of the U.S.), then cutting down trees helps sequester carbon. Trees grow fastest during their youth, and only for a finite amount of time. So if you want to sequester the most carbon, it makes sense to cut them down and to plant new trees. In fact, it's best to simply throw the paper away and to not recycle it (so the carbon doesn't get decomposed back into the soil, where it can potentially go back into the atmosphere).

As an additional benefit, land owned by timber companies cannot be used for other forms of development.

Now, of course, energy is involved in transporting the trees and in converting the trees into paper. That will put carbon back in the atmosphere. The question is, though, that is paper already carbon-neutral or even better in some regions? I'd imagine that it is in Washington and Oregon, where most of their electricity is already hydroelectric.
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NeoDevin
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Jan20-11, 12:15 PM
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If you simply throw paper away, it decomposes, releasing the carbon back to the atmosphere. If you recycle it, it stays in circulation as paper, thereby continuing to sequester the carbon.
Simfish
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Jan20-11, 01:53 PM
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They don't necessarily have to decompose though. Sometimes they end up in landfills that are sealed off from all oxygen

onomatomanic
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Jan20-11, 03:42 PM
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Can paper be carbon-neutral or even better?


Trees grow fastest during their youth, and only for a finite amount of time.
Is that really true? There's no question that their height increases fastest during their youth, but what matters is the increase in mass. To get evenly spaced growth rings, a tree's cross-sectional area would have to grow more and more rapidly each year, since this growth is proportional to the (ever-increasing) circumference.

Naively, it seems to stand to reason that a mature tree converts atmospheric carbon at a higher rate than an immature tree, simply because it has more leaves and thus more photosynthesis capacity. But it's possible that old trees don't put all of their capacity to use. Or that they invest a higher percentage into transient products like sugars (fruit), as opposed to the semi-permanent products like cellulose (wood). Or that they respire more than young trees. Et cetera, I honestly have no idea.

In fact, it's best to simply throw the paper away and to not recycle it (so the carbon doesn't get decomposed back into the soil, where it can potentially go back into the atmosphere).
In the bigger picture, there's nothing wrong with burning it, either, as long as it's burned instead of a fossil fuel and the energy gained is put to use. Whether that spoils the carbon-neutrality calculation depends on how one does the accounting, I suppose.
turbo
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Jan20-11, 04:18 PM
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Paper as it is currently manufactured is so far from carbon-neutral that it's ridiculous. Pulp and paper mills use copious amounts of steam for heat in the process (both pulping and paper-making). Most mills manage to generate steam with hogged-fuel boilers that use bark and wood waste. Most of the boiler-houses that I have worked in base-load with such materials, and take load-swings with oil, gas, etc.
Simfish
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Jan21-11, 01:15 AM
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Is that really true? There's no question that their height increases fastest during their youth, but what matters is the increase in mass. To get evenly spaced growth rings, a tree's cross-sectional area would have to grow more and more rapidly each year, since this growth is proportional to the (ever-increasing) circumference.

Naively, it seems to stand to reason that a mature tree converts atmospheric carbon at a higher rate than an immature tree, simply because it has more leaves and thus more photosynthesis capacity. But it's possible that old trees don't put all of their capacity to use. Or that they invest a higher percentage into transient products like sugars (fruit), as opposed to the semi-permanent products like cellulose (wood). Or that they respire more than young trees. Et cetera, I honestly have no idea.
Oh, those are very good points there (especially since we use growth rings to measure how old a tree is). So maybe it's not as carbon-neutral as I originally thought it was.

Paper as it is currently manufactured is so far from carbon-neutral that it's ridiculous. Pulp and paper mills use copious amounts of steam for heat in the process (both pulping and paper-making). Most mills manage to generate steam with hogged-fuel boilers that use bark and wood waste. Most of the boiler-houses that I have worked in base-load with such materials, and take load-swings with oil, gas, etc.
Okay, those are also good points. Although I can be corrected, I do give some probability to the belief that it might be carbon neutral in the northwest, where most electricity comes from hydro power. But on the other hand, buying more of a product in one region makes less of it available to consumers in other regions (who would probably buy from less carbon-neutral sources).
lisab
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Jan21-11, 10:53 AM
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The reason paper takes so much energy to make is because paper is made from cellulose, but wood is made from cellulose, hemicellulose, and lignin. Historical methods of separating out the cellulose use some combination high temps and mechanical grinding - both very energy intensive.

There has been on-again, off-again interest in using solvents to dissolve the wood into its consituents. If you're iterested, the process is called "solvent pulping" or "organosolv". I don't know if any manufacturers are using it currently.
turbo
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Jan21-11, 11:35 AM
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Quote Quote by Simfish View Post
Okay, those are also good points. Although I can be corrected, I do give some probability to the belief that it might be carbon neutral in the northwest, where most electricity comes from hydro power. But on the other hand, buying more of a product in one region makes less of it available to consumers in other regions (who would probably buy from less carbon-neutral sources).
Paper is nowhere being carbon-neutral anywhere. Probably the best efficiency you could get is in a recycle plant in which waste paper is turned into tissue, towel, etc. Even then the amount of steam required to dry the sheet is tremendous, as is the amount of energy needed to shred, pulp, and clean the waste material before it can be formed into a sheet, pressed and dried. Still, the only step you have saved is the thermomechanical or chemical pulping of the wood. You still have the energy-costs associated with collecting, baling, transporting waste paper.
DaleSwanson
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Jan21-11, 01:01 PM
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I've thought about this before and it makes sense to me. While I'll concede that if the power intensive manufacturing process is powered by fossil fuels it would likely be carbon positive, I don't see how it could possibly be anything other than carbon negative if the power was from carbon free sources (hydro or nuclear).

To restate the premise, you plant trees for the purpose of harvesting for paper in the future. The trees grow and absorb carbon. You cut down the trees and make paper. By using nuclear power, there is no sequestered carbon released from the manufacturing process. The paper is put into a landfill instead of recycled. In the landfill it is sealed off from oxygen and unable to release the carbon. Thus, the carbon that the tree absorbed is sequestered away long term. A new tree is planted and the cycle repeats. With each cycle, the carbon content of the paper is locked away in landfills instead of re-released.

Recycling won't sequester any carbon long term. It will only contain the carbon currently in the cycle. If we think about an ideal situation where all paper is recycled and there is no new paper added or removed it becomes clear that the total carbon locked up is (carbon in trees) + (carbon in paper), which won't change. With storing paper in landfills the total locked up carbon becomes (carbon in trees) + (carbon in paper) + (carbon in paper in landfills). Since the first two won't change (actually total tree mass may increase since there is a need to replace the paper), the fact that carbon in landfills will be continuously increasing shows that total carbon locked up increases.

This idea relies heavily on the idea that the power comes from carbon neutral sources, and that trees are only harvested for paper if they are planted expressly for that purpose.
plilja
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Jun10-11, 11:46 AM
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Quote Quote by turbo-1 View Post
Paper as it is currently manufactured is so far from carbon-neutral that it's ridiculous. Pulp and paper mills use copious amounts of steam for heat in the process (both pulping and paper-making). Most mills manage to generate steam with hogged-fuel boilers that use bark and wood waste. Most of the boiler-houses that I have worked in base-load with such materials, and take load-swings with oil, gas, etc.
Seems to me that if the boilers used in pulping and paper-making are fueled by bark and wood waste, then the fuel itself is also essentially carbon-neutral - as it comes from recently sequestered sources (trees) which would have decomposed anyway - all the carbon will be re-sequestered into new trees and re-burned again in the process, making the production process itself essentially a closed carbon cycle (if energy used for harvesting, planting and transport is not considered).


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