From Duke University and the Department of Obvious Science comes this study partially funded by NASA:
Standing trees better than burning ones for carbon neutrality
DURHAM, N.C. — The search for alternatives to fossil fuels has prompted growing interest in the use of wood, harvested directly from forests, as a carbon-neutral energy source.
But a new study by researchers at Duke and Oregon State universities finds that leaving forests intact so they can continue to store carbon dioxide and keep it from re-entering the atmosphere will do more to curb climate change over the next century than cutting and burning their wood as fuel.
“Substituting woody bioenergy for fossil fuels isn’t an effective method for climate change mitigation,” said Stephen R. Mitchell, a research scientist at Duke’s Nicholas School of the Environment. Wood stores only about half the amount of carbon-created energy as an equivalent amount of fossil fuels, he explained, so you have to burn more of it to produce as much energy.
“In most cases, it would take more than 100 years for the amount of energy substituted to equal the amount of carbon storage achieved if we just let the forests grow and not harvest them at all,” he said.
Mitchell is lead author of the study published in the peer-reviewed journal Global Change Biology Bioenergy. Mark E. Harmon and Kari E. O’Connell of Oregon State University co-authored the study.
Using an ecosystem simulation model developed at Oregon State, the team calculated how long it would take to repay the carbon debt – the net reduction in carbon storage – incurred by harvesting forests for wood energy under a variety of different scenarios.
Their model accounted for a broad range of harvesting practices, ecosystem characteristics and land-use histories. It also took into account varying bioenergy conversion efficiencies, which measure the amount of energy that woody biomass gives off using different energy-generating technologies.
“Few of our combinations achieved carbon sequestration parity in less than 100 years, even when we set the bioenergy conversion factor at near-maximal levels,” Harmon said. Because wood stores less carbon-created energy than fossil fuels, you have to harvest, transport and burn more of it to produce as much energy. This extra activity produces additional carbon emissions.
“These emissions must be offset if forest bioenergy is to be used without adding to atmospheric carbon dioxide concentrations in the near-term,” he said.
Performing partial harvests at a medium to low frequency – every 50 to 100 years or so – could be an effective strategy, O’Connell noted, but would generate less bioenergy.
“It’s a Catch-22,” she said. “Less intensive methods of harvesting release fewer emissions but yield less energy. The most intensive methods, such as clear-cutting, produce more energy but also release more carbon back into the atmosphere, prolonging the time required to achieve carbon sequestration parity.”
Given current economic realities and the increasing worldwide demand for forest products and land for agriculture, it’s unlikely that many forests will be managed in coming years solely for carbon storage, Mitchell said, but that makes it all the more critical that scientists, resource managers and policymakers work together to maximize the carbon storage potential of the remaining stands.
“The take-home message of our study is that managing forests for maximal carbon storage can yield appreciable, and highly predictable, carbon mitigation benefits within the coming century,” Mitchell said. “Harvesting forests for bioenergy production would require such a long time scale to yield net benefits that it is unlikely to be an effective avenue for climate-change mitigation.”
The research was funded by a NASA New Investigator Program grant to Kari O’Connell, by the H.J. Andrews Long-term Ecological Research Program, and by the Kay and Ward Richardson Endowment.
Greenies have quite seriously proposed cutting and burying, or cutting and entombing in plastic. Fortunately the money ran out before those fantastically wasteful ideas were implemented.
I wonder if these researchers have ever noticed what actually happens to wood in rich countries? It isn’t burned. It becomes houses, which presumably “sequester” the CO2 for several decades. Only the leftover bits are chipped into burnable wood.
Gosh, I would have thought that RJG would have funded this at the LSE via the Grantham Institute. He has been into timber for at least 15 years at GMO. Ah well, Lord Stern, you missed your chance to be a loon again. Just as well, the previous times were enough.
There is a counter argument, relevant to the longer term. Almost all the carbon reduced by photosynthesis is going to be oxidized again eventually, either by respiration (rotting, insects) or wildfire or, possibly, in a power station. So leaving the wood gives some temporary carbon storage, but eventually releases the energy of reduced carbon without benefit, and still ends up as CO2. Burning in a power station forgoes the storage, but means that some smaller amount of fossil fuel is not burnt to provide that electricity.
I think the long-term arithmetic favors power stations. You can also get part of the storage benefit with delayed harvesting.
It’s also true that whatever you do, you’ll end up with a maximum forest storage for the land and water available. Then you can’t add to the carbon store. But you can still burn the wood to displace fossil fuel use.
@polistra Yes, sawdust/chips are used for pellet stoves pellets. But they are also combined with various plastics to make building material. With the lumber demand down of late, sawdust has been harder to come by. Nothing left but the squeal and all you know.
dccowboy says:
May 31, 2012 at 3:23 pm
Burning wood also produces dioxins but the greens don’t seem to count toxins from wood, only coal.
I’m quite sure that the conclusions reached by this study are counter-intuitive to most supporters of CAGW alarmism.
Now, I’d like to see a similar study done on Wind and Solar energy. Given current efficiencies, I have a feeling that the results will be the same. Who thinks I’m wrong?
Nick Stokes,
You’re getting way ahead of yourself. First, you need to provide evidence that the increase in CO2 is causing global harm. If so, then we can worry about how to handle it.
But so far there is no such evidence. None. You might just as well be worrying about a herd of unicorns.
First, evidence. Then, response. You’re doing it wrong, discussing a response sans any evidence of global harm due to anthropogenic CO2. That’s not science, that is advocacy.
Nick, it seems as if this study would have do this exact arithmetic. Otherwise, I’m left wondering exactly what arithmetic they did. I’d be surprised if their arithmetic did not assume harvesting mature woods.
However, if you’re implying that it’s better to burn fallen trees rather then allowing them to rot, then I would encourage you to calculate the energy required to selectively harvest only fallen trees. You might learn that less carbon is released via rotting than selective harvesting. Unless of course, you intend to harvest fallen trees using unicorn power.
“Given False Premise, Dumb Idea Still Dumb. Solution? More Money And Power For Us.”
You see, things like this are why the word “academic” carries the connotation of “pointless.”
Smokey, *they* want to argue the “GW” part of the acronym, and will dodge the “C” part relentlessly, except when they control the forum and can assert without contradiction (closed fora).
Because, as you say, the proof is illusory (or its new synonym, “extensively modeled”).
Did the study give actual productivity numbers? They say that “Wood stores only about half the amount of carbon-created energy as an equivalent amount of fossil fuels.” That seems to say we need twice as many trees.
Dave Worley says:
May 31, 2012 at 4:35 pm
Younger trees sequester more carbon than older trees.
What gives you that idea? Consider the surface area of an older tree compared to a younger tree. How many younger trees do you need to equal one older tree? And what acreage would you need for each?
However, your comment leads to an important point about forest management. A healthy forest will take up more CO2 than a sick forest. The Bambi syndrome makes people think people should stay out of the forest and let nature manage it. Too late for that.
In US forests, tree density can be 10 times higher than in the historical condition. Read John Muir, and you’ll realize few places retain the “park like” quality he observed in the late 1800s. Forests have less biodiversity when they are crowded. They become an extreme fire hazard. Catastrophic fires did not occur in the past they way they do now. The reason is, fires were once more common, and any large stands of old trees with too high density would burn at some point. Also, crowded young trees would burn too. Open meadows were maintained; they are disappearing now. The forest-meadow interface has the greatest biodiversity.
Burned trees only give off part of their sequestered CO2. As they decay, 2 or 3 times more CO2 than produced in the fire can be released before they are gone. Burning wood doesn’t sequester CO2, but building houses and furniture does. Our forest policy restricts cutting to a very small percentage of the wood mass produced each year. That policy is clearly unsustainable. To achieve stability, we need to cut an amount of trees equal to the amount that is produced each year.
Forest restoration should be a policy goal. It’s good for the forest and the wildlife in it. Dense trees compete for water, and can die because they can’t get enough water to supply their leaves or needles. They can be weakened to the point they are prone to larval infestation, and can die that way. Wildlife can’t run from fire successfully. Most wildlife can’t survive in dark, crowded forests.
Humans have managed forests for thousands of years. There is no reason we should stop now. We just need to implement the correct policies. Based on public information available in Sequoia National Park, at least the National Park Service does seem finally to understant, even if the USFS doesn’t.
Used to be that Cow College focused on how to grow trees for LUMBER. As in building things. Creating jobs. Caring for our forests so they are more PRODUCTIVE. Those two words, lumber and productive, can cause a watermelon to have a seizure!
The cost of creating large holes to fill with trees, plus transport, would be far greater than the gains. There is a high demand for landfill sites for other materials.
It’s not only the carbon in trees that enters a cycle when you use them for fuel. They might be carbon- neutral by the definition of somebody, but they are not potassium-neutral, phorphorus-neutral, sulphur-neutral, magnesium-neutral, etc.
You can’t keep harvesting trees and regrowing, without supplementing with fertilizer, which often comes from remote places with high transport and GHG emission costs. You have to factor in an investment cost, because to buy land, clear it, plant trees, thin them, fertilise them, takes up-front money that might not see a return for 15 years or more.
Please consider that these comments have been known for decades and that if there was a positive return in the suggestions, they would be mainstream practice by now.
Well I wouldn’t say burning the wood is a great idea, but clear cutting the forests, and replanting (in blocks of course) is a good idea. Juvenile growing forests are a carbon sink; old growth forests are not; they are carbon neutral, so they don’t do a thing for the CO2 balance. Now old growth forests are good for other reasons, so I am not in favor of cutting them; but tree farms are far more efficient as carbon sinks; burning their product (wood) is not.
indegar says:
May 31, 2012 at 4:50 pm
Yes!!!!!!
That said, why do we want to sequester carbon?
Wobble, Most tree plantations of hardwood and many of softwood are to provide building material from saw logs or chipboard. The management regime is often tailored to maximum return of yield, quality and low cost of saw logs. If this management is inconsistent with green desires to cycle CO2, then sorry, it’s no go. The world still awaits definitive, quantitative evidence of detriment from CO2 in the air, no matter how hard one wishes for it.
Ahem… dead wood (standing or fallen down) is preferred by folks who regularly cut firewood for their winter heat. Dead wood is partially to fully dry, reducing the drying time required before the fuel can be burned. Green wood from living trees is harder to harvest, heavier to haul, split, and stack, as well as taking substantially longer to dry.
Additionally, harvesting the standing or down dead wood from the forests reduces the available fuel load and the potential for catastrophic forest fires. It’s really quite basic.
Old growth forests store carbon. If you lose the old growth forest, then you lose the storage. That most certainly affects the CO2 balance.
I understand. However, I don’t think this study specifically addressed this issue. I think this study was specifically looking at two possible methods for reducing atmospheric CO2.
1. Forest management tailored towards the production for woody mass energy as a replacement for fossil fuel; versus management.
vs.
2. Forest management tailored towards carbon storage within the woody mass.
It seems as if they concluded that #1 is a failure – that it’s better to burn fossil fuels than to produce woody mass for energy. And it seems as if they concluded that #2 would successfully reduce atmospheric CO2.
Yes, I know. And until the evidence exists there’s no point in implementing #2.
BUT the study suggests that there’s no point in implementing #1 even IF the evidence existed.
wobble says: May 31, 2012 at 7:03 pm
“However, if you’re implying that it’s better to burn fallen trees rather then allowing them to rot, then I would encourage you to calculate the energy required to selectively harvest only fallen trees.”
Wobble, I’ll defer there to
indegar, who seems to know what he is talking about. The excess biomass is currently gathered. It will turn to CO2 in any case. It might as well be used.
Spanner in the works
FOREST FIRE
“Hoser says:
May 31, 2012 at 7:10 pm
Dave Worley says:
May 31, 2012 at 4:35 pm
Younger trees sequester more carbon than older trees.
What gives you that idea? Consider the surface area of an older tree compared to a younger tree. How many younger trees do you need to equal one older tree? And what acreage would you need for each?”
They grow more slowly when they are mature, Young trees grow rapidly and stash away carbon rapidly. Once they mature, less carbon is being stashed away per acre per year. That’s when its time to harvest and store the carbon in a building. Otherwise the wood ends up on the forest floor, releasing carbon into the atmosphere.
Not that I am bothered by co2 in the atmosphere, just responding to the idiotic premise.
Not that I am against old growth in the national parks either. Some natural forests should be retained for posterity and scenic beauty.
Did they include the expected forest fires? Are they expecting the forests to grow and crowd out everything else in there possible growing regions? You know like crops, cities, etc…
Burning biomass is just an inefficient method of collecting and distributing solar energy. And equally clearly if you cut and burn some of it then the amount sequestered will on average be a bit less than if you don’t cut it. So I guess what they are saying is that the amount less sequestered is greater than the bit less of fossil fuels that they would need to burn without the biomass. In the short term this may be true, but overall if you are using solar energy in place of fossil fuels you must have less carbon in the atmosphere/ocean/biome than otherwise. Once the forests have reached there maximum extent the carbon will just be cycling between atmosphere, oceans, and biome. and the carbon from fossil fuels will be an additional amount. It is only in the realitively short time when the forests are increasing or that a difference will be made
A silly study. Obvious and trivial.
Meanwhile, back at the ranch, Tonto, cleverly disguised as a forest not allowed to burn naturally/periodically, is losing biodiversity at an alarming rate. Below the old-growth canopy, not a heck of a lot is, you know, alive. Take THAT you evil, twisted, forest you!