Words from the Wise

A study by a group of forest scientists confirms forest-derived bioenergy results in no net carbon release
By Anna Austin | January 25, 2012

Does the utilization of wood for energy release as much pollution as energy from coal? Does it release more? Is it depleting our nation’s forests and destroying natural habitats?

These questions are hotly debated by scientists, foresters, bioenergy industry members and even the general public. While  it’s likely the real answers lie somewhere buried beneath a discombobulating mountain of studies, reports and whitepapers—many of which have been conducted with a very specific purpose or outcome in mind—it’s left policymakers and landowners unsure about what’s fact and what’s fiction.

A recently released study authored by nine scientists from multiple organizations  and universities, including the U.S. Forest Service, may be poised to clear up some confusion. With no motive other than to scrutinize, hash out and compare the best and most recent science surrounding forests, climate change and bioenergy from a forest management perspective, the group is confident in its findings and hopes they will be accepted as the unvarnished truth.

Carbon: Biogenic vs. Geologic

The study “Managing Forests Because Carbon Matters: Integrating Energy, Products, and Land Management Policy” is an update to a previously released report initiated by the Society of American Foresters, and was put together by a task force of people who had all been involved in forest and carbon accounting aspects. It took about 10 months to complete, according to lead author Robert Malmsheimer, professor at the State University of New York College of Environmental Science and Forestry.

Overall, the study has one major finding with a few main supporting conclusions. So what’s the bottom line? “As long as you manage forests sustainably, you can produce bioenergy and help address some of the issues surrounding climate change,” Malmsheimer says, segueing into the first supporting conclusion. “We can provide carbon benefits through both storage in forests and through substitution benefits, while providing all of the other benefits that forests normally provide society.”

The fact that it’s not necessarily either/or is an important point, he emphasizes. “We can still have the wildlife benefits, the recreation benefits and all the things people use forests for, all while still managing them for carbon.”

But that doesn’t mean every forest should be managed for carbon. “It’s really the landowner’s decision, but we wanted to be able to provide them with the correct scientific background so if they decide they’re potentially interested in managing for carbon, they have that science available to help them decide,” Malmsheimer says.

The second main supporting conclusion of the study is that energy produced from forest biomass returns to the atmosphere carbon that plants absorbed in the relatively recent past, and therefore it essentially results in no net release of carbon.

“An important thing to think about here is that CO2 levels in the atmosphere have been relatively stable for hundreds of thousands of years,” Malmsheimer explains. “The issue we have in regard to climate change is that what we’re doing is taking carbon that’s been sequestered in the earth—from the start of the industrial revolution up until now—and we’ve been emitting it into the atmosphere at such a rate that the atmosphere can’t assimilate it.”

Simply put, burning coal takes geologic carbon—carbon stored in the earth—and adds it into the atmospheric cycle. When a tree sequesters carbon through photosynthesis, it’s absorbing carbon that’s already in the atmosphere. “So when you are creating energy [with wood] you’re using that atmospheric carbon and simply putting it back into the atmosphere; you’re recirculating it. When you’re producing energy from coal, you’re taking stored geological carbon and adding more CO2 to the atmosphere.”

It seems like a simple concept, but people have a hard time grasping it, Malmsheimer says. “When explained in this way, I think it makes a lot more sense to people.”

All of these ideas are only relevant, however, if forest inventories are stable or increasing. Is that really the case in the U.S.?

Sustainable Forestry

“It is the case, and has been for the last 70 years,” Malmsheimer says. “However, there are parts of the U.S. where it hasn’t been the case for all of those years, so it depends upon the spatial scale you’re looking at.”

When asked whether U.S. forests are being sustainably managed, study co-author Jim Bowyer of the University of Minnesota’s Department of Bioproducts and Biosystems Engineering says yes and no. “Yes because the forest area in what is now the U.S. is within one percent of what it was 100 years ago,” he explains. “Net growth nationwide has exceeded removals for over 70 years continuously, and as a result, standing timber volume has increased steadily over that period as well.”

At the same time, there are areas where forest inventories aren’t necessarily stable or increasing, but it really isn’t because too many trees are being removed for energy.  “Many forested areas, including much of the federally designated national forest lands, are not being managed at all,” Bowyer says. “Some of these areas currently support numbers of trees and overall biomass volumes that are well-above historic levels, a situation that is increasing the risk of serious insect infestation and disease incidence, and fueling rising incidence of catastrophic fire events.”

He adds that there are, however, instances of increasing fragmentation of forest lands due to expansion of urban areas and home development in forested areas. That trend could potentially threaten stability of forest-dwelling wildlife species, opportunities for management, and sustainable timber production.

Moving away from forest management, another point in the study is that there are some real benefits to using wood in place of other materials. “The study is really designed to try to specify what those benefits are,” Malmsheimer says. “One is that forest products require less fossil-based energy to be produced, and also, when you produce anything out of wood you’re storing carbon for some length of time; sequestering it in whatever it is.”

The authors of the study do recognize that a large percentage of the future U.S. energy portfolio will come from a variety of sources, including wind and solar, but none of them sequester carbon, Malmsheimer points out. “And, a lot of technologies still need a lot of work to be adapted on a widespread basis.” 

When asked about how this study’s findings compare with the infamous Manomet Center for Conservation Sciences study, which crafted a debt-then-dividend model for forest bioenergy carbon emissions, Malmsheimer says the Manomet study had a very specific purpose and a very specific question, which was answered. “The problem with that study is that the question was wrong: what is the carbon accounting on a single plot of land? We don’t manage just one plot; we manage hundreds of thousands of stands. Granted, some stands are just getting to a point of carbon deficit, and some are further away, but you have to look at multiple stands over long periods of time. It’s impossible for [wood energy] to be worse than coal, because you have to go back to the very basic idea that with coal you’re taking geologic carbon and putting it into the atmosphere.”

Though the team had the study in mind, Malmsheimer says it was not intended to be anti-Manomet. “We believe we provide information in our report that addresses it directly, but we were much more interested in a broader look at forests and carbon accounting and wood products. There are a lot of people who have done those kinds of analyses and we didn’t think it would be helpful to have one more.”

Instead, the study is intended to serve as a guide for not only landowners, but policymakers as well.

Pushing for Sound Policy

From Bowyer’s perspective, policy shouldn’t be influenced by anything other than science.  “In all environmental decision making, we need to move as rapidly as possible away from decisions based on intuition, emotion, and politics to decisions based on scientific, systematic and comprehensive assessment of the likely environmental impacts of possible alternatives,” he says. “One key is far greater use of life-cycle assessments (LCA) in environmental decision making.”

There is one caveat, Bowyer says. Assessments must follow international protocols for the conduct of life-cycle inventory and assessment, as spelled out in the International Organization for Standardization (ISO) 14000 series. “Several recent studies of biogenic carbon emissions that have supposedly been based on LCA have completely ignored established protocols, with the result that their findings are completely meaningless. Nonetheless, they have still been dutifully reported in the media.”

Malmsheimer says the group is working on publicizing its study, and perhaps most important, getting it into the hands of policymakers. Because studies such as this one generally have a technical nature and are oftentimes difficult for congress members to fully comprehend, Bowyer has authored a nontechnical, 15-page version through Dovetail Inc., an authoritative information company focused on the impacts and trade-offs of environmental decisions, including consumption choices, land use, and policy alternatives. “Realizing that most decision makers at all levels of government are, in fact, not scientists, we prepared the Dovetail summary with the goal of bringing a summary of recent science on forests and carbon balances to those people so as to provide a basis for reasoned and informed debate,” Bowyer says.

As to whether he thinks the study will influence policymakers, Malmsheimer says the team hopes so. It has sent a copy of the study to state landowner organizations and is working on a two-page summary for Capitol Hill. “We’ve learned it’s not ‘if you build it, they will come,’” he adds. “You have to build it, and then bring it to them.”

Author:Anna Austin
Associate Editor, Biomass Power & Thermal
(701) 751-2756


3 Responses

  1. Jack Haley



    The comment the renewable energy does not "..sequester carbon...." is a non-sequiter - renewable energy avoids the emission of more carbon. Forests only sequester carbon on a temporary basis - even wood in houses only stores carbon for the life of the house, maybe 50 years on average. Forests do not remove carbon from the atmosphere permanently unless they are planted on virgin land and retained forever.

  2. John Christie



    Wood for energy can reduce pollution dramatically – but not everywhere; and not for everyone. Wood for energy is an important opportunity to be pursued because under the right circumstances it can result in energy plus a managed forest, and improve the earth’s ability to sequester more atmospheric carbon than it creates. Many technologies need to be developed, but here is one that will work within an integrated forest economy. A pyrolysis system that effectively separates the hydrogen from carbon of cellulose in wood residue can produce energy at rates that are competitive with other forms of electricity generation in remote areas. Where wood residue is available from an established forest industry, an investment in a pyrolysis based co-gen system produces electricity that can be sold with a 30%+ IRR, reduce GHG’s by over 36,000 Tonnes from a 2 mWe plant, provide ancillary industry jobs, and free up the waste-clogged forestry industry in remote communities. Such a solution is badly needed in the hundreds of remote communities around the world that have access to wood residue. Initial installations will happen on the west coast of Canada and United States beginning in 2012. One of the keys to the opportunity for the pyrolysis solution is that, of all the bioenergy systems, only pyrolysis provides biochar – which in effect sequesters a large portion of the carbon along with all the nutrients from the tree… which can be used to regrow new cellulose and to sequester more carbon in areas that have poor soil conditions. This is accomplished within a sustainable forest industry, and in fact raises the productivity of forest harvesting operations. Some numbers will help to illustrate: from the processing of a Tonne of forest mass (i.e. the mass of wood removed from the forest to become finished wood products and residue), and utilizing the residue in a pyrolysis based co-gen system, a net reduction of 0.38 T CO2e can be achieved. This GHG reduction is based on three main contributors: avoided decomposition of the residue (264 kg), displacement of the diesel fuel used to generate electricity now (257 kg), and enhanced regrowth of wood due to selective application of the biochar (198 kg). These sequestration methods more than offset the 364 kg CO2e released by the electricity generation from the hydrogen/CO2 syngas combustion… to the tune of 379 kg. Besides this GHG reduction and the electric power generation (361 kWh), a total of 722 kWh of heat is produced at no additional cost, and this will be used for ancillary operations like a dry kiln – which will be an added benefit the remote community forest industry. In this case, there is a definite synergy between the forest industry and community need for electrical energy while creating jobs and making a net reduction in greenhouse gases. This scenario does not work for all communities near forests, but in the case of remote communities, it is a very good fit. That addresses Malmsheimer’s first point that (in some communities) ”As long as you manage forests sustainably, you can produce bioenergy and help address some of the issues surrounding climate change” . Relative to his second, that forest stored CO2 is recirculated whereas burning geologic carbon, like coal, is adding carbon to the environment… we can say that this pyrolitic technology not only recirculates the carbon, but it also has a net reduction benefit….offsetting (ever so slightly) the release of geologic CO2 into the atmosphere. As to the Manomet study, this technology looks across regions both fertile and not, and provides an economic model for increasing the fertility of areas that will otherwise remain barren, and never help to sequester any carbon.

  3. PT Wise



    TO Jack Haley Name a virgin forest that has retained its carbon forever? There is a carbon cycle and trees and oceans participate in it. Photosynthesis, the capture of CO2, and release of O2 Oxygen - and the C is retained as carbon with the tree, Trees sequester carbon most rapidly in their first 30 to 40 years of life. 90% of the energy required to support 7 billion people comes from burning somethings fossil fuels (85%) and most of the rest is biomass. It all puts carbon in the air. The only difference is that fossil fuels take carbon buried in the earth for 2 million plus years and put it into the atmosphere with never a way to return it. Personally, I'll bet on biomass.


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