WBA disputes forest biomass carbon payback, debt theories

By Erin Voegele | December 11, 2012

The World Bioenergy Association released a new biomass fact sheet at the United Nations Climate Change Conference (COP18) in December. The fact sheet, titled “The carbon neutrality of biomass from forest,” asserts that theories on carbon debt and “payback time” of biomass are not credible. According to the WBA, these assumptions are based on the unrealistic assumption that trees are burned before they are grown.

The fact sheet notes that replacing fossil fuels with sources of renewable energy must be the core strategy utilized within future climate policies. Utilizing biomass from sustainably managed forests can play an important role in this strategy,” said the WBA in the document. “Several countries have demonstrated that a buildup of carbon in forests and an increase of forest biomass for energy is simultaneously achievable by good forest management practice.”

While some organizations have argued that woody biomass should not be harvested in an effort to increase carbon dioxide storage, the WBA stresses that strategy isn’t feasible because forests stop growing as soon as their trees mature. In addition, the stored carbon in those mature forests will be released through decay, even if the biomass isn’t burned for energy.

In the fact sheet, the WBA outlines four stages of growth that each tree experiences, including planting and first establishment, growth, maturation and decay. According to the paper, each tree constantly absorbs carbon dioxide by photosynthesis and release carbon dioxide through respiration. “Until a tree progresses to its mature stage it is growing and absorbs more CO2 by assimilation than it releases by breathing,” said the association in the document. “In this phase the tree is a carbon sink. In the mature phase CO2 uptake and release are in equilibrium, the tree is carbon storage. As follows, during the decay phase, a tree will become a net carbon source.”

Rather than preventing the harvest of woody biomass, the association is urging governments to enforce sustainable forest management policies. According to the WBA, this can be accomplished through the use of sustainability criteria it has developed in combination with a biomass certification system.

A fully copy of the fact sheet can be downloaded from the WBA website.




5 Responses

  1. Josh Schlossberg



    "forests stop growing as soon as their trees mature." I'm not sure I've ever seen a scientific study suggesting this. The growth might slow, but it doesn't stop. These sorts of statements don't make the biomass power industry seem very informed and/or genuine.

  2. Joe Zorzin



    Josh, you're right that the claim forests stop growing is false, at least for a very long time- but, that fact in and of itself is not a strong claim against woody biomass- when done right, and by that, I mean CHP or thermal, certainly not electric. The Manomet Report slammed biomass for electricity. There are many benefits to the use of biomass done right- it's good for the forests and forest economy. All forms of energy production have some negative qualities, for example, a 17 acre solar "farm" built in my town in north central Mass. which is now a desert covered with metal and glass. Shockingly (to me) there was ZERO opposition to the solar "farm" by any enviro group and by those folks so fiercely oppossed to the biomass plants. Why not? Those who oppossed the big electric biomass plants in Mass. should accept or at least tolerate biomass for CHP and thermal, when the wood will come ONLY from well managed forests. Joe Zorzin MA Forester Lic. #261

  3. William Strauss



    The paper is pretty clear in showing that the amount of wood on a hectare stabilizes after many decades and the forest is no longer a net carbon sink. This does not mean that growth of trees stops but only that the number of cubic meters of wood that can live on a hectare is limited by the carrying capacity of that space. The forest is in equilibrium. The equilibrium varies by land and climate but the growth of the mass of wood on a given space is not without bounds.

  4. Robbo Holleran



    Biomass is a "carbon benefit" when applied to managed forests. In the normal course of a wide range of forest management activities, large amounts of debris are routinely left to rot, with no energy benefits. Utilizing this material for energy, at any efficiency (including "mere electric generation") has the potential carbon benefit of replacing fossil fuels. On the issue of forests stopping growth, this certainly applies to each tree: the four stages mentioned. In a maturing forest, many trees will get to a slow growth phase, and death/decay. Our Northeast forests have replacement trees in an understory at that phase, but death and decay can exceed growth. Some of the dry western forests have expanses of dead trees, without effective replacements. Of course, they often burn, releasing their carbon and far more pollution, with other ecological costs, such as loss of stream buffers, soil nutrients, etc, that far exceed forest management problems. As a forest manager, I find biomass harvesting a particularly useful tool for achieving a wide range of silvicultural goals, especially in forests with a high percent of low quality trees, and being nearly 100 miles from any pulp markets. Forest management has a wide range of social and ecological benefits,and biomass, to me, is merely a by-product.

  5. Don Wakoluk



    While carbon storage capacity within mature forests slows, here in Massachusetts it is common for the understory to continue rapid growth of invasives. There is no overall strategy being put forth for the mgt. of these invasives as they skip through micro ecologies and dominate biogeocenes, eliminating native competition. There is little financial incentive to manage these invasive populations via mechanical removal methods and even some poorly planned, sporadically funded incentives by state and federal govt. to chemically control these populations. Do we just throw up our collective hands and give up mature forest mgt. as these invasives replace native ecosystems? Future natural resource managers will credit the loss of our New England forests to global warming chiefly to inaction from "organized environmental groups" to stop the spread of these ivasives today while it can be accomplished via biomass harvesting.


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