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The Impact of Forests and Forest Management on Carbon Storage
- a condensation of Manriquez 2002, and Bowyer et al 2002 -
Bruce Lippke, John Perez Garcia, and Carolina Manriquez 1
Rural Technology Initiative, College of Forest
**For the PDF version of this thesis, click here.
Acknowledgement: This work was made possible by supplemental funding provided by Columbia Pacific RC&EDD and EPA. The modeling capabilities benefited by linking the findings of the Consortium for Research on Renewable Industrial Materials (www.CORRIM.org) with the Landscape Management System, a landscape planning system developed at the University of Washington (http://lms.cfr.washington.edu). A more in depth development of the methodology including economic considerations not covered here, are available in a Master's Thesis by Carolina Manriquez titled: Carbon Sequestration in the Pacific Northwest: a model, available in the library at the University of Washington. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the view of the funding agencies.
The Impact of Forests and Forest Management on Carbon Storage
Introduction: Many studies have noted that older forests generally store more carbon in the forest, hence reducing carbon concentrations in the atmosphere. Some studies have noted that the carbon pool in products is growing and is another important source of stored carbon. Recent studies show that the carbon emissions produced by the construction of steel or concrete buildings is considerably greater than it is for wooden buildings. The Kyoto protocol treats the flow of carbon from the forests into products as leakage, thereby ignoring the impact of management that supports the flow of wood into products, even though product storage is clearly increasing. This study tracks the movement of carbon from forest to forest products end uses, accounting for carbon storage and emissions at every stage of processing through to ultimate disposal. The displacement of carbon emissions from biomass energy conversion and substitution of non-wood materials are important aspects of a complete accounting system. A carbon tracking model is developed that forest managers can use to determine the impact of their management plans on carbon flows and storage pools. Reducing carbon emissions has become an international commitment and carbon trading or credit markets are developing. The objective of this project is to develop the full carbon cycle and carbon account as impacted by forest management decisions so that they can be supportive of constructive carbon policies.
Developing carbon accounts for forests and their products:
Carbon movement at the forest level:
For the estimates of energy consumed in forest management, harvesting, processing and construction, the findings of a several year research project by a consortium of 14 research institutions across the US (mostly universities) were used. The Consortium for Research on Renewable Industrial Materials (CORRIM), a not-for-profit university lead government research group, developed a research plan in 1998 to study the environmental performance of wood by developing a life cycle inventory (LCI) data base of all inputs and outputs from forest regeneration, through harvest, processing, construction, building use and final disposal. Their interim report was presented at the Forest Products Society 2002 annual meeting and is available at (www.CORRIM.org).
Forests store carbon as they accumulate biomass until disturbances
or natural mortality more than offsets growth. Disturbances can
be natural (fire, windstorm, disease) resulting in decomposition
of the biomass (carbon emissions) or a management treatment resulting
in at least a partial flow of the biomass into product storage or
energy production thereby displacing fossil fuel sources. Figure
1 shows the several pools of carbon in a Pacific Northwest forest
under a near optimum economic rotation of 40 years.
In most carbon accounting budgets, forest harvesting is usually considered to cause a net release of carbon to the atmosphere (a decrease in the carbon storage pool) as is evident at the 40-year harvest points in Figure 1.
Figure 2 shows the net forest carbon for different
management rotations. No-management is shown to store the most carbon
in the forest with the pool decreasing with shorter rotations.
Afforestation (conversion from non-timber uses) with no harvest clearly produces an increase in carbon stored at least until growth is offset by mortality. Longer rotations clearly store more carbon in the forest than shorter rotations, roughly twice as much by doubling the rotation. However, if products are removed from the forest, the accounting is incomplete by drawing the boundary at the edge of the forest as the exported product pools must be accounted for before all carbon impacts can be determined.
Carbon movement at the products level:
As more houses are built and the carbon stored in houses lasts
longer than the rotation age, the products carbon pool accumulates
from rotation to rotation. Figure 3 shows the products carbon pool
which is substantially impacted by rotation age with the shorter
(40yr) rotation age exceeding the products produced by the longer
(80yr) rotation until the first harvest of the 80yr rotation. Carbon
associated with the energy to produce the products is shown as a
If the short lived products are used as a biomass source for producing energy (co-generation), net electrical energy is added to the electrical grid, displacing fossil fuels, thereby providing another source of reduced emissions. While this biomass conversion is not subject to the decomposition of short lived products and therefore accumulates with every rotation, there is an energy conversion loss of about 50% compared to the initial carbon in short lived products as the efficiency of wood boilers is lower than natural gas or other fossil fuel sources. Figure 4 shows the carbon stored in the forest, in long lived products and the displacement of energy when the short term products are converted to energy. It takes several rotations for the biomass-to-energy conversion to significantly increase net carbon storage.
Since the substitutes for short lived wood products are likely to consume more energy than their wood based counterpart, one should expect that the carbon stored in short lived products would be greater than their energy conversion value.
Carbon displacement from substitute products:
The case for intensive management: