Wood has become an attractive material for its biobased/biophilic and perceived carbon benefits. However, for reasons detailed below, current practice can make it difficult to know the true climate profile of wood products. This said, innovative methods are emerging to overcome this challenge.
Understanding the utility and limitations of Life Cycle Assessment (LCA) and Environmental Product Declarations (EPDs) for wood products is fundamental. LCA is a method for quantifying the environmental impacts of a product or an entire building project throughout its life cycle. During the design and procurement process, EPDs are increasingly used to gather data on specific products as a basis for considering and comparing different materials, for different suppliers of the same material, and to run calculations for Whole Building LCAs.
EPDs are independently verified documents that report on a range of environmental impacts estimated by an LCA study, including global warming potential, acidification, eutrophication, and others. When LCA studies are conducted for individual companies or supply chains and the results are reported in product-specific EPDs, it is possible to compare the carbon footprint of competing products of the same type and/or that of different materials that can be used for the same purpose. This allows specifiers and purchasers to select the product that has less negative environmental impacts and feed that information into Whole Building LCAs in pursuit of reducing a building’s overall embodied carbon.
Why then doesn’t CSWG’s guidance include LCAs and EPDs as a procurement option for CSW?
The answer is that while they can be used to compare emissions associated with manufacturing and transporting a product, contemporary EPDs do not meaningfully capture nor convey the “climate smartness” of wood products because net emissions or removals associated with observable changes in forests due to management practices are not accounted for in the underlying LCA models. In other words, current LCA methods used in the forest sector do not account for readily observed changes in forest carbon stocks resulting from forest management activities across managed landscapes over time. The magnitude of these changes can dramatically increase or reduce the true carbon benefit or burden attributable to a wood product.[1]
Instead, nearly all North American (and European) wood EPDs adopt the “biogenic carbon neutrality assumption” which assumes carbon gains from forest regrowth in a managed forest are exactly equal to the amount of carbon emitted from soils, logging slash (branches, leaves and needles), and roots through decay or burning post-harvest, as well as emissions resulting from the conversion of logs into finished wood products.[2] This assumption is often invoked so that emissions of “biogenic carbon” that occur during the processing of logs into finished products can be conservatively ignored.[3]
According to the international standards that govern LCAs and EPDs, the biogenic carbon neutrality assumption can be invoked if forests are “sustainably managed” under 3rd party certification or through national-scale reporting under the United Nations Framework Convention on Climate Change (UNFCCC). In the latter case, the assumption rests on estimates that overall forest carbon stocks—or forest area—at a national level are stable or increasing, including both actively managed and unmanaged forestland (including protected areas)[4].
This obscures the critical underlying reality that no managed forest is exactly carbon neutral. Through the lens of LCA, wood products from forests that represent a wide variety of management practices and starting conditions[5] are treated the same — the only differences captured are in emissions resulting from a given company’s use of energy and fossil fuels in timber harvest and downstream manufacturing and transportation. Yet, the carbon benefit of CSF can easily outweigh all these other factors combined. In other words, current LCAs and EPDs for wood provide no advantage to companies that practice or source wood from CSF, and thus they have limited relevance in CSWG’s procurement guidance.
LCAs and product-specific EPDs for materials other than wood promote internal competition among companies within the industry in question to reduce their net emissions. However, the assumption of forest carbon neutrality blunts this effect in the forest products industry.
Research on improving standards for forest product LCA and corporate greenhouse gas reporting more generally to address this blind spot is underway. CSWG guidance regarding the use of LCAs and EPDs will change when science-based methods for factoring forest carbon stock changes into LCAs and translating those changes into EPDs for wood products are developed.
The assumption that all forestry is carbon neutral makes it impossible to differentiate timber suppliers or supply areas based on observable increases or decreases in carbon stocks occurring in different forests managed in different ways. The fact is that many forest managers are intentionally increasing carbon stocks as a CSF strategy while others may have flat or decreasing carbon stocks in their forests over time.
Until and unless LCAs and EPDs improve, measuring the carbon stock changes in forests in a given woodshed[JG1] and allocating this value to the products coming out of it offers a way to more accurately calculate a wood product’s true carbon footprint: this is the Forest Carbon Stock Factor approach.[6] This is an emerging method that relies on publicly available forest inventory information and geospatial monitoring to calculate the change in forest biomass and the volume of timber outputs from a supply area over time.[7] The division of the former by the latter yields a factor that can be incorporated into EPDs as a carbon benefit or burden associated with each unit of industrial roundwood (i.e., logs) coming from that area, thus correcting the assumption that managed forests are all exactly carbon neutral. The calculation of such factors can be used in procurement options 2 (Intentional Sourcing of Climate Smart Wood) and 3 (Certified Wood) provided there is disclosure of information about the forests that a mill sources from (levels 2 or 3).
Carbon stock change factors can be calculated in one of two primary ways based on scale and granularity, both of which require nuanced interpretation to justify claims of climate-smartness. As a novel and innovative approach, the specific methods, data sources, and understanding of precision and uncertainty in their use are evolving and expected to improve over time — and project teams who adopt it and share their experiences can help advance its improvement.
Carbon stock change data can be found reported by landowner types at county-, multi-county, or regional scales. Thus, the application of stock change factors to projects should incorporate traceability and transparency down to the level of the primary manufacturer supply area at minimum (Level 2) and to the level of the source FMU if possible (Level 3). More precise estimates may be employed where timber supply can be traced to specific owner types (e.g., industrial, federal, tribal, state) or to specific ownerships.
Pros
Cons
Forests where carbon stocks are growing over time are a sink for atmospheric carbon. This occurs when forest growth exceeds timber harvest and natural mortality and disturbance. Declines in forest carbon stocks over time represent a source of carbon to the atmosphere. Negative carbon stock change factors indicate a net gain of forest carbon stocks in the timber supply area and may be considered an upstream embodied carbon benefit, while positive carbon stock change factors indicate a net loss of forest carbon stocks in the timber supply area that represent an upstream embodied carbon burden.
Carbon stock factors can be multiplied by the Global Warming Potential impact derived from an LCA study and reported in a product-specific EPD to correct for the carbon neutrality assumption.
Even without directly tying the carbon stock change values to the building, these factors and thresholds of performance could be used as criteria for choosing among suppliers. By comparing carbon stock change factors between timber suppliers within and across regions, wood purchasers have the option to steer procurement towards suppliers that are adding more carbon to the landscape than their counterparts.
However, carbon stock change factors should not be used as the exclusive indicator of climate-smartness. There are no absolute thresholds for designating a timber source as climate smart based solely on carbon stock change factors. To be used to characterize climate-smartness, carbon stock change factors should be interpreted within the relevant regional context considering forest ecology and management practices. This approach also does not address improvements or harms other important dimensions of CSF such as ecological integrity, biological diversity, soil and water quality, etc.
The approach is also complicated by the fact that in certain regions and forest types climate-smart forestry may encourage the reduction of carbon stocks over time to restore forest health and reduce the risk of catastrophic wildfire. Drier, fire-prone forests across the western US are a clear example where reductions in carbon stocks should be interpreted within the context of climatic risk and vulnerability. These same regions and forest types are also often where wood processing infrastructure has been dwindling, and where market access and increased demand for forest products are critical enabling conditions for improved forest management and restoration.
The carbon intensity of timber production is best viewed as an emergent property of a forest management system that accumulates through numerous interventions across a managed landscape over time. This approach is designed to characterize carbon impacts of a forest management system rather than to characterize impacts of a specific timber harvest. Calculations of carbon stock change factors should generally encompass all working forest areas controlled by a timberland owner or type of landowner in a particular timber supply area, not to individual harvest areas or cut blocks.
Thus, a timber supply area where this type of analysis is applied should include areas that are regrowing from previous harvests, areas that are expected to be harvested in the future, and areas where management may be limited or constrained as part of best management practices(e.g., riparian management zones, steep and erodible slopes, or areas of high conservation value within an actively managed landscape). This type of analysis should not include areas that are permanently reserved from timber harvesting (e.g., wilderness areas or parks).
Companies motivated to procure climate smart wood (CSW) are often also interested in carbon offset credits. What is their relationship?
Carbon credits are earned through a verification process for projects that reduce, remove, or avoid carbon dioxide emissions from the atmosphere. Credits earned are listed in a registry where companies who wish to offset emissions can buy them to offset their emissions and meet jurisdictional or corporate greenhouse gas reduction targets. There are two types of markets for carbon offsets: regulatory or compliance markets are established and regulated by governments and operate on a mandatory basis, while non-regulatory voluntary carbon markets are not.
Forest carbon offset projects are one way to earn carbon credits. The degree of rigor of carbon offset projects is variable. Forest carbon offsets have faced criticism related to credibility, additionality concerns, and environmental justice issues, including providing a pathway for greenhouse gas emitters to continue to pollute.
The primary forest carbon offset project types are reforestation, avoided conversion, and improved forest management. For the latter, measurement and verification protocols are applied to forestry operations to determine if their management practices result in “additionality” — that is, higher levels of carbon storage and sequestration than would occur in forests managed at the regulatory floor. An important benefit of forest carbon offset projects is the provision of financial incentives for landowners to implement forest management practices that result in additionality and often increase ecological resistance and resilience in the face of a changing climate. In short, registered forest carbon projects that have earned credits for improved forest management can generally be assumed to be practicing CSF and sourcing wood from them can be one pathway to climate-smart procurement under Option 2 (Intentional Sourcing From Climate Smart Forestry Operations). Because they also provide credible forest-level carbon data, they also have a built-in mechanism for transparency.
In contrast, CSW procurement leverages purchasing power to promote supply chain transparency and CSF management practices, creating a direct link between wood used in a project and climate impacts. These market signals in the building sector supply chain are necessary to transform wood supply chains, and therefore expectations related to the management of forests.
For these reasons, though purchasing carbon offsets and CSW procurement can be complementary, the former is not a replacement for the latter and carbon offsets are not presented as a procurement option in CSWG’s guidance. Prioritizing CSW procurement for building projects or within a company’s supply chain can decrease the direct impact of sourcing and promote climate adaptation and mitigation in forests of origin. These efforts can lower the carbon footprint of a building that uses wood in its construction, but the larger project will generally still produce net carbon emissions. A company could subsequently choose to offset remaining carbon emissions by purchasing carbon offset credits at the level of a project and/or a company’s operations.
For more information contact the Climate Smart Wood Group at info@climatesmartwood.net.
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