Discussions on reducing buildings’ carbon footprints have become more prominent, especially as more residents and business leaders learn how to make sustainable choices. Biological sources — such as plants, soil and trees — have biogenic carbon footprints. Biogenic carbon gets pulled from the atmosphere as those sources grow.
Calculating the Carbon Storage Balance
When people cut down trees to source wood for construction projects, they must consider the impact caused by that cessation of carbon sequestration potential. Their actions create an associated carbon footprint.
Representatives from Germany’s Institute for Applied Ecology (Oeko-Institut) propose a carbon storage balance method for calculating the effects. It asserts that the timber from felled trees has a corresponding amount of carbon the forest could have stored if people did not take those resources.
Germany uses cubic meters to measure forest volume, and 1 cubic meter equals approximately 35 cubic feet. Calculations indicated that every harvested cubic meter of wood could have held 600 to 1,700 kilograms of carbon dioxide.
One reason for that wide range is that the amount of carbon a tree can store depends on the forest type and wood extraction method. Trees taken from young, healthy forests are more effective at capturing carbon than those sourced from damaged areas.
Another decisive factor is how long the CO2 stays stored in the wood product. It remains there for decades if people use the material for construction projects. People’s use of wood can even out the carbon storage balance if the application curbs or does not contribute to significant fossil fuel-derived carbon emissions.
The organization found that a project’s associated greenhouse gas emissions could be 76% fewer using structural timber instead of mineral-based or fossil fuel-derived alternatives.
People wishing to minimize the source-related carbon footprints of their wood buildings should consider choosing materials from sustainably managed forests. In those cases, stewards maintain the land and its associated ecosystems, reducing the adverse impacts of tree felling.
Assessing Project-Related Specifics
Calculating the carbon footprint of a wood building can begin with analyzing its origins and making strategic decisions to maintain sustainability. People should also investigate opportunities to reduce the carbon footprint of wood buildings with reuse opportunities.
That is especially easy to do with projects that remodel existing structures. If the site already uses wood, could people repurpose it during the updates? Some estimates suggest that over three-quarters of materials present before residential remodels begin could be reused.
Those overseeing wood construction projects must also assess emissions linked to vehicles transporting materials to the site or moving debris away from it. Similarly, do construction crew members primarily drive individual cars to arrive for their shifts, or do they come in groups?
Creating a wood building also involves using various heavy machinery. Fortunately, electric equipment is more widely available, which reduces a project’s associated emissions. Additionally, many machines have connectivity features that display their average daily running time or how many assets are simultaneously operational. Identifying unusual trends may prompt managers to make changes that increase sustainability and shrink the carbon footprint.
Sustainable avenues exist when people keep products out of landfills, too. That is why people often view eco-friendly reclaimed wood as superior to new materials. Additionally, it withstands various climatic environments and temperatures because of its previous exposure to them during earlier usage. That characteristic can support emissions reductions because durability should make the construction efforts last longer before building occupants need repairs or upgrades.
Performing a Life Cycle Assessment
People interested in the carbon footprint of wood buildings can get more in-depth information by performing a life cycle assessment. One such investigation compared the carbon footprint accounting methods used for multi-residential buildings in 16 countries. Those involved uncovered numerous useful takeaways related to structures containing biogenic carbon products.
This study reviewed three specific methodologies for measuring biogenic carbon:
- The 0/0 approach: This approach does not consider the storage or release of carbon emissions.
- The –1/+1 method: This accounts for biogenic carbon trapped during the material’s production and released at the end of its life. However, this measurement option does not calculate the emissions associated with end-of-life treatments for the material.
- The -1/0 method: This considers the impact of sending the wood to a landfill or recycling it once it is no longer useful. The researchers considered landfills and recycling permanent biogenic carbon sinks in these cases.
Additionally, the group clarified that timber sourced from certified forests has no — or negative — CO2 emissions during production as long as people counteract removing those mature trees by planting new ones.
Digging Into the Details
The research centered on a building constructed in 2016 in Quebec, Canada. Although 52% of the structure was 25 MPa concrete, 27% featured softwood beams and other wooden characteristics. Calculations indicated the project required approximately 1,500 metric tons of wood.
Several countries examined in the study use biogenic carbon calculations assuming permanent landfill sequestration. However, significant differences exist. For example, New Zealand calculates 99.9% assumed permanent sequestration of biogenic carbon, but the figure is 90% in Australia. Additionally, Canada’s system stipulates that 11% of the emissions get released after disposal, and the figure is either 8% or 9% in France, depending on the wood type.
Additionally, recycling or reusing the wood at the end of its life could beneficially impact emissions. That is only the case when those disposing of the wood have secured legal commitments that service providers will not release timber products’ biogenic content into the atmosphere. The researchers did not check those obligations but mentioned the need for further research.
Putting It All Together
Becoming familiar with biogenic carbon and the effect of wood construction projects is crucial to verifying sustainable impact.
Although the 16-country investigation highlights the numerous and significant location-based differences in carbon calculations, it also emphasizes the need for people to learn the method used where they plan to build.
An alternative is the more straightforward and universally applicable method described by the Oeko-Institut. People can also align that framework with their project to calculate the potential emissions.
Consider a wood building featuring many reclaimed resources that people plan to use for the foreseeable future. It would have a substantially lower environmental impact than a wooden building with all new materials constructed to use for a very short time, such as as a temporary shelter for music festival attendees.
Industry professionals should continue seeing sustainable building projects as the ideal way forward, but they must evaluate the factors here to calculate the individual impacts of their efforts.
