The BBC’s article, “Could Wooden Buildings be a Solution to Climate Change?” looks not only at the carbon content of mass timbers such as cross-laminated timbers, but also at CO2 in forests. Some bloggers here will disagree with the author’s assertions. In my view, we have in mass timber structures a means of addressing the apparent increase in mortality in western US forests, including the iconic Douglas-fir: More mortality means more GHGs are released via decomposition and wildfire. Instead of leaving dead trees where they are, we ought to use some of them (not all dead and dying trees, of course, and not from reserved areas, but in areas on National Forests and elsewhere where harvesting is allowed) to produce CLTs, etc., which leads to a reduction in the use of steel and concrete, the world’s two largest sources of GHGs. In stands where mortality is low, but likely to increase, active forest management would both prevent or delay mortality and provide raw materials for mass timbers.
Here’s an excerpt from the article. Read on….
Recently there have been calls for tree planting on a colossal scale to capture CO2 and curb climate change. However, whilst young trees are efficient and effective carbon sinks, the same is not so true for mature trees. The Earth maintains a balanced carbon cycle – trees (along with all other plants and animals) grow using carbon, they fall and die, and release that carbon again. That balance was knocked out of kilter when humans discovered ancient stores of carbon in the form of coal and oil, which had been captured during previous carbon cycles, and began burning them, releasing the resulting CO2 into our atmosphere far faster than the current cycle can deal with.
Many pine trees in managed forests, such as the European spruce, take roughly 80 years to reach maturity, being net absorbers of carbon during those years of growth – but once they reach maturity, they shed roughly as much carbon through the decomposition of needles and fallen branches as they absorb. As was the case in Austria in the 1990s, plummeting demand for paper and wood saw huge swathes of managed forests globally fall into disuse. Rather than return to pristine wilderness, these monocrops cover forest floors in acidic pine needles and dead branches. Canada’s great forests for example have actually emitted more carbon than they absorb since 2001, thanks to mature trees no longer being actively felled.
Arguably, the best form of carbon sequestration is to chop down trees: to restore our sustainable, managed forests, and use the resulting wood as a building material. Managed forests certified by the Forest Stewardship Council (FSC) typically plant two to three trees for every tree felled – meaning the more demand there is for wood, the greater the growth in both forest cover and CO2-hungry young trees.