Our paper on biogenic carbon storage in global urban building stocks is out in Environmental Research Letters, led by Alessio Mastrucci at IIASA and written with colleagues at TU Graz and six other institutions.
The question behind it: bio-based materials hold carbon inside a building for as long as the building stands, and that is often offered on its own as a reason to build with them. Storage is not the same as mitigation, though, and neither is the same as something the world can supply. This paper separates the three, across global urban building stocks from 2020 to 2100, at substitution levels of 10%, 30% and 50%.
What it finds:
- Structural wood stores 11.0 to 24.8 GtCO₂eq by 2100, and cuts cumulative net embodied emissions by 20 to 100 GtCO₂eq, a reduction of 8% to 40% against current construction practice.
- Biochar-based concrete does considerably less: 7.9 to 14.5 GtCO₂eq stored, and up to 4% off net embodied emissions. Only so much cement can be replaced before structural performance suffers, and that ceiling is the limit, not the ambition.
- Sufficiency and circularity multiply both. Less floor area per person, longer building lifetimes, lighter structures, reuse and recycling: combined with wood, these take cumulative net embodied emissions down by up to 64%, and with biochar by up to 41%.
The finding worth carrying out of it is the last one, and it is not the arithmetic. Reaching the full storage potential through material substitution alone would need a substantial expansion of biochar supply, and for wood it depends strongly on how far substitution actually goes. Demand-side measures are not a supplement to the material switch. They are what brings it within reach.
That is the same argument this institute makes about the building stock generally, arrived at here from the material side: what is physically possible and what is available at scale are different questions, and only the second one decides anything.
Read the paper, which is open access, or see it in our publications.