Carbon Sequestration and Storage in the Built Environment

The authors screened more than 3,000 publications from 2010 to mid-2020 and analysed 180 of them in depth. They look at two mechanisms: photosynthesis in biobased materials such as timber, and carbonation in cementitious materials such as concrete. They also compare the accounting methods used to credit stored carbon, from static life cycle assessment to dynamic approaches that capture when carbon is taken up and released.

What the review finds

• Less than one year of fossil emissions. Most studies find cumulative storage effects in durable products and buildings below the fossil emissions of a single year, ranging from negligible to 175 %.
• The method decides the result. Depending on the accounting method, the same building result of about 1,000 kg CO₂eq/m² can range from −300 to 1,750 kg CO₂eq/m².
• Timber performs well at building level. Timber structures generally show a lower climate impact than comparable buildings in concrete or steel.
• The forest has to be counted. Storage gains in buildings can be offset by carbon losses in the forest, and substitution benefits are sometimes overstated.
• Concrete takes up carbon too, on a smaller scale. Through carbonation, concrete re-absorbs part of its process emissions over its life. In some studies this reaches around a fifth of the initial emissions.

Recent figures for Switzerland come from two studies by ETH Zurich and HES-SO. Potential for biogenic carbon storage towards a net-zero built environment in Switzerland

Potential contribution of biogenic materials in new and renovated buildings towards carbon budgets and storage in Switzerland

Full reference: Arehart, J. H., Hart, J., Pomponi, F., & D'Amico, B. (2021). Carbon sequestration and storage in the built environment. Sustainable Production and Consumption, 27, 1047–1063.