Greenhouse gas emissions
from building constructioni.e.,
the embodied carbon in buildingsare a significant and growing
contributor to the climate crisis. However, our understanding of how
to decarbonize building construction remains limited. This study shows
that net-zero embodied carbon in buildings is achievable across Japan
by 2050 using currently available technologies: decarbonized electricity
supply, low-carbon steel, low-carbon concrete, increased timber structures,
optimized design, and enhanced building lifespan. The largest emissions
savings would come from increased use of timber structures, with annual
savings of up to ∼35% by 2050, even in cases where timber replaces
low-carbon steel and concrete. Moreover, we show that an expanded
domestic timber supply, coupled with responsible reforestation, could
improve forest carbon uptake by up to ∼60% compared to the
business-as-usual scenario, without the need to increase forest area.
This is achieved through a forest-city carbon cycle that transfers
carbon stocks of mature trees to cities as building materials and
rejuvenates forests through reforestation. Collectively, our analysis
demonstrates that the decarbonization of building construction depends
not on future technological innovation, but rather on how we design
and use buildings with the options we already have.