Temperature Changes Induced by Biogeochemical and Biophysical Effects of Bioenergy Crop Cultivation

The production of bioenergy with carbon capture and storage
(BECCS)
is a pivotal negative emission technology. The cultivation of dedicated
crops for BECCS impacts the temperature through two processes: net
CO2 removal (CDR) from the atmosphere (biogeochemical cooling)
and changes in the local energy balance (biophysical warming or cooling).
Here, we compare the magnitude of these two processes for key grass
and tree species envisioned for large-scale bioenergy crop cultivation,
following economically plausible scenarios using Earth System Models.
By the end of this century, the cumulative CDR from the cultivation
of eucalypt (72–112 Pg C) is larger than that of switchgrass
(34–83 Pg C) because of contrasting contributions of land use
change carbon emissions. The combined biogeochemical and biophysical
effects are cooling (−0.26 to −0.04 °C) at the
global scale, but 13–28% of land areas still have net warming
signals, mainly due to the spatial heterogeneity of the biophysical
effects. Our study shows that the deployment of bioenergy crop cultivation
should not only be guided by the principles of maximizing yield and
CDR but should also take an integrated perspective that includes all
relevant Earth system feedbacks.