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Abstract:
Climate stabilization is crucial for restabilizing the Earth system but should not undermine
biosphere integrity, a second pillar of Earth system functioning. This is of particular con-
cern if it is to be achieved through biomass-based negative emission (NE) technologies that
compete for land with food production and ecosystem protection. We assess the NE con-
tribution of land- and calorie-neutral pyrogenic carbon capture and storage (LCN-PyCCS)
facilitated by biochar-based fertilization, which sequesters carbon and reduces land demand
by increasing crop yields. Applying the global biosphere model LPJmL with an enhanced
representation of fast-growing species for PyCCS feedstock production, we calculated a
land-neutral global NE potential of 0.20–1.10 GtCO2 year−1 assuming 74% of the biochar
carbon remaining in the soil after 100 years (for + 10% yield increase; no potential for +
5%; 0.61–1.88 GtCO 2 year−1 for + 15%). The potential is primarily driven by the achiev-
able yield increase and the management intensity of the biomass producing systems. NE
production is estimated to be enhanced by + 200–270% if management intensity increases
from a marginal to a moderate level. Furthermore, our results show sensitivity to process-
specific biochar yields and carbon contents, producing a difference of + 40–75% between
conservative assumptions and an optimized setting. Despite these challenges for making
world-wide assumptions on LCN-PyCCS systems in modeling, our findings point to dis-
crepancies between the large NE volumes calculated in demand-driven and economically
optimized mitigation scenarios and the potentials from analyses focusing on supply-driven
approaches that meet environmental and socioeconomic preconditions as delivered by LCN-PyCCS.
