Fig. 7: Heat maps of cost-optimal configurations.

Heat maps of cost-optimal configurations for achieving a net-negative (−110%) emissions target when varying the price of biomass imports (x axis) and DAC capital expenditure (y axis). For comparison between different used metrics in literature: DAC capital costs (CAPEX) of €1,500–7,000 kg⁻¹ CO₂ h⁻¹ correspond to €171–800 t⁻¹ CO₂ per year at a full utilization rate or a capital cost of €16–75 t⁻¹ CO₂ (not including operational expenditure) with a 7% discount rate and a 20-year lifetime. The assumed capital cost of the carbon capture unit for BECC is here assumed at a constant €2,400 kg⁻¹ CO₂ h⁻¹, but it is likely that cost progressions for DAC would spill over also to BECC. a, Total biomass usage. b, Biomass imports. c, The system cost increase of excluding biomass compared to the least-cost solution for all combinations of carbon sequestration capacity and upstream emissions of biomass imports. d–f, BECC (d), DAC (e) and total CC and DAC (f).