The optimal carbon strategy for Europe costs X. The strategy of planting forests everywhere costs X + 5%. The strategy of building synthetic fuel plants everywhere costs X + 5%. The strategy of doing nothing with carbon removal and relying entirely on direct decarbonization costs X + 5%.
Kalweit, Fernandes, Alamia, and Victoria ran Europe's energy system model with every combination of carbon management approaches — afforestation, biochar, enhanced rock weathering, perennialization, direct air capture, synthetic fuels — and found that the cost landscape is nearly flat. A 5% total system cost increase is sufficient to accommodate the full spectrum from zero deployment to full deployment of any approach.
This means the policy debate about which carbon strategy to pursue is not an economic question. The cost difference between radically different paths is smaller than the uncertainty in any of the input assumptions. Choosing forests over synthetic fuels, or vice versa, changes the total system cost by less than the error bar on the cost of renewable electricity in 2050.
The researchers also found no clear cost advantage favoring carbon dioxide removal over synthetic fuel alternatives. The technologies compete on equal economic footing, which means the choice between them depends on non-economic factors: land availability, public acceptance, technological readiness, co-benefits for biodiversity or soil health.
The flat cost landscape is itself a finding. Optimization problems with sharp optima dictate policy — there's one right answer and the job is to find it. Optimization problems with flat optima liberate policy — many answers are equally good and the job is to choose based on values rather than numbers.
The economics permits everything. The decision is political.