Carbon Removal Overview

Net zero requires not just reducing emissions but actively removing CO2 from the atmosphere. Every IPCC pathway to 1.5C includes billions of tonnes of annual carbon removal by mid-century. The question is which removal methods can scale, and whether betting on future removal justifies slower emission reductions today.

Carbon removal falls into two categories. Nature-based: afforestation (planting trees), soil carbon management, ocean-based approaches. These are cheap ($5-50/tonne) but face permanence issues (trees burn, soil carbon reverses with land use changes) and land competition. Engineered: direct air capture (DAC) with geological storage, enhanced weathering, bioenergy with carbon capture (BECCS). These are expensive ($100-600/tonne) but offer more permanent storage.

The scale gap. Current removal capacity is roughly 2 Gt CO2/year, almost entirely from existing forests. IPCC scenarios require 5-10 Gt CO2/year by 2050, and engineered removal is a rounding error today: DAC removes about 0.01 Mt CO2/year, a factor of 500,000 below what the scenarios assume.

Can nature-based removal simply scale up to fill the gap, since it is 10-100x cheaper?

Permanence is the catch. A forest stores carbon only as long as it stands; fire, disease, or a change in land ownership can reverse decades of storage in a season. Engineered removal with geological storage is effectively permanent but costs $100-600/tonne. The portfolio problem is buying cheap, reversible storage and expensive, permanent storage in the right proportions, while never letting either substitute for cutting emissions in the first place.

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