I often hear critics dismiss CDR approaches as both too expensive and too small-scale to have a material impact on mitigating climate change. And while that assessment may be true today, many experts predict that, in the long run, CDR will be both affordable and available at a gigatonne (billion tonne) scale.
Consider the following very rough estimate of a supply curve for CDR approaches. This curve is derived from cost and supply estimates from the latest UN IPCC climate change report and from meta-analyses of the scientific literature on CDR (using midpoint estimates where cost/supply ranges were presented) performed by the Virgin Earth Challenge (VEC) team:
The key takeaways from this graph include:
- No single approach is likely to provide all necessary GGR at scale: we will need a basket of CDR approaches to get to the 10+ Gt level of removal that looks increasing required by end of the century in order to prevent significant climate change.
- Many of the technologies with the biggest potential for scale currently cost the most, suggesting that higher carbon prices and/or considerable technology innovation will be key for the adoption of technologies with the potential to remove gigatonnes of CO2.
- GGR isn’t prohibitively expensive at the scale needed to mitigate climate change – estimates suggest a small fraction of global GDP could fund >10 Gt of GGR/yr
- Direct Air Capture (DAC) and enhanced weathering systems are considered in the literature to have effectively ‘limitless’ scale potential. Because of this potential scale, cost-effective DAC / enhanced weathering systems could provide backstop prices for carbon markets.
It is important to emphasize again that this supply curve is just an estimate that is likely to change considerably over the next decades as CDR science and technology advance. Because so many of these approaches are just beginning their development/commercialization pathways today, true costs of CDR approaches vary widely (for e.g., DAC ranging from $40-$2,000/t). Because the confidence intervals surrounding these cost/supply estimates are so large, the ultimate position of different CDR approaches in the supply stack is likely to look different from the positioning in the above chart.
Other key caveats to this curve include:
- Many of these approaches are likely to vary in cost depending on geography.
- Gigatonne-scale biological approaches are likely to compete with each other (and other markets that rely on land as a key input (like food production), likely limiting overall CDR supply. As a result, the sustainable supply of a portfolio of CDR approaches could be considerably smaller than the estimates for each of the individual technologies compiled above.
- If we (very) aggressively cut GHG emissions over the next decades, we can obviate the need for large-scale CDR altogether.