Daniel Pike, Principal at RMI leading their Carbon Removal Initiative, explores the range of removal options and differences in what they require to scale.
Scaling carbon removal to meet the demands of the climate crisis is a daunting challenge. But there is good news. There are many approaches – we counted 32 in our new roadmap. They rely on different inputs, can be performed in different locations and benefit from different applications of science and technology. This suggests possibilities for a portfolio of carbon removal solutions, comprised of different approaches in different locations, that is diversified enough to scale.
The best-known approaches are trees and direct air capture (DAC). Trees serve as natural carbon sinks by removing carbon dioxide from the atmosphere through photosynthesis and storing that carbon dioxide as biomass. DAC pulls carbon dioxide out of the air using fans and materials that selectively bind with carbon dioxide.
But there are many other approaches. Carbon dioxide naturally reacts with and is stored by materials that the earth has in abundance, including rocks, water, and a variety of plants besides trees. These reactions can be accelerated in many ways. This is the foundation, for example, for macroalgae or microalgae sinking, terrestrial enhanced weathering, and electrochemical water capture. New approaches and companies are continually emerging, and there is still runway for more innovation.
These approaches rely on different inputs to different extents. Some are more easily and cheaply deployed, but harder to measure. Some are expensive, but highly durable. All may be challenging to scale, depending on the availability and price of their primary inputs: plants, minerals, and low-carbon energy.
We will require the smart and strategic deployment of different approaches to carbon removal in different locations, depending in large part on community preferences and on the land, water resources, low-carbon energy, and infrastructure available. Globally, given the billions of tons needed, we will need a broad portfolio that incubates a range of approaches to mitigate resource constraints, address varied community preferences, and diversify risks.
As carbon removal markets and policy regimes evolve, the rules of the game should be configured to enable discovery, testing, and — if approaches are validated upon testing — scale-up of the full set of potential approaches. We need an open playing field for innovation, with rules flexible enough to maximize the overall level of carbon removal within our resource constraints, and with robust environmental and social safeguards in place. If one approach emerges as dominant, that could put carbon removal on a virtuous cycle of falling costs as production increases – an ideal outcome. But if no technology emerges as dominant, which looks more likely, future generations will thank us for spreading our bets.
Read more: The Applied Innovation Roadmap for CDR, November 2023
