What makes carbon removal fit for purpose?

Carbon dioxide removal is necessary to mitigate climate change, but not all methods will be fit-for-purpose. Some can be unethical, unsafe, counterproductive, and ecologically damaging. But, because fitness is a value judgment, it is critical to have a clear definition of its meaning. We propose to define fit-for-purpose as an attribute of a carbon removal method that indicates that its detrimental side effects are sufficiently small to be acceptable. A method is not fit for purpose if it risks unsustainable environmental or societal damages. We then identify six criteria that can be used to judge a method’s fitness-for-purpose based on those chosen by other organizations, including carbon negativity, measurability, additionality, safety, and low environmental risks. We compare our perspectives on these criteria to those presented by six entities including Microsoft, Carbon Direct, Frontier, California’s Air Resources Board, the United Nations Development Program, and the Accountability Framework. This work reflects our thinking in 2023 with some updates in 2024 and intends to be a starting point for a more thorough development process that ought to be adopted by the international carbon removal community in an inclusive process.