Permanence is cheap – is it really too difficult?
The financial implication of repeating the same storage every half century is smaller than you might think.
Once fossil carbon has been allowed to enter the mobile surface carbon pool (i.e., the atmosphere, surface ocean), it will linger there for thousands if not tens of thousands of years causing climate change and ocean acidification (Archer, 2005; Archer et al., 1997). Policies for achieving a “net-zero” carbon budget aim to fix this problem by matching fossil carbon extraction with carbon disposal that can credibly sequester carbon on a similar time scale (Allen et al., 2022). This timescale is referred to as “climate-relevant”.
It is surprisingly difficult to convince policymakers, purveyors of carbon storage, or organizations that certify sequestration of the simple logic of the need for permanence. Some storage operators may feel threatened because they can only offer short-lived storage. There is nothing wrong with temporary carbon storage if it comes with a guarantee that accidental or planned leakage is made up of additional storage, which again might be temporary. However, many policymakers feel that it is unreasonable or politically impractical to place this obligation on storage operators, suggesting that the cost of such a guarantee is too high and would stifle action.
A guarantee of permanence on climate-relevant time scales need not be expensive for most temporary storage that have storage times up to a century. For example, if storage is expected to last fifty years, one only needs to include in the price of storage the purchase of a new certificate in fifty years from now. With a typical discount rate setting aside enough money to repeat the same storage operation every fifty years would raise the cost of storage by less than 10%.
Therefore, guaranteeing permanence should be easy, unless the storage operator judges the cost of liability very differently. There may be many different reasons why storage operators may be hesitant to accept liability. However, these reasons usually disqualify a storage technology as an acceptable means of balancing the carbon budget. Any operator, who is uncertain of the expected storage time or is unable to quantify the amount that is put initially into storage and remains in storage, fails to offer a viable storage option. Furthermore, any storage operator who is unsure that the same method of storage could be repeated in fifty years from now at a similar cost is building a bridge to nowhere and should not be supported.
Carbon storage without such a guarantee pushes the problem to future generations. In effect, purchasing such storage would hoodwink the public into the mistaken belief that carbon has been taken care of, when instead the problem has just been swept under the rug. Unlike greenwashing strategies, credible and accountable methods of storage can easily afford a guarantee of permanence.
In more depth
Assuming an annual discount rate of d and an initial cost of P0, the net present value of purchasing the same sequestration every 50 years is given by
Where α is the factor by which the cost is discounted over 50 years, i.e., α = (1 - d)50. If d = 5%, then α = 0.077. Therefore, P = 1.083 x P0. In other words, the guarantee costs 8.3%.
Works cited
Allen, M.R., Friedlingstein, P., Girardin, C.A.J., Jenkins, S., Malhi, Y., Mitchell-Larson, E., Peters, G.P., Rajamani, L., 2022. Net Zero: Science, Origins, and Implications. Annu. Rev. Environ. Resour. 47, 849–887. https://doi.org/10.1146/annurev-environ-112320-105050
Archer, D., 2005. Fate of fossil fuel CO2 in geologic time. J. Geophys. Res. 110, C09S05. https://doi.org/10.1029/2004JC002625
Archer, D., Kheshgi, H., Maier-Reimer, E., 1997. Multiple timescales for neutralization of fossil fuel CO2. Geophys. Res. Lett. 24, 405–408. https://doi.org/10.1029/97GL00168