Permanence calculator

The effects of CO₂ emissions last for hundreds to thousands of years. The permanence of CO₂ removal differs across methods, ranging from temporary (e.g. forests, soil) to effectively permanent (e.g. mineralization, geological). This calculator estimates the upfront costs needed to make a temporary carbon removal strategy permanent over time. Read more in our article.

How to compare the long-term cost of temporary and permanent carbon removal
If a temporary project now costs...
per tCO₂
you actually need to budget...
per tCO₂
for permanent carbon removal.
project duration
How long does a single temporary project last?
switching time
When do we switch from paying for repeated, temporary projects to paying once for permanent storage?
discount rate
What is the rate for discounting future costs? Higher discount rates reduce total costs.
project risk
What is the risk each year that a temporary project fails? Project failure triggers paying for a new project.
per year
temporary cost
What is the cost of temporary carbon removal over time?
$/tCO₂ (initial)
permanent cost
What is the cost of permanent carbon removal over time?
$/tCO₂ (switch time)


We model a decision-maker seeking to achieve permanent climate benefits, whether by paying directly for permanent CO₂ removal or by sequentially renewing temporary carbon removal projects over a 1000-year period. We assume that temporary projects are renewed at the end of each project period. At any point, the decision-maker can switch to a permanent carbon removal alternative and stop purchasing renewals (or never, if this option is turned off).

If project risk is greater than 0%, each project has a probability of failing each year according to an independent Bernoulli trial, and in the event of a failure, another temporary project is immediately purchased.

We calculate the amount that must be budgeted to sustain the temporary removals over time, including the cost of the eventual permanent solution if and whenever the switch is made. All future costs are discounted using the specified discount rate and reported in net present value terms to compare with the upfront cost of the temporary carbon removal project. The model is deterministic except for the stochastic project failure. For every parameter setting, we run the model 50 times and report the mean and standard deviation.

For more details, read our article on this calculator.


This work was generously funded by the ClimateWorks Foundation.

CarbonPlan is a registered nonprofit public benefit corporation in California with 501(c)(3) status.