Assessing Temporary Carbon Storage in Life Cycle Assessment and ...

instantaneous impacts. In LCA, some impact categories are covered by multiple indicators at the
midpoint level (e.g. human toxicity uses both cancer and non-cancer effects). For including
temperature increase and rate of change, extensive work is still needed, although it would be promising
and should be investigated further.
2.3 Benefits of temporary carbon storage
In his presentation (see Section 6.5), Marland gave environmental and economic arguments in favour
of temporary carbon storage: it buys time for technological progress and learning, it postpones climate
change, some temporary sequestration may become permanent, sequestering carbon keeps us on a
lower carbon path and mediates the approach of tipping points, etc. There is also an economic
argument which states that temporary carbon storage has value as long as carbon emissions have a
monetary value, whether this value is related to a cap-and-trade system, a carbon tax, or emission
permits. An analogy was developed with the life insurance industry to show that the expected life time
of temporary storage can be described in probabilistic terms, in order to give it a financial value, which
could be used to determine the cost of the temporary credits. Credits for permanent storage could be
bought and sold, and credits for temporary storage could be rented.
2.4 Do temporary carbon storage and delayed emissions matter?
When assessing temporary carbon storage, a time frame needs to be defined, since there is no benefit
for it on an infinite time basis. If the time frame is 100 years, storing carbon for a few years is
important, but if the time frame is much longer, it becomes insignificant. Kirschbaum presented three
types of impact related to global warming: i) the instantaneous temperature increase, which leads to
extreme weather conditions and diseases, ii) the rate of temperature increase, which has an impact on
ecological adaptation, and iii) cumulative heating or radiative forcing, which impacts on long-term
effects such as sea level rise. Storing carbon for a few years and releasing it back to the atmosphere has
two consequences: it decreases the cumulative heating of the atmosphere over a defined time frame,
and it increases the temperature at a given time in the short term. With a longer time horizon, both
effects would become less significant. It is important to determine whether impacts occurring in the
short-term are more important than those occurring in the long-term.
The carbon cycle is dynamic. Taking carbon out of the atmosphere has consequences on the carbon
flows elsewhere in the cycle, e.g. ocean uptake. Releasing one tonne of carbon to the atmosphere or
storing it for a period of time and releasing it later would lead to different CO 2 concentrations at a
given time in the future. It would lead to the same concentration for an infinite time frame, but the
trajectories to that point there would be different, so the timing of the emissions matters with finite
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