The potential contribution to climate change mitigation from temporary carbon storage in biomaterials

While lasting mitigation solutions are needed to avoid climate change in the long term, temporary solutions may play a positive role in terms of avoiding certain climatic target levels, for preventing the crossing of critical and perhaps irreversible climatic tipping points. While the potential value of temporary carbon storage in terms of climate change mitigation has been widely discussed, this has not yet been directly coupled to avoiding climatic target levels representing predicted climatic tipping points. This paper provides recommendations on how to model temporary carbon storage in products in life cycle assessment (LCA), in order to include the potential mitigation value relative to crossing critical climatic target levels. Further, estimates are made on potential magnitude of this value, highlighting the importance of including this aspect in climate change impact assessment of biomaterials. The recently developed approach for quantifying the climate tipping potential (CTP) of emissions is used, with some adaption, to account for the value of temporary carbon storage. CTP values for short-, medium- and long-term carbon storage in chosen biomaterials are calculated for two possible future atmospheric greenhouse gas (GHG) concentration development scenarios. The potential magnitude of the temporary carbon storage in biomaterials is estimated by considering the global polymer production being biobased in the future. Both sets of CTP values show the same trend; storage which releases the carbon again before the climatic target level is reached increases the CTP value of the product compared to a situation with no storage of the product, whereas storage extending beyond the time where the climatic target level is predicted to be crossed according to the GHG concentration scenarios contributes with negative CTP values, which means mitigation. The longer the duration of the storage, the larger the mitigation potential. Temporary carbon storage in biomaterials has a potential for contributing to avoid or postpone the crossing of a climatic target level of 450 ppm CO(2)e, depending on GHG concentration development scenario. The potential mitigation value depends on the timing of sequestration and re-emission of CO2. The suggested CTP approach enables inclusion of the potential benefit from temporary carbon storage in the environmental profile of biomaterials. This should be seen as supplement to the long-term climate change impacts given by the global warming potential which does not account for temporary aspects like benefits from non-permanent storage in terms of avoiding a critical climatic target level.