G-16 (Buildings) / G-15 (Products) Accounting for carbon storage/carbon sequestration

Aspect G-16 (Buildings) / G-15 (Products) Accounting for carbon storage/carbon sequestration
Description
Some products (e.g. wooden products) take up atmospheric carbon dioxide while producing biomass. Concrete- and lime-based products can also take up atmospheric carbon dioxide through recarbonization during the use phase . By using these materials or products, this fixed CO2 is stored during the service life of the product. It is then released during combustion processes, or in landfill during full or partial decay of the biomass, as either CO2 or methane, which itself may be captured to produce CO2. Owing to the storage of carbon of biogenic origin in some products during the use of these materials, the CO2 stored is not released in today’s ecosphere but at some future date. Usually, 100-year assessment periods for the fate of greenhouse gases are taken into account in LCA studies (use of the indicator global warming potential, GWP100), but, depending on the case, this period can be insufficient to counteract the storage period.In this case, how should the biogenic carbon be taken into account? Should this temporary storage effect be accounted for? Also, the matter of sequestration of carbon in soils and organic matter due to land-use changes is frequently discussed. How should this aspect be treated?

related study objective

stand-alone LCA comparative assertion

related study phase

goal and scope definition inventory analysis (LCI) impact assessment (LCIA) interpretation reporting

relevant for

new buildings existing buildings building products screening LCA simplified LCA complete LCA
Provisions As a conservative approach, the storage or sequestration of biogenic carbon as an additional benefit should not be accounted for, as this is a temporary effect. All greenhouse-gas-related environmental impacts should be quantified solely with the use of IPCC’s GWP-100 impact category. This means that the uptake of carbon dioxide into biomass is considered in the inputs to biomass production, and the emissions of biogenic carbon (as carbon dioxide or methane) are considered in the outputs.
Rules from

ILCD

 

Provisions 7.4.3.7 Future processes and elementary flows
Citation from provisions 7.4.3.7:
“VII) SHALL – Inventory temporary carbon storage and delayed GHG emissions: only if temporary carbon storage in bio-based goods is considered […] delayed emission as CO2 or CH4 shall be modelled analogously to delayed emissions of fossil carbon dioxide and other greenhouse gases” Additional citation from the ILCD Handbook:The uptake of “carbon dioxide” by plants shall be inventoried under “resources from air”. This applies to all photosynthetic organisms.

The ILCD Handbook recommends that for better methodological clarity and flexibility, as well as easier communication, the release of carbon dioxide and methane be additionally differentiated between fossil and biological sources. Both the uptake of carbon dioxide from the atmosphere and the release of both fossil and biogenic carbon dioxide are assigned characterization factors for the impact assessment. The full provision for inventory of temporary carbon storage and delayed GHG emissions can be found in the ILCD Handbook.

Guidance
This aspect is under intense discussion within various organizations. Different perceptions exist, and various documents propose different solutions to this question. For example, some documents define ‘discounts’ for the temporal storage of carbon in products. Others suggest, for example, reduction factors to be applied to GWP results for a temporal sequestration of carbon in soil and organic matter due to land-use change.In order to be flexible concerning future development of and consensus-building on this aspect, it is helpful to track carbon with a distinction made between biogenic and fossil sources. For example, in the background LCI databases, it is likely that elementary flows will be found such as:Resources: ‘carbon dioxide (resource), in air’Air emissions: ‘carbon dioxide (fossil), in air’ and‘carbon dioxide (biogenic), in air’.This is also valid for methane and carbon monoxide.Further information can be found in the following sources:

  • ISO working group on carbon footprint;
  • PAS 2050.
  • Standard in preparation in CEN TC 175 prEN 16449: ‘Wood and wood-based products – Calculation of sequestration of atmospheric carbon dioxide’ (status: under approval)

The treatment of biomass at the end of life is covered in the aspects of Module C and this should be considered alongside this guidance.


Comments are closed.