|Aspect||G- 18 Allocation case for cement-based materials|
||Increasing numbers of building products are being made of secondary raw materials (SRM), or of generated waste that can be recycled throughout their life cycle. On the one hand, recycling eliminates the need to use virgin raw materials. On the other hand, the new commercial interest in waste can be seen as a shift in their status from waste to co-product.Several industries use a considerable amount of waste produced in other economic sectors (e.g. the cement industry uses blast furnace slag from the steel industry, and fly ash from electricity production). Depending on the ‘end of waste‘ status of each product, allocation rules may be needed to separate the burdens between the producer of the waste and the user. The environmental impact of very common building materials can thus vary greatly, depending on the allocation rules chosen. How can this critical allocation case be treated, e.g. for the use of waste in the cement and concrete materials?|
related study objective
|☒ stand-alone LCA||☒ comparative assertion|
related study phase
|goal and scope definition||inventory analysis (LCI)||impact assessment (LCIA)||interpretation||reporting|
|new buildings||existing buildings||construction products||screening LCA||simplified LCA||complete LCA|
|Provisions||The allocation rules should comply with EN 15804 and EN 15978. In addition, the rules of national EPD programmes should be followed (if available).|
||Generally speaking, the allocation rules should be defined in every national context, together with the relevant sectors that use and produce the waste or co-product).A manufacturer of building products using e.g. wastes from another economic sector needs to share burdens with the first user. The allocation actually depends on the ‘end-of-waste’ status: that is, whether the waste is treated as waste (treatment allocated to the first user, and reported in Module C) or whether it is treated as a new product (when end-of-waste status is reached, the waste is transformed into a product, and the processing is allocated to the new product life cycle).
One option is to look at the market value of the waste, as proposed in the ILCD Handbook (see reference above). For example, waste from the steel industry (blast furnace slag) or from electricity production (e.g. fly ash) may be used to produce cement with a low clinker content.
Current practice in Europe shows varying rules for the allocation of cement SRM. They are treated as co-products in the UK (and in the subsequent EPDs), whereas they are considered as waste in France and in Germany (and in the subsequent EPDs of these two countries). The new European Waste Directive (see below) is currently not being applied in a consistent way.
The practitioner, when using LCA data that may be sensitive to the allocation of by-products according to the EU Directive (considered either as waste or as co-product), should specify the allocation rules, especially for complete LCA. Sensitivity analysis should be conducted if the allocation of by-products has a significant role in the LCA results.
A third guidance point concerns the use of background data. Depending on the type of background data, they may not comply with the allocation rules. As the practitioner does not have an influence on the background data, the best recommendation is to be transparent, e.g. in the LCA methodological report.
Further information and references on this issue: