A-01 Distinction between wastes and by-products during the extraction and the processing stages

Aspect A-01 Distinction between wastes and by-products during the extraction and the processing stages
Several wastes and by-products are either used or generated during the production phase of building products. A waste is an output from a process that has not yet reached the end-of-waste state. A by-product is an output that is not a waste, but has low value relative to the product or co-products.How should wastes and by-products be handled? Should energy consumption for waste disposal be included? Should processing energy/water and capital equipment/machinery required for waste disposal be included? How should allocation and crediting issues be handled?

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 construction products screening LCA simplified LCA complete LCA
Provisions If the goal of the study is to make an EPD, the rules provided by EN 15804 should be followed. This will increase consistency with other studies and with EN 15804-based EPDs.For other goal definitions (other than for EPD), ILCD and EN 15804 should be analysed and the most relevant rules should be selected.
Rules from:

EN 15804

6.3.4 System boundaries Product stage

6.4.3 Allocation of input flows and output emissions


Provisions: 7.9.2 Avoiding allocation by subdivision or virtual subdivision
Provisions: 7.9.3 Solving multifunctionality by allocation
The following guidance is relevant where an EPD is required according to EN 15804, or where the best possible consistency with EPDs that follow EN 15804 is desired. This is the agreed standard for providing EPD and LCA information for construction products, and for their use in building-level assessments; any regulation in Europe in this area will follow this standard. If there is no interest in understanding the performance of the product according to EN 15804, other approaches – of ISO 14044 and the ILCD Handbook – can be followed. However, these may lead to different results.According to EN 15804, the impacts associated with waste treatment and disposal of wastes are included in the system boundary until the end-of-waste status is achieved.As stated in G-16 Allocation, according to ISO 14040/14044, the ILCD Handbook and the EN 15804 standards, when dealing with systems involving multiple products and recycling processes, allocation should be avoided as far as possible; when unavoidable, allocation should be considered carefully, and should be justified.Allocation cannot be avoided in situations where processes cannot be subdivided and it is impossible to make one product without the other co-products, by-products or wastes.Allocation has to be handled as described in EN 15804, EN 15978 and the ILCD Handbook.

A waste may therefore become a by-product or co-product (with higher value) from the process at the system boundary, and can therefore be considered in terms of co-product allocation according to EN 15804 (see, which states: “Flows leaving the system at the end-of-waste boundary of the product stage (A1–A3) shall be allocated as co-products. Loads and benefits from allocated co-products shall not be declared in Module D (see If such a co-product allocation is not possible, other methods may be chosen and shall be justified. Therefore, as a general rule, potential loads or benefits from A1-A3 do not appear in module D.”

EN 15804 does not include the second option for avoiding allocation provided within ISO 14044, “expanding the product system to include the additional functions related to the co-products” (often known as system expansion), but does provide that any use of upstream data that does not respect the allocation principles in EN 15804 “shall be clearly stated and justified in the project report. These data shall be in line with EN ISO 14044 allocation rules.” The basic procedures and assumptions for co-product allocation used in EN ISO 14044 have been refined in EN 15804 to reflect the goal and scope of EN 15804 and EN 15643-2. This is because EN 15804 covers all construction products, and in many cases construction products use co-products, by-products and wastes in their manufacture, as well as producing them during manufacture, construction and at end of life. In this situation, where there is such interdependence, it is not possible to use the process of system expansion, as the impact both of the product and co-products and of recycled wastes is required to provide input data for the product LCA study, not just the impacts of the main product of a process.  EN 15804 also requires, in 6.4.2, that “the same calculation procedures shall be applied consistently throughout the study,” which means that different allocation procedures should not be applied to one upstream dataset than are used for other co-products entering or leaving the system boundary.

Where possible, if there is more than one output from a system, the system should be broken down until the system studied is producing only one output. This is the case where a factory produces two separate products on two production lines – here submetering or other mechanisms such as monitoring should be used to split the inputs and outputs of the system between the two production lines.

However, there are many situations where a system produces two or more outputs. For example, the production of cut stone always results in the production of broken stones and dust; and the production of sawn timber always results in the production of sawdust, bark and waste timber, which can be chipped.

In these instances, the other outputs can be considered as co-products, by-products or wastes, and the allocation should reflect the main purposes of the process. If the wastes are disposed of, and never reach the end-of-waste state, the impacts of disposal are included within the system boundary. If the wastes, after recycling processes, reach the end-of-waste state, the impacts until they reach this state should be included within the system boundary, and the secondary product produced is considered as a co-product for co-product allocation.

If the co-product or by-products are never considered as waste, then they are both considered for co-product allocation at the point where they leave the system.

If the co-products have a similar value (i.e. the comparable prices per unit are within 25% of each other), then EN 15804 states that the impacts can be allocated on the basis of the physical unit of production.

If the co-product’s value varies by more than 25%, then the co-product allocation should be based on economic value, according to EN 15804. All the outputs at the system boundary (including wastes that have been treated to reach the end-of-waste state) are considered in terms of the percentage of revenue (income) they bring to the system. Comparison of revenue from products should be undertaken using the market value of the normal unit of production (e.g. kg or MJ), based on normal pricing units and long-term averages (3 or 5 years) if prices fluctuate. The impacts of the system are then split between them on the basis of these percentages.

For example, in the case of an iron ore mine that produces iron ore and stone that can be used for aggregate, for each kg of iron ore produced and sold for X per kg to be smelted into iron, there may be T tonnes of stone produced and sold for Y per tonne that can be further crushed and used as aggregate.

The impacts of the iron ore mine extraction system are then split between the co-products as follows:

Revenue from iron ore: 1 kg × X/kg = X

Revenue from stone: T tonnes × Y/tonne = YT

Total revenue/kg iron = X + YT

Proportion of impact allocated to iron ore = X/(X + YT)

Proportion of impact allocated to stone = YT/(X + YT)

Note that this approach to co-products and co-product allocation, provided in EN 15804, is different from that described in the ILCD, where a physical causality is assumed for both the iron ore and the stone, and the impacts of extraction would be allocated between the co-products on the basis of mass.

For both the iron ore and the stone, further processing of the iron ore (smelting of the iron ore) would be completely allocated to the iron, and further processing of the stone (crushing to form aggregate) would be completely allocated to the aggregate.

Where the product studied is of high value, a conservative approach in simplified and screening LCA could be to omit the allocation phase and keep all impacts with the high-value product. Where the product studied is a low-value co-product or by-product, it is important to consider the impacts allocated from the production process, as they may still be significant for the low-value product, even if they are only a very small proportion of the high-value product’s impact.

The market value of co-products may change over time, but it is the relation between them over time that is relevant, not the actual values. The actual overall revenue may be sensitive, but it is the percentage of revenue that is required for allocation. Rather than data for the whole plant, it could be considered at the cost of 1 kWh electricity and the cost of the resulting fuel ash etc. It may be clear, for instance, if the fuel ash is not a waste, that its relative value is less than 1% of the cost of the electricity.

Where co-products have incompatible units, e.g. mass and energy, it is essential to use economic allocation.

Wherever possible, market-value data should be obtained from the supplier of the waste or secondary material, or from a relevant local trade association. In many situations an estimate can be made of the values of the different co- products, goods and services, including waste-processing services, if relative values cannot be obtained from the suppliers. If market prices are not known, there are several reliable sources on many product prices, including historical prices and expected prices in terms of futures. The web is a unique source of price data. Hundreds of websites are available on most commonly traded products. The relevant search term for market price is ‘fob’ (free on board at the location of the supplier, without insurance or transport.) The other price type is ‘cif’, stating a specific place of deliverance: e.g. ‘cif Chicago’ for the price of steel as delivered in Chicago.

Sources of relevant and appropriate data will vary, depending on material and location, and should be considered on a case-specific basis.

Manufacturing waste that is recycled into the same cradle-to-gate process can be considered as closed-loop recycling where there is a matching input, but all impacts must be reported in Modules A1–A3. Where the waste output is not sufficient to match the linked recycled input, then additional upstream data for the recycled input must be used. Where the output is more than sufficient to produce the recycled input, then the additional output flow, at the system boundary (end-of-waste state) should be considered as a co-product for co-product allocation.

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