Are you new to life cycle modeling? Does your production stream create waste at any point? In this article, you will learn how to identify and record both waste and by-products in your life cycle assessment (LCA). Accurately tracking these outputs ensures your environmental impact results are precise and compliant with industry standards. This process helps you identify efficiency gaps in your production and simplifies your sustainability reporting.
In this article, you will learn how to:
Distinguish between waste and by-products.
Categorize supplier versus production waste.
Calculate the environmental impact of disposal.
Handle recycled materials and internal loops.
1. Distinguish your outputs
Before entering data, you must determine if your secondary material is Waste or a By-product. The distinction depends on economic value.
The association with waste and its definition in daily life can differ from how 'waste' is defined in LCA. What in the real world you might consider to be waste, can in fact in LCA be a by-product. The rule of thumb in LCA to determine whether something is waste or not is to determine whether your 'waste' has economic value.
Waste: Material with no economic value. You usually give it away for free, or even pay to have it removed or treated.
By-product: Material that is not your primary product but has economic value and can be sold (e.g., selling fruit peels to an animal feed processor).
Example: If you compost a material instead of selling it, it is technically "Waste" because it generated no revenue for your company.
2. Categorize your waste
Identify where the waste enters your system to ensure you aren't double-counting or missing impacts.
Inbound packaging from suppliers
Packaging used by suppliers to deliver raw materials or components to your manufacturing facility should be included in the assessment where it is single-use and disposed of on site. These impacts are considered part of the upstream supply chain and are reported within the production and transport modules relevant to the LCIA method you’re using.
Reusable inbound packaging is treated separately using a reuse allocation approach, as described below, and is not excluded from the assessment solely on the basis of being returned or recycled.
Reusable/Returnable packaging
Reusable and returnable packaging (e.g. pallets, crates, racks) is modeled using a reuse allocation approach. The environmental impacts associated with the production of reusable packaging are allocated per use based on an assumed number of reuse cycles. The assessed product system includes only the share of packaging production impacts attributable to the use required to deliver materials to the manufacturing facility.
Transport impacts associated with the delivery of goods to the facility are included in the assessment. Where return transport of empty packaging is required or arranged by the manufacturer, these impacts should also be included. Impacts associated with repair, refurbishment, or cleaning of reusable packaging are included only where such activities are operated or contractually controlled by your operations.
End-of-life treatment of reusable packaging, including recycling and disposal, is modeled only where you own or control the packaging system. Where reusable packaging is owned and managed by suppliers or third-party pooling systems, end-of-life impacts and potential benefits beyond the system boundary (Module D) are excluded from the manufacturer’s product system.
Outbound packaging to (downstream) customers
Packaging used to ship finished products to customers is included in the product system. The production of packaging materials is reported as part of the Raw Material Supply (A1 in EN15804+A2 for example) stage, while transport to customers and any return transport are reported in the relevant transport modules (A4).
Where packaging is reusable and returned to the manufacturer, impacts are allocated per use based on the expected number of reuse cycles. Where packaging is retained and disposed of by the customer, its end-of-life is outside the manufacturer’s control and is excluded from the assessment unless otherwise required by the applicable program rules.
Product End-of-Life Waste
Once your product in question is shipped out to customers, it is used and then ultimately treated at the end of its life once it no longer serves its purpose. This is when your product itself gets disassembled, and either removed from society (through landfill or incineration), or processed in such a way that the materials the product was made of can be used in a new, next life cycle. The impact from the final disposal of your product must also be accounted for as that's part of the burden associated with creating your product.
3. Calculate production waste impact
To find the total impact of your waste, use this formula:
Total Impact = Amount of Waste x (transport impact to disposal site + disposal method impact)
Figure 1: Understanding waste impact calculations
There are (mostly) four types of waste processing:
Landfill
Incineration
Recycling
Reuse
Each of these cases have their own environmental impacts associated and their impacts depend on the Product Category Rule (PCR) you’re following, which database you're sourcing from, and what countries are involved in your production and distribution.
How to handle missing data:
Transport distance: Check your PCR for "standard values." If none exist, use a best-estimate distance for your local region. e.g. In the Netherlands, according to the Bepalingsmethode, the default travel distance for incinerating waste is 150km.
Disposal method: Some specific LCA methods prescribe recommended end-of-life waste processing methods for specific material types. See this document from the NMD Bepalingsmethode, as an example. If something similar isn't available for your use case, research common local practices (e.g. what percentage of plastic is incinerated vs. landfilled in your country). Googling and using and documenting reliable sources is recommended.
No data available: Select a "market for waste" dataset type in the software for that specific material.
4. Record recycled materials
Recycling impacts depend on where the processing happens.
External recycling: You must account for all impacts (transport and sorting) until the material reaches a state where it has economic value again - the 'end of waste point'.
Internal recycling (used in a different product): Treat this the same as external recycling. Follow the material until it is ready for the second product.
Internal recycling (closed loop): If you feed scrap directly back into the same machine, simply record the net raw material used.
Example - Internal recycling: If you start with 1.05kg of plastic but 0.05kg is fed back into the machine, enter the net 1kg as your raw material input.
Figure 2: Understanding the difference between waste and a by-product.
5. Allocate impact for by-products
Because by-products have value, they share a portion of the total production footprint. You must "allocate" or split the total impact of the modeled system between your main product and the by-product. Read more about allocation here.
Consult your PCR: This is the rulebook for your industry. It will tell you how to split the impact.
Economic allocation: This is the most common method. If your by-product accounts for 10% of your total revenue, it may be assigned 10% of the production emissions.
Figure 3: Calculation emission allocation
Tip - Find the right datasets: When searching the database for waste processes, use the following keywords to find accurate matches:
"Treatment" or "Waste"
"Landfill" or "Incineration"
"Recycling" or "Sorting" (Best for metals and glass)
Next Steps
After correctly accounting for waste, you can also make sure you've correctly accounted for other aspects of your product system.
Check out this article on biogenic carbon calculation
And this one on dataset selection