Session 2 Q&A
Thanks again for all the great questions, everyone! Just like Session 1, you were incredibly active and we had 184 questions in total across the Q&A panel and the chat.
I narrowed it down to 147 unique, Session-2-specific questions. These reflect everything that was new, technical, or advanced compared to Session 1.
I categorised the questions according to the following topics:
- A1–A3 Manufacturing, Materials & Inventory Modeling
- Energy Use, Electricity Modeling & Renewable Energy
- Transport Modeling (A2 & A4)
- End-of-Life (Module C) & Module D
- Allocation, Recycling & Circularity Rules
- Functional Unit, Declared Unit & Product Modeling Structure
- Data Quality, Sources, Representativeness & Uncertainty
- Software Workflow & Modeling Questions
- Scenario Modeling & Assumptions
- Industry- & Material-Specific Questions
- Interpretation of Results & Impact Categories
- Verification, Documentation & Compliance
- Additional Technical or Edge-Case Questions
1. A1–A3 Manufacturing, Materials & Inventory Modeling
(Questions 1–19)
1. How do I decide which processes to include in A1–A3 for a manufactured product?
A1–A3 should include all processes required to turn raw materials into the finished product as it leaves the factory gate. This covers material extraction, transport to manufacturing, processing, energy use, auxiliary materials, and direct emissions. A good rule of thumb is: if it physically happens before the product leaves the plant, include it.
2. What level of detail is required for modeling production steps in A1–A3?
You need enough detail to represent the main material and energy flows, but you don’t need to model every minute sub-step. Focus on major inputs (materials, fuels, electricity) and significant emissions or waste streams. Small operational details (e.g., minor cleaning or administrative activities) are typically excluded unless they materially affect impacts.
3. Do I need to include auxiliary materials used only in small amounts?
If the auxiliary contributes less than the cut-off threshold (typically 1% per flow or 5% total), it may be excluded. However, if it has high environmental intensity (e.g., chemicals, metals), it’s better to include it even in small quantities. Verifiers expect transparency on these decisions.
4. How should I determine whether packaging materials belong to A1–A3 or A4?
Packaging used during manufacturing or factory handling belongs in A1–A3. Packaging used for transport to the customer belongs in A4. If a material serves both purposes, allocate it based on its primary use or split it proportionally.
5. When should consumables (e.g., lubricants, cleaning agents) be included in A1–A3?
Include consumables when they are required for the normal functioning of the production process and are consumed per unit of product. If they are used very rarely or have negligible contribution, they can be excluded with justification. Always include consumables that significantly affect emissions or resource use.
6. Do temporary materials used during production (e.g., molds, jigs) need to be modeled?
If temporary materials are used repeatedly and their contribution per product is minimal, they may be excluded. If they are used up or replaced frequently, allocate their impacts based on their consumption rate. Document any assumptions for verification.
7. When is it acceptable to exclude a material because its contribution is below the cut-off threshold?
When the material is demonstrably less than 1% of the product mass and less than 5% of total environmental impact. The cut-off rule must never be used to omit environmentally intensive materials (e.g., adhesives, coatings) even in small amounts. Verifiers may challenge exclusions that appear unjustified.
8. How should I model materials that have multiple suppliers with different datasets?
You can average suppliers by mass, volume, or market share, depending on what best represents your product. If one supplier dominates, model that supplier’s data. When uncertainty is high, averaging provides a balanced approach.
9. If a material contains recycled content, how is that represented in A1–A3?
Recycled content reduces the upstream burdens in A1 because part of the material’s life has already been accounted for elsewhere. The dataset should reflect the correct recycled content percentage. Materials with high recycled content often have lower A1–A3 impacts but more complex Module D behavior.
10. How should I treat co-products arising from the manufacturing process?
Co-products should be allocated based on mass, economic value, or other rules defined in the relevant PCR. Mass allocation is common when products are similar in nature, while economic allocation is used when co-products differ significantly. Always apply the allocation rule consistently.
11. What if a material has no available dataset — can I substitute a similar material?
Yes, but the substitute should be as close as possible in composition, production process, and performance. Document your reasoning clearly for the verifier. If no suitable dataset exists, consider using a generic EPD proxy for the material category.
12. How do I model coatings, adhesives, and other finishing materials accurately?
Model these using their mass per product and select datasets that reflect their chemistry (e.g., epoxy, acrylic, polyurethane). These materials often have high impacts per kilogram, so accuracy matters. Include both the material and any required curing or drying energy if relevant.
13. Should energy consumption be allocated across multiple product variants or modeled individually?
If variants share the same production line and similar processes, allocate energy proportionally by production volume or mass. If variants have significantly different manufacturing requirements, model energy separately. Transparency in allocation helps avoid verification issues.
14. How do I report production waste in A1–A3?
Report the waste generated during production using appropriate waste treatment datasets (e.g., recycling, incineration, landfill). The waste must reflect the correct fraction and treatment route. If waste is internally recycled, this should follow the rules for internal scrap loops.
15. If I include recycled materials, do I still need to account for internal scrap loops?
Yes. Internal scrap loops must be considered, especially for metals, and may affect both A1–A3 and Module D. Scrap generated internally generally does not receive Module D benefits, but external scrap does. Follow the A2 amendment rules for recycled content and end-of-life allocation.
16. When is it appropriate to use a generic dataset in A1–A3 vs. requiring primary data?
Use primary data for energy, material inputs, and direct emissions whenever possible. Generic datasets may be used for background processes like raw material production or upstream supply chains. When primary data is unavailable, document your justification clearly.
17. Should water consumption in manufacturing always be included, even if minimal?
Water use should be included when it is part of the manufacturing process, even in small quantities. If the contribution is extremely low, document the reasoning for potential exclusion. Water scarcity impact categories make water data increasingly important.
18. How do I model multi-component products where materials are assembled from different facilities?
Model each facility separately if their processes differ significantly, then allocate based on the share of production. If facilities operate identically, averaged data may be used. Include transport between facilities where relevant.
19. How should I document assumptions when detailed material information is unavailable?
Clearly describe what information was missing, how you estimated or substituted data, and why the chosen approach is reasonable. Verifiers want transparency, not perfection. Good documentation prevents delays and rework later.
2. Energy Use, Electricity Modeling & Renewable Energy
(Questions 20–32)
20. How should electricity consumption be modeled if the factory operates in multiple countries?
Model electricity using each country’s grid mix if production occurs in multiple locations, weighted according to the share of production from each site. If a single product batch can come from multiple factories, use a weighted average. Keep documentation clear about which facilities contribute data.
21. Should I use national grid mixes or supplier-specific electricity data for manufacturing?
Use supplier-specific electricity data when it is well-documented, credible, and verifiable. If this is not available, the national or regional grid mix is the default choice. Always be consistent and report which approach you used.
22. Are renewable electricity certificates (RECs) accepted for modeling renewable electricity?
Yes, but only if the PCR or Program Operator allows market-based electricity modeling. You must have evidence that RECs were purchased and retired for the reporting period. If this cannot be verified, use the location-based grid mix instead.
23. What is the difference between residual mix and grid mix for electricity modeling?
The grid mix reflects the overall energy production composition in a region, while the residual mix represents what remains after deducting renewable energy claims sold through certificates. Residual mix is used in market-based accounting, while grid mix is used for location-based modeling. Use whichever method aligns with the PCR requirements.
24. How do I model self-generated renewable energy (solar, wind) used onsite?
Model onsite renewable energy using a dataset that reflects the specific technology, such as rooftop solar PV. Include all upstream impacts of producing the renewable equipment. If excess energy is exported, follow the PCR’s rules for credits or avoid double counting.
25. Can I model 100% renewable electricity if the company purchases green electricity contracts?
Yes, provided you have evidence that the contract covers the specific plant and production period, and that the Program Operator accepts market-based electricity. Without documentation, the baseline grid mix must be used. Verification requires clarity about the renewable electricity source.
26. How should I model electricity consumption that varies seasonally?
Use annual averages if seasonal variation is minor. If seasonal differences are large and materially affect emissions, consider creating a weighted average based on production volume and electricity use across seasons. Clear justification is key for verification.
27. What dataset should I use if no market-based renewable electricity dataset exists for the region?
Use the location-based grid mix and document the absence of a market-based dataset. If the supplier provides certified renewable electricity, note it in supporting documentation even if you cannot model it directly. Verifiers appreciate transparency about limitations.
28. What happens if electricity use is reported per unit of production rather than per year?
You can use per-unit energy consumption directly if totals are not available. Multiply the per-unit energy use by the declared unit to ensure consistency. Check that the data aligns with the reporting period.
29. How do I determine whether to use market-based or location-based electricity modeling?
Follow the PCR or Program Operator rules first. If they allow market-based modeling and you have verifiable documentation for green electricity purchases, you may use it. Otherwise, default to location-based grid mixes.
30. If a supplier claims to use renewable electricity, what documentation is required?
Acceptable documentation includes energy certificates, supplier contracts, or annual sustainability reports showing proof of renewable sourcing. The documentation must match the reporting period and production site. Without evidence, you must use the grid mix.
31. How should backup diesel generators be modeled when used occasionally?
Include backup generator use if it is regular and measurable. If usage is rare, estimate fuel consumption based on operating hours. Always include direct emissions and upstream fuel impacts if modeling is required.
32. Do I need to include upstream impacts of renewable energy technologies?
Yes. Solar panels, wind turbines, or other renewable technologies have manufacturing and end-of-life impacts that must be included. Use appropriate datasets that capture their entire life cycle, not just the electricity they produce.
3. Transport Modeling (A2 & A4)
(Questions 33–41)
33. How do I choose realistic transport distances for raw materials in A2?
Use supplier-specific transport distances whenever possible. If this information isn’t available, use reasonable and transparent assumptions based on regional logistics or typical supply routes. Verifiers mostly look for logic, consistency, and documentation.
34. What transport mode should be used if the supplier doesn’t specify one?
Choose the most likely transport mode based on geography and industry practice—usually truck for short distances, rail for bulk goods, and ship for overseas transport. If multiple modes are plausible, document your rationale. Conservative assumptions help avoid issues later in verification.
35. Can I combine multiple transport modes (e.g., sea + truck) for a single input?
Yes. Many supply chains involve multimodal transport, and modeling them increases accuracy. Simply break the journey into segments and apply the correct mode and distance for each.
36. How should I represent average transport distance when sourcing from multiple suppliers?
Use a weighted average based on the proportion of materials delivered by each supplier. If the exact proportion is unknown, use simple averaging or market share estimates. Make sure your method is consistent across all materials.
37. Is return transport required to be included?
Generally, no. Transport in A2 and A4 covers the delivery of goods to the next life cycle stage, but empty return trips are normally outside the scope unless specified in the PCR. Only include return journeys when they are explicitly required.
38. If transport packaging differs from product packaging, how should each be modeled?
Model production packaging (used inside the factory) in A1–A3 and transport packaging (used for shipping to customers) in A4. The two packaging types often have different masses, materials, and end-of-life routes, so treating them separately is the correct approach.
39. Should I model transport to temporary storage locations?
Only if temporary storage is a normal or necessary part of the supply chain. If material moves from supplier → warehouse → factory, both legs must be modeled. If storage is optional or unrelated to production, you can exclude it with justification.
40. How do I handle very large differences between minimum and maximum transport distances?
Use either a realistic average or apply the distance that represents the majority of supply volume. If in doubt, choose the more conservative estimate. The goal is to avoid underestimating transport impacts.
41. Are fuel emission factors allowed to come from external datasets?
Yes, but the dataset must be reputable and ideally aligned with EN 15804 or the relevant PCR. Most users rely on built-in fuel datasets from One Click LCA, ecoinvent, or other LCA databases. Always cite the source of external factors in your documentation.
4. End-of-Life (Module C) & Module D
(Questions 42–57)
42. Why do some materials “leave” the system in Module D instead of Module C?
Materials appear in Module D because Module D represents benefits and burdens beyond the system boundary, such as recycling or energy recovery. Module C stops at the end-of-life processing itself (demolition, transport, sorting, incineration). Module D shows the future benefit provided when the material replaces virgin production or fossil energy. So materials “leave” in D when they have a useful second life outside the product system.
43. How is the end-of-life pathway selected for different types of materials?
Use typical industry practices in the region where the product is used, unless the PCR defines a scenario. Metals usually go to recycling, plastics to incineration or landfill, and wood may be reused, recycled, or combusted depending on local regulations. The key is choosing a realistic, documented scenario that reflects expected disposal.
44. What assumptions should be used for demolition energy?
If no project-specific data exists, use typical values for demolition machinery (diesel excavators, cutters) taken from LCA databases or PCR defaults. Demolition energy is usually low compared to A1–A3, so a reasonable estimate is acceptable. Always pair demolition with the correct fuel dataset.
45. How should I model waste transport distances at end-of-life?
Use realistic distances to the nearest waste treatment facilities—landfills, recycling centers, or incinerators. If exact distances are unknown, use national averages or values from waste management databases. Document your assumptions clearly.
46. How do I decide between landfill, incineration, or recycling scenarios?
Choose the scenario that best matches typical practice for your material and region unless the PCR requires a predefined route. Many materials have dominant pathways (e.g., metals → recycling, plastics → incineration or landfill). If multiple routes are reasonable, weight them according to expected proportions.
47. How do I model incineration with energy recovery?
Use the correct incineration dataset that includes both combustion impacts and energy recovery credits. Energy recovery typically provides benefits in Module D because it offsets fossil fuel energy. Ensure the efficiency of the energy recovery process matches the dataset or PCR requirements.
48. Why does the recycling scenario sometimes result in negative emissions in Module D?
Negative emissions occur because Module D includes avoided burdens: the recycled material replaces virgin production, which has higher impacts. For example, recycled steel avoids the production of virgin steel, which is very carbon-intensive. Module D captures this environmental benefit by reporting it as a negative value.
49. Should packaging be given a separate end-of-life scenario from the product?
Yes. Packaging often has different materials and disposal routes than the product itself. In A5 and C modules (construction and end-of-life), packaging usually follows the local waste management rules for household or industrial packaging waste, not product waste.
50. How should hazardous waste be modeled in Module C?
Use specialized hazardous waste treatment datasets that reflect the correct disposal technology (e.g., high-temperature incineration, secure landfill). Hazardous waste cannot be modeled with generic landfill or incineration datasets. Ensure transport to licensed facilities is included.
51. What is the correct approach when the future recycling rate of a material is uncertain?
Use the established recycling rates for that material in the region of use. If no reliable data exists, choose a conservative, documented assumption based on typical recycling performance. Verification depends more on transparency than on perfect accuracy.
52. How do I handle materials with multiple possible end-of-life routes?
Create a mixed scenario by allocating percentages to each route (e.g., 60% recycling, 40% incineration). This is common in plastics and mixed materials. Ensure the weighted scenario reflects actual expected practice.
53. What is the recommended approach for modeling bio-based materials at end-of-life?
Bio-based materials may store or release biogenic carbon as they decay, are combusted, or are landfilled. Use end-of-life datasets that correctly handle biogenic carbon flows according to A2 rules. Document assumptions about degradation or recovery clearly.
54. When should Module D be omitted entirely?
Module D should be omitted when the material has no meaningful potential for reuse, recycling, or energy recovery. This usually applies to inert materials or those that always end up in landfill. PCRs may also explicitly instruct you to omit Module D for certain categories.
55. How should I model steel recycling using the 1:1 substitution approach?
Steel is typically modeled with the closed-loop approximation under EN 15804+A2: recycled scrap replaces an equal amount of virgin production. The producer receives a Module D benefit for the scrap they supply to recycling. Use the correct steel recycling and virgin steel datasets to avoid errors.
56. How should credits from energy recovery be allocated?
Credits are typically applied in Module D because they represent future energy generation beyond the system boundary. The credit should reflect the type and amount of energy produced (electricity, heat) and the fossil fuel it replaces. Ensure that efficiency assumptions match the dataset.
57. Why might Module D impacts differ significantly between datasets?
Module D depends heavily on assumptions about recycling efficiency, substitution ratios, avoided virgin production, and energy mixes. Two datasets for the same material may use different methodological choices, leading to large differences. Always select datasets that reflect the same methodological rules as EN 15804+A2.
5. Allocation, Recycling & Circularity Rules
(Questions 58–70)
58. When is mass allocation appropriate?
Mass allocation is used when co-products have similar physical characteristics or when their economic values fluctuate significantly. Under EN 15804+A2, mass allocation is often preferred because it is stable and transparent. Use it when it represents the real relationship between outputs.
59. When should economic allocation be used instead of mass allocation?
Economic allocation is appropriate when co-products have very different values or when mass allocation would distort the environmental distribution. It reflects the market-driven importance of each output. Always ensure prices represent a stable period and not a short-term spike.
60. How should I handle co-product allocation when prices fluctuate?
Use an average price over a reasonable timeframe (e.g., 3–5 years) to smooth out volatility. Avoid using short-term prices that might misrepresent the long-term economic relationship between co-products. Documentation of pricing sources is important for verification.
61. What allocation rules apply to internal recycling loops?
Internal scrap loops are usually treated under the cut-off approach: material stays within the system and carries no additional burden for being recycled internally. Only external scrap may contribute to Module D. Scrap quality and yield should be documented carefully.
62. How should I allocate impacts for materials produced in multi-output processes?
Use the PCR rules first; if they specify mass, economic, or system expansion, follow them strictly. If no rule is given, choose the method that best represents how burdens are shared. State assumptions clearly for verification.
63. How do I model avoided burdens for recycled materials?
Avoided burdens are calculated by subtracting the impacts of producing virgin materials from the impacts of recycling. This benefit is reported in Module D. Ensure that recycling yields and substitution ratios are accurate and in line with EN 15804+A2.
64. How can I determine recycled content if the manufacturer provides limited information?
Use supplier declarations, product specifications, or industry averages when specific data is missing. When uncertainty is high, choose conservative estimates and document the assumptions. Recycled content must always be reported transparently.
65. How does the cut-off method differ from the 50/50 method and the A2 rules?
The cut-off method assigns no impact to recycled content, while the 50/50 method splits burdens between product generations. EN 15804+A2 uses a closed-loop approximation with detailed Module D handling for recycling. It is more advanced and avoids simplistic assumptions.
66. When should a closed-loop recycling system be modeled?
Closed-loop recycling is used when recycled material replaces the same material without quality loss (e.g., metals). If quality degrades or downcycling occurs, use open-loop recycling. Closed-loop systems typically provide large Module D benefits.
67. How should pre-consumer scrap be handled — allocated or cut off?
Pre-consumer scrap generated within the facility usually carries no upstream burden under cut-off rules. Only the net amount of scrap leaving the system may generate Module D benefits. Document scrap yields to avoid verifier queries.
68. How do I choose between open-loop and closed-loop recycling?
Closed-loop applies when recycled material is used to produce the same material with similar properties. Open-loop applies when recycling produces a lower-grade material or when the material enters a different supply chain. When in doubt, check the PCR or industry conventions.
69. Should material losses during product use be included in allocation or excluded?
Material losses during installation should be included and modeled in A5; losses during use are normally excluded unless specified. They do not change A1–A3 allocation but affect the overall life cycle. For EPDs, focus on production-phase allocation.
70. How do I ensure allocation methods comply with EN 15804+A2?
Always check the PCR first, follow EN 15804+A2’s hierarchy, and avoid arbitrary or inconsistent allocation. Any deviation from the standard must be justified. Verifiers look for methodological consistency above all.
6. Functional Unit, Declared Unit & Product Modeling Structure
(Questions 71–78)
71. How do I choose between a functional unit and a declared unit for a product EPD?
Use a functional unit when the product provides a measurable function over time (e.g., insulation with a defined R-value and service life). Use a declared unit when the product doesn’t have a service-life-based function or the PCR restricts modeling beyond A1–A3. If in doubt, follow the PCR—most construction product EPDs use declared units.
72. What if the product does not have a clearly defined service life?
If the service life cannot be reliably determined or varies depending on application, use a declared unit instead. This avoids making speculative assumptions about performance over time. Only use service life when it is well-established, tested, or specified in the PCR.
73. Should the declared unit always match the sales unit?
Not necessarily. The declared unit must reflect how the product is compared in the market, which may differ from the sales unit. For example, insulation is often sold in m² packs but declared per m² of installed product. Consistency with PCR requirements is more important than matching the sales format.
74. How should I handle products that vary significantly in dimensions or density?
Create a representative product or average if differences are small, or model separate EPDs if the variations significantly affect environmental performance. Some PCRs allow declaring a range. The key is ensuring that the declared unit reflects a product configuration that users can meaningfully compare.
75. How do I determine whether a product’s lifetime needs to be modeled in the EPD?
Only include lifetime modeling if the PCR explicitly requires a functional unit involving service life (e.g., flooring, insulation). A1–A3-only EPDs do not require lifetime assumptions. Use caution—unjustified lifetime values are a common verification issue.
76. What is the correct approach for modular products with many configurations?
Choose either:
-
A representative average product, or
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A modular EPD where parameters can be combined, if the PCR allows it.
If configurations affect impacts significantly, separate EPDs may be needed. Document the modeling logic clearly.
77. Should product variants be included in one model or modeled separately?
If variants differ only slightly (e.g., small dimensional changes or cosmetic differences), they can be included in one model using parameters or averages. If variants have different materials, densities, or production routes, model them separately. Use Sister EPD rules when allowed.
78. How should I model products that require installation materials not included in A1–A3?
Installation materials belong in A5, not A1–A3. Only include installation components in A1–A3 if they are physically part of the product as delivered. Keep the boundaries clear so that manufacturing and installation impacts are not mixed.
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