Accounting for Purchased Metal-Containing Waste under GHG Protocol – Scope 3 Category 1

Greenhouse Gas Protocol
1

Hi everyone,

I’m currently supporting a facility that purchases metal-containing waste for thermal treatment and material recovery, and I’m looking to validate the appropriate GHG accounting approach for this setup under the GHG Protocol Technical Guidance for Calculating Scope 3 Emissions.

Our Situation

  • We purchase metal-containing waste streams from external parties.
  • The waste is treated thermally on-site — pollutants are combusted, and the resulting heat is used directly in our production process (i.e., not for electricity generation).
  • After treatment, metals are recovered and reintroduced into the material cycle.
  • We fall under an EU ETS exemption for the combustion of hazardous waste, with the polluter-pays principle applying to the original generator.

Accounting Interpretation – Category 1

Although the input material is classified as waste, we purchase it and use it as a functional input to our production process. Based on that, we interpret this as falling under:

Scope 3, Category 1: Purchased Goods and Services

According to the GHG Protocol:

“If a company purchases a product or material that contains recycled content, the upstream emissions of the recycling processes are built into the cradle-to-gate emission factor for that product and would, therefore, be reflected in category 1.”

Initially, guidance on Category 5 (Waste Generated in Operations) was considered, due to the nature of the material. However, since the waste is not generated by us but purchased, and used as an input, we now understand that Category 1 is the more appropriate classification.

Questions

  1. Category Confirmation
    Can others confirm that purchased waste used as a raw material input (even if legally classified as “waste”) should be reported under Scope 3, Category 1, and not Category 5?
  2. Emission Factor Challenges
    Emission factors for waste-based inputs are not widely standardized. How have others addressed this?
  • Have you used proxies from recycled materials (e.g. secondary metals)?
  • Which databases (ecoinvent, GaBi, DEFRA, etc.) have you found most suitable for this kind of input?
  1. Scope 1 – Combustion Emissions
    We conduct the combustion on-site and use the resulting heat directly. Our view is that this results in Scope 1 emissions, since:
  • We own and operate the thermal treatment process;
  • The emissions occur within our operational boundaries;
  • And the energy is used internally (not sold).
    Does this interpretation align with others’ understanding of Scope 1 boundaries for self-combusted, purchased waste?
  1. Avoided Emissions from Material Recovery
    After thermal treatment, we recover metals that displace the need for virgin material. According to GHG Protocol, these avoided emissions may be reported separately (e.g., in optional disclosures).
    Has anyone modeled avoided emissions from similar recovery processes, and if so, which approach did you use?
  2. Implementation Experience
    Has anyone gone through GHG accounting for a comparable setup — where waste is purchased as an input, treated thermally, and followed by material recovery?
  • How did you approach the categorization and quantification?
  • Any lessons learned, pitfalls, or data sources you would recommend?

This isn’t a standard case that fits neatly into the typical Scope 3 examples, so I’d really appreciate hearing from others who’ve navigated similar situations.

I hope some of you can share your experiences or interpretations — it would be extremely helpful as we align our approach with GHG Protocol best practices.

Thanks in advance!