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0015. Brightway as an optional LCA backend; licensed third-party data is linked or fetched, never shipped

  • Status: Accepted
  • Date: 2026-10-22 (Brightway backend); ChemSep data unshipped on 2026-10-23

Context

LCA backgrounds (ecoinvent and similar) and some thermodynamic parameter sets carry licences that forbid or do not clearly allow redistribution. cheme-as-code is AGPL-3.0-or-later licensed and meant to become public; a plant study must be usable and publishable without a licensed database.

Decision

  • LCA has two backends: factors (the project's own characterised factors in lca/factors.yaml, plus packaged open profiles with recorded licences) and brightway (extra lca, adapter integrations/brightway.py). The Brightway project is the user's own and is only read; background activities are referenced by database, name, reference product and location; cheme writes no foreground database into it. Foreground, background links and results stay separate layers, and a source registry records each source's terms and publication policy.
  • Data whose licence does not clearly allow redistribution is not shipped. The ChemSep SRK interaction parameters were removed from the package; cheme data fetch chemsep-srk downloads them per user into the user data directory (foundation/userdata.py), with a recorded checksum.

Consequences

  • Positive: the package and the example plants stay redistributable; results record which licensed sources they used.
  • Negative: users must obtain licensed databases themselves; results with a licensed background cannot be reproduced by someone without the licence.
  • Negative: features relying on fetched data need an explicit setup step; the code names the fetch command (FETCH_COMMAND in thermodynamics/chemsep_srk.py) when the data is absent.
  • Open: the ChemSep IPD licence is still unconfirmed.

Evidence

  • Brightway backend: pyproject.toml extra lca.
  • ChemSep: CHANGELOG "ChemSep SRK data no longer shipped", src/chemeascode/domains/process/thermodynamics/data/chemsep/SOURCE.md.
  • lca.md ("Open data, sources and coverage").