Build `.model.transport` on `.model.material` for CircEUlar

[khaeru]

@r-aneeque @macflo8 and I discussed on 2025-02-14.

• For CircEUlar, some scenarios are required for research (exact RQs TBD) focused on the material flows associated with additions to/removals from the stock of (road, passenger) light-duty vehicles.
• There are multiple ways to implement this:
  1. A "soft-link" such as exists between STURM and MESSAGEix-Materials (hereinafter Mix-M). In this, the STURM model is run separately, and some of its outputs are used by code in .model.material to parametrize a representation in Mix-M.
  2. A "hard-link" in which both MESSAGEix-Transport (Mix-T) and Mix-M detail are added to a base scenario.
• We decided that (2) seems a better alternative at the moment. The

In order to implement this, some steps:

1. @khaeru to read and digest the .model.material documentation, with guidance from @macflo8.
2. @khaeru and @r-aneeque to design a method for adapting data received from collaborators at NTNU (LDVs_mat_comp.xlsx, SharePoint/internal) to the structure required for input parameter(s) for .model.material
3. @khaeru to adapt existing code in .model.transport to perform (2), if so configured.
4. @khaeru to construct a workflow that builds Mix-T with these added details/parameter values on top of an existing Mix-M scenario, to be identified by @macflo8.

Work will proceed in 1 or more branches/PRs; this issue is for a central point of reference and to collect information.

[khaeru]

@yiyi1991 FYI we had you in mind when discussing this work. I think the initial version of this will be somewhat simpler than what you need for NGFS:

• For NGFS or a "common BMT workflow", it will be desirable to start from a base model scenario and then layer on buildings, materials, and transport, in whatever order works/makes sense.
• For this, initially, it is sufficient to start from an existing Mix-M scenario. This may change, e.g.:
  • if the CircEUlar RQs require putting different options to the Mix-M build step that align with certain options to the Mix-T build step.
  • if the CircEUlar RQs require using 1 or more of the MESSAGEix-Buildings models alongside Mix-MT.

Eventually the latter may start to converge to the former; we shall see.

[yiyi1991]

Thanks. When you are implementing 2 can you also kindly involve me?

Namely the material intensity that you feed into input_cap_new (and input_cap_ret) for the passenger vehicle technologies, if I understand correctly.