biochar 2030 bounds

[tabeado]

Purpose of this PR

Add an upper bound on biochar for 2030. Assumption is a maximum annual growth rate of 70%.
For reference, the compounded annual growth rate in the 2020s has reached 60% in Europe.

There is no influence on default scenarios. Only relevant to avoid large increases where there are strong mitigation pressure and geologic CO2 storage constraints.

Type of change

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Parts concerned

• ☑️ GAMS Code
• ◻️ R-scripts
• ◻️ Documentation (GAMS incode documentation, comments, tutorials)
• ◻️ Input data / CES parameters
• ◻️ Tests, CI/CD (continuous integration/deployment)
• ◻️ Configuration (switches in main.gms, default.cfg, and scenario_config*.csv files)
• ◻️ Other (please give a description)

Impact

• ◻️ Bug fix
• ◻️ Refactoring
• ◻️ New feature
• ☑️ Change of parameter values or input data (including CES parameters)
• ☑️ Minor change (default scenarios show only small differences)
• ◻️ Fundamental change of results of default scenarios

Checklist

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In the end all checkboxes must be ticked before you can merge.

• I executed the automated model tests (make test) after my final commit and all tests pass (FAIL 0)
• I adjusted the reporting in remind2 if and where it was needed
• I adjusted the madrat packages (mrremind and other packages involved) for input data generation if and where it was needed
• My code follows the coding etiquette
• I explained my changes within the PR, particularly in hard-to-understand areas
• I checked that the in-code documentation is up-to-date
• I adjusted forbiddenColumnNames in readCheckScenarioConfig.R in case the PR leads to deprecated switches
• I updated the CHANGELOG.md correctly (added, changed, fixed, removed, input data/calibration)

Further information (optional)

• Runs with these changes are here:
• Comparison of results (what changes by this PR?):

[Copilot]

Pull request overview

Adds a near-term capacity upper bound for biochar/pyrolysis technologies in 2030 to prevent implausibly large scale-ups under strong mitigation pressure and limited geologic CO₂ storage, assuming a 70% maximum annual growth rate.

Changes:

• Keeps the 2025 upper bound at 70% above the 2025 lower bound derived from 2024 values.
• Introduces a 2030 upper bound by compounding the 2025 upper bound with a 70% annual growth factor over 5 years.

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[LaviniaBaumstark]

should this PR be merged for the next release?

[tabeado]

not 100% necessary, but would be nice. @fschreyer could you have a look? also looping in @amerfort

[amerfort]

Thanks for doing this. I think the upscaling constraint of 70% is useful.
One remark to keep in mind:
What about regions without a 2025 announcement/deployment?
Is it completely implausible that these regions will deploy no biochar in 2030 too? (i.e. REMIND time step is until 2032)
Checking p_boundCapBiochar this is relevant for JPN, REF and MEA. To me this seems ok, as REF and MEA are very unlikely and JPN is such a small region. But biochar deployment is not completely unlikely there I'd say. Maybe good to keep it in mind that we set biochar to zero for 2030 in these regions with this change.

[amerfort]

And maybe for documentation:
In which scenarios did 2030 biochar deployment become unrealistically high? Is this affecting default scenarios?