Move energy use of carbon-removal to own section

[danielhuppmann]

This PR does the following:

• move the variables for energy use for carbon removal to own section
• switch the ordering of the hierarchy from "fuel - technology" to "technology - fuel" for consistency with other "Final Energy" variables

Open questions: are there other carbon-removal technologies that should be included for reporting of their energy use?

Any comments @IAMconsortium/common-definitions-coordination @gidden?

[gidden]

In the GENIE project explorer, we used "Greenhouse Gas Removal" and included a number of variables (searchable by "Direct Air Capture"): https://data.ece.iiasa.ac.at/genie/#/docs

To be safe, I would include all CDR methods, as most if not all include an energy component to some degree (DACCS, EW, biochar, etc.).

[danielhuppmann]

Thanks @gidden! Not sure how many models have non-CO2 removal technologies at this point explicitly modelled, so I'd prefer to follow the ENGAGE/NAVIGATE template for the time being. We can always add more variables later.

About technologies, GENIE also only reported energy use of Direct Air Capture, so can you suggest a specific list of technologies that should be included?

[strefler]

At least Enhanced Weathering and Ocean Alkalinity Enhancement should be included, but probably also biochar and materials.

[danielhuppmann]

"Ocean Alkalinity Enhancement" added.

About the other options, I'm wondering whether the (additional) energy consumption for carbon removal using materials or biochar can be meaningfully reported? In the sense of a variable Final Energy|Carbon Removal|Materials|Liquids, which should only report the incremental energy consumption for removal, with the main use covered in Final Energy|Industry|Plastics|Liquids (and other industrial sectors)...

[gidden]

Hey @danielhuppmann - here are the list of CDR methods we

DACCU/DACCS Ocean Alkalinization Enhanced Weathering BECCU/BECCS Aforestation/Reforestation Soil Carbon Sequestration Biochar Peatland Restoration Wetland Restoration Agroforestry

In particular, I think DAC, OAE, EW, and Biochar will have nontrivial energy usage. We could also have an "Other" catchall if we want to consider other methods. The additional energy for biochar can definitely be reported, as it requires pyrolysis.

[danielhuppmann]

Thanks @strefler and @gidden!

Anyone willing to approve this PR? Or other items that should be included right away...?

[gidden]

Thanks @danielhuppmann - I think we're almost there. Can you include also Heat as an energy carrier used for CDR? This is relevant to many processes, so I would include for all.

As I write this, I see you have the secondary fuel tag. So actually this is already taken care of, right? If so I am happy to approve.

[danielhuppmann]

Yes, @gidden, the secondary-fuel tag list automatically creates all combinations of the "Final Energy|Carbon Removal|..." variable with the energy carriers listed there (to reduce duplication and mitigate against inconsistent spellings or sub-categorization).

This "auto-complete" is implemented via the nomenclature package, see the user guide.