Attribute waste emissions to energy-related emissions of sectors based on historical shares and remove waste emissions variables from energy-related emissions taxonomy

[fschreyer]

The change addresses this issue by attributing the newly introduced waste emissions in REMIND to sectors via a post-processing in the reportEmi() function. Waste emissions are thereby removed from taxonomy of energy emissions (variables with +), such that e.g. Emi|CO2|Energy|+|Waste (Mt CO2/yr) becomes Emi|CO2|Energy|Waste (Mt CO2/yr).

The attribution to sectors happens in the following way:

• Emi|CO2|Energy|Waste|Plastics Incineration is distributed across Supply|Electricity, Supply|Heat, Demand|Industry and Demand|Buildings based on 2019 historical shares of waste energy use of the sectors from IEA data (derived by this function from @fbenke-pik ).

• Emi|CO2|Energy|Waste|Feedstocks unknown fate (Mt CO2/yr) is attributed to industry in line with the accounting we had before the explicit feedstocks implementation. It refers to emissions from non-plastic materials. Note that accounting of these emissions is currently switched off in REMIND by default (cm_feedstockEmiUnknownFate is off) such that this only applies if chosen intentionally. In case of industry, waste emissions were attributed to subsectors (steel, cement etc.) by the FE solids share of a subsector in total industry solids.

These are the reported waste emissions variables with this change:

> grep("Emi\\|CO2\\|.*Waste", getNames(testReport, dim=3), value=T)
 [1] "Emi|CO2|pre-CCS|Energy|Demand|Industry|Other Industry|Solids|Waste (Mt CO2/yr)"
 [2] "Emi|CO2|Energy|Waste|Plastics Incineration (Mt CO2/yr)"                        
 [3] "Emi|CO2|Energy|Waste|Feedstocks unknown fate (Mt CO2/yr)"                      
 [4] "Emi|CO2|Energy|Waste (Mt CO2/yr)"                                              
 [5] "Emi|CO2|Energy|Supply|Waste (Mt CO2/yr)"                                       
 [6] "Emi|CO2|Energy|Demand|Waste (Mt CO2/yr)"                                       
 [7] "Emi|CO2|Energy|Supply|Electricity|Waste (Mt CO2/yr)"                           
 [8] "Emi|CO2|Energy|Supply|Heat|Waste (Mt CO2/yr)"                                  
 [9] "Emi|CO2|Energy|Demand|Industry|Waste (Mt CO2/yr)"                              
[10] "Emi|CO2|Energy|Demand|Buildings|Waste (Mt CO2/yr)"                             
[11] "Emi|CO2|Energy|Demand|Industry|Solids|+|Waste (Mt CO2/yr)"                     
[12] "Emi|CO2|Energy|Demand|Industry|Other Industry|Solids|+|Waste (Mt CO2/yr)"      
[13] "Emi|CO2|Cumulated|Energy|Waste (Mt CO2)" 

It was checked that all variable summations affected by this change are fulfilled. Moreover, waste emissions were added to the cs2 plots.

See example scenario plots: /p/projects/ariadne/remind/compScen-Check_WasteEmi_Reporting-2024-08-12_13.56.28-H12.pdf.

Tagging @robinhasse and @orichters fyi.

[orichters]

A challenge that I see is that the fix for NAVIGATE and similar for AR6 will then yield the wrong result. But I would also prefer not to take it out because ideally piamInterfaces yields correct results also with older mif files.

The a bit ugly solution I see is subtracting Emi|CO2|Energy|Waste|Feedstocks unknown fate and Emi|CO2|Energy|Waste|Plastics Incineration again from the variables, neutralizing the fix for people that have the new reporting.

Then, after the next release is out, of course, kick these fixes all out.
Best,
Oliver

[0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q]

Waste emissions are thereby removed from taxonomy of energy emissions (variables with +), such that e.g. Emi|CO2|Energy|+|Waste (Mt CO2/yr) becomes Emi|CO2|Energy|Waste (Mt CO2/yr).

I would challenge this statement. They are removed from the automated summation checks, but the plus-notation does not constitute a taxonomy. Not in my view, and I expect not in the view of people only "consuming" REMIND output, which usually never see any variables with the plus-notation.

Is my understanding correct that the Emi|CO2|Energy|Waste equals the sum of Emi|CO2|Energy|Supply|Waste and Emi|CO2|Energy|Demand|Waste? The IEA has "MEMO" categories for that, maybe we should do that too.

[orichters]

I agree with Michaja on this one. Emi|CO2|Energy Supply and Demand|Waste? That would be very transparent and also avoid the piamInterfaces mess.

We have such variables sometimes, such Emi|CO|Energy Supply and Demand.

Which leads me to the question why it is Emi|CO|Energy Demand|Buildings but Emi|CO2|Energy|Demand|Buildings, notice the difference between using " " or "|" between Energy and Demand. So maybe rather use Emi|CO2|Energy|Supply and Demand|Waste and adapt that for the rest as well?

[fschreyer]

Is my understanding correct that the Emi|CO2|Energy|Waste equals the sum of Emi|CO2|Energy|Supply|Waste and Emi|CO2|Energy|Demand|Waste?

Yes.

The IEA has "MEMO" categories for that, maybe we should do that too.

Sounds like a larger project.

I agree with Michaja on this one. Emi|CO2|Energy Supply and Demand|Waste? That would be very transparent and also avoid the piamInterfaces mess.

Not sure I understand this right. So, you would like to rename Emi|CO2|Energy|Waste to Emi|CO2|Energy Supply and Demand|Waste because people would then understand more easily that Emi|CO2|Energy|Waste is contained in Emi|CO2|Energy|Waste|Supply and Emi|CO2|Energy|Waste|Demand and not a separate item. Well, then we would also need to come up with something for Emi|CO2|Energy|Supply|Electricity+Heat... to make clear that Supply|Waste is included there. That does not seem practical. I guess we'd rather need Memo items as Michaja suggested.

Generally, people "consuming" REMIND mif-files without pluses (or without knowing what they mean) can, in theory, anyways only guess taxonomies. Like from the naming structure they would not know that they should not add up Energy|Demand|Solids and Energy|Demand|Industry. I am unsure of whether our naming decision here can be of any help to their hard lifes. I think staying close to the IAMC naming standard (Energy|Waste, Energy|Demand|Waste ...) is the most useful as this is what people in our group are used to.

Which leads me to the question why it is Emi|CO|Energy Demand|Buildings but Emi|CO2|Energy|Demand|Buildings, notice the difference between using " " or "|" between Energy and Demand.

The power of choosing variable names when there is no standard.

[0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q]

For checking the sectoral contributions, sectoral waste emissions variables were added. In case of industry, waste plastic emissions were accounted to the "Other Industry" sector. This is a simplification but given the small contributions of waste emissions overall, a further subdivision of waste emission into industry sectors does not appear to be necessary.

I think this is severely skewing the emissions and emission intensities of the industry subsectors, especially early on, where people in e.g. the ARIADNE project will look closest.

EU27_NZ_CCS100Mt 2025	DEU (Mt)	DEU (%)	World (Mt)	World (%)
Cement	12.0	9.5 %	821	9.8 %
Chemicals	32.5	26 %	1634	19 %
Steel	30.5	24 %	2201	26 %
Other Industry	32.8	26 %	2965	35 %
Waste	18.7	15 %	795	9.4 %
Other Industry + Waste	51.5	41 %	3760	45 %

All waste is deemed to be solids (OK), but Other Industry is the subsector with the second lowest share of solids use. The most likely candidate would be Cement in my view, which is known to gobble up everything that is cheap and burns. Even steel throws some old tyres into blast furnaces. So this is something that might come back to bite us.

What is troublesome analytically is that there is no energy flow associated with Emi|CO2|Energy|Demand|Industry|Other Industry|Solids|+|Waste. I know it is beyond the scope of this fix, but this is skewing the carbon intensity of the Other Industry sector, which will require extra work to sort out if somebody is looking at that.

[orichters]

Sounds plausible. So we have to live with mapping fixes for a while, but we will survive that.

[fschreyer]

Attribution of waste emissions to industry subsectors is now based on sectoral solids share in total industry solids to minimize the issues raised above.