Ecoinvent 3.10 - Municipal incineration - states net energy production incl electricity but not in inputs or outputs

Question

The description for treatment of municipal solid waste, municipal incineration | municipal solid waste | APOS, U in FR( 09ab642c-77db-3f5f-96d1-3b59a2d550a3) says:

Net energy production: 1.39MJ/kg electric energy and 2.85MJ/kg thermal energy.

Can anyone explain why there is no electricity output in the process outputs section? Where we use incineration and it says there is a net electricity output in the description, do we still have to manually do system expansion to reflect the substitution of electricity that would have otherwise taken place? I have looked at lower levels but electricity doesn't appear on the Sankey diagram.

I have checked the Ecoinvent docs and Ecoinvent in OpenLCA seems to have faithfully reproduced it, so that doesn't seem to be the source.

Thanks in advance!

Answer 1

Because it is a multi-output process and the allocation is done according to the APOS system model. You will find the same process delivering "heat, for reuse in municipal waste incineration only" and anther process delivering "electricity, for reuse in municipal waste incineration only".

Comments

Thanks - although how to deploy it is still rather opaque.

If I have some plastic that will be incinerated and will have a useful output of electricity, from your answer I should use the electricity version?

Also - the phrase "for reuse in municipal incineration only" - I speak English as a native tongue but can you clarify what that is supposed to mean? The electricity is to be reused in the incinerator?!!

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Yes, I agree that the system models are not very intuitive and the algorithms behind are not always transparent, since the allocation is not directly visible inside the processes itself. But this would be more a question for ecoinvent, since the openLCA implementation simply follows the exact activities from ecoinvent original data.

As I understand the product flow, the electricity and heat that is produced will be for "reuse in municipal incineration only" so that it is only used internally inside the process (activity). Also in the flow descriptions you will find informations:

"The heat is produced in treatment activities and usually reused in the activity itself. Excess heat is fed in 'market for heat district or industrial, other than natural gas'."

"Electricity that is produced internally in the incineration plant. Excess electricity is fed into 'market for electricity, medium voltage'."

Also be aware that inside this process it is written "Not suitable to represent any single specific waste material, like plastics, paper, cardboard." and you will also find treatment of waste plastics processes in ecoinvent.

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Thank you Conrad - super helpful.

As ISO 14044 preferences substitution, from all of the above, I deduce that I will have to credit the product system with the avoided burdens of generating electricity from the incineration of the plastic. Do you agree? I.e. this is not automatically embedded within the APOS system even though the notes suggest there is a net export?

 (And yes I had noted the process info about not being suitable for a specific waste - I was just using it as an example).