Carbon Capture Modelling

Question

I am trying to model a DAC (carbon capture) unit in open LCA. The output of this process is captured co2. Following this I have another 'refinery' process which uses this captured co2.

I am unable to model this 'captured co2'. If I put co2 emissions to air as an output (with negative values), then I am unable to use this as a provider in the next process. Also if i create a custom flow, then ofcourse openLCA does not realise that I am as a matter of fact, capturing co2.  

Edit: Screenshot attached

Anyone has experience in modelling carbon capture with openLCA ?

Comments

see my answer below?

Answer 1

Good question, there is at present  black & white distinction between elementary flows and product/waste flows. If a flow is an elementary flow, it cannot be used to link processes (as this would contradict ISO). Way out for you: you can model the emitted CO2 as waste, create a new flow for this, and make the capturing process a waste treatment process. I hope this is clear?

Best wishes,

Andeas

Comments

Many thanks for the prompt response. Much appreciated!

However I have a follow up question; since I am capturing this CO2 from the atmosphere, following your method (although it solves one problem) will not give me the 'negative eimssions' that I must expect from the process right ? After all, this capture process is supposed to bring down the emissions of the overall project.

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no, if you model the capture as waste treatment, it will reduce the CO2 emissions and thus I think will work as it should. Maybe try it out (and if you want post the result here?)

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Hello again!

So I tried the following (i am not sure if i understood your advice correctly);
1. created a waste product flow 'captured co2 wtp'
2. created a waste treatment process for carbon capture DAC(waste treatment), with reference flow from (1)
3. created a product flow for co2 as ouput that will be linked to the next process. (If i have waste flow in the output, i cannot link this)

Still I am unable to get overall net negative emissions even if i play with the numbers.
Did I not understand this correct ?
I have attached a screenshot in the original comment.

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what happens with the CO2 that you have now as product on the output side? It is sold? Then this modeling is correct that you have now (screenshot). You have now a process that has two functions, waste treatment and production of CO2, you will need to apply allocation to "get rid of one of the functions" (so to say).

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Thanks for your prompt responses, I really appreciate it!
Co2 is not sold but it is fed into a reactor. For some reason, even if I put an enormous value for 'captured co2 wtp', I still do not get overall net negative co2 eq emissions. Since this 'captured co2 wtp' is a custom created flow, how does the software know that this is actually carbon dioxide ? maybe that is the problem ?

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well maybe then: why do you expect negative CO2 emissions? You catch some of the emissions, so you have less positive emissions, but you do not e.g. take up already emitted CO2 (as a tree would do), so probably the emissions should be just lower? And if the caught CO2 is just stored, I would not have it as output product but make the tank part of this process.

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hmm okay I will add the tank to this process then.

I expect negative co2 emissions because in principle, the DAC unit is actually capturing it from the atmosphere (exactly like a tree would). This is what I need to model.

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ah - so the CO2 is not coming from a technical previous process (such as an incineration etc.)? If it is from the atmosphere, then it is indeed an elementary flow (CO2 in air, resource), and then you can indeed say the output CO2 is the product of this process.

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Yes, it does not come from any previous technical process but directly from the atmosphere.  

Keeping this in mind, do you have an idea of how I can model this atmospheric carbon capture and get negative emissions? I just tried putting an elementary flow with a negative amount but for some reason that does not solve the problem.