Forum for ecoinvent Version 3

Urea production, CO2 uptake

Written on: 10.09.2018#1

Author:
lukasl

Hello,

I would like to ask a detail about the urea production, as N [RER] process in ecoinvent. 

The description claims that CO2-consumption during the production of urea was not included, because it arises as a by-product during the production of ammonia. However, looking at the upstream process of ammonia production hereby the full amount of CO2 is emitted during the ammonia production, not excluding the CO2 which is going to be used for the final urea production (1,46kg CO2/ 1 kg ammonia, liquid).

Does this assumption not lead to an overestimation of the CO2 emissions of urea?

Thank you very much for your consideration.

Best regards,Lukas

Written on: 10.09.2018#2

Hi Lukas,

Thank you for your post. I had a look in the datasets you are mentioning. Based on the documentation, the CO2 input in the urea dataset is not present as it is a by-product of the ammonia production. This specific ammount is not either present in the ammonia dataset you are reffering to and its value is other than 1.46 kg. I am not sure how you calculate that the "full amount of CO2" is 1.46 kg CO2 per kg of NH3 but I hope my answer clarifies your situation. 

Best regards,

Avraam Symeonidis,

Data Analyst, ecoinvent

Written on: 11.09.2018#3

Author:
lukasl

Hi Avraam,

thank you very much for your answer, I appreciate your help very much.

I am wondering why you have a differing value for the carbon dioxide emission in the upstream ammonia production. May I ask how much carbon dioxide is emitted by the ammonia production in your datasets?

In my datasets the process "urea production, an N [RER]" has 1.23 kg of ammonia, liquid on the input side. Following this input to the connected process with the biggest share (ammonia production, steam reforming, liquid [RER]) the output emission of carbon dioxide accounts 1.46 kg per 1 kg ammonia. This represents the original amount of carbon dioxide emitted by the production of ammonia. 

From my perspective this amount of carbon dioxide would have been reduced by the required input of carbon dioxide for urea production.

I understand that it is excluded based on the documentaion, but if you say it is a by-product of ammonia has it not to be subtracted on the output side of ammonia production in the case of a coupled production?

Thank you very much.

Best regards,

Lukas

Written on: 11.09.2018#4

Hi Lukas,

 

First of all, we can clarify a few things as the datasets do not seem to be very intuitive. 1.46 kg of CO2 per kg of ammonia refers to an emission of CO2 (Answer to your question: May I ask how much carbon dioxide is emitted by the ammonia production in your datasets?). This (emission) simply means that during the production of 1 kg of ammonia, 1.46 kg of CO2 escapes the factory boundaries and is emitted to air where ends up in the atmosphere and so on. I hope this is clear enough. Now, during the production of 1 kg of ammonia, there is another amount of CO2 produced that is utilised in the production of urea. This amount of CO2 is not an emission. This amount of CO2 is not present in the urea dataset as input. Same way, it is not present in the ammonia dataset as either output.

I think that your last question is indirectly answered. I hope everything is clear now.

Best regards,

Avraam Symeonidis,

Data Analyst, ecoinvent

Written on: 13.09.2018#5

Author:
lukasl

Dear Avraam,

thank your very much for your answer, I understand the argumentation.

Do you know how much the  another amount accounts and where this CO2 (within the ammonia production) is coming from?

According to the literature used for the datasets (Frischknecht, 1999) only 10% of the CO2 recovered, also stoichiometrically 1,46 kg plus the another amount is not deliverable.

Best regards,Lukas

Written on: 14.09.2018#6

Dear Lukas, 

According to ecoinvent report No 15. (Nemecek T. & Kägi T. (2007) Life Cycle Inventories of Swiss and European Agricultural Production Systems. Final report ecoinvent V2.0 No. 15a. Agroscope Reckenholz-Taenikon Research Station ART, Swiss Centre for Life Cycle Inventories, Zurich and Dübendorf, CH, retrieved from:www.ecoinvent.ch.) in page 84 (or page 89 of the pdf) you can read "CO2 used as input (733 kg CO2/t urea) in urea synthesis arises as a byproduct during the production of ammonia (Althaus et al. 2007) and is therefore omitted." in the box dedicated to the dataset related to urea production.

I think that we have covered the topic. In case you have more questions please make sure you exhaust all the respective documentation and then write to us. 

 

Best regards,

Avraam Symeonidis,

Data Analyst, ecoinvent

Written on: 18.09.2018#7

Author:
lukasl

Dear Avraam,

"I think that we have covered the topic. In case you have more questions please make sure you eshaust all the respective documentation and then write to us"

I don't think the topic is covered, as I was asking about where the output emissions of the ammonia production are coming from which do not refer to the documentation you mentioned. However, I accept your point of view and won't ask here further.

Thanks for your help up to this point.

Best regards

Lukas

Written on: 10.12.2018#8

Author:
mattepey

Dear Avraam,

I would like to ask a detail about the urea production and CO2 release in ecoinvent. 

The description claims that CO2-consumption during the production of urea was not included, because it arises as a by-product during the production of ammonia. So why it is considered the CO2 emitted by hydrolysis of urea during plant cultivation? is not it a double count? 

 

Thank you very much for your help.

Best Regards 

Matteo

Written on: 11.12.2018#9

Dear Matteo, 

Please send me an email at: symeonidis@ecoinvent.org and let me know what plant you are considering, and exactly which urea production dataset you are considering.

Best regards,

Avraam,

Data analyst, ecoinvent

Written on: 11.01.2019#10

Author:
Christoph

Dear Avraam, hello ecoinvent support,I have to revive this discussion because I'm struggling at two points when studying this topic and the process "urea production, as N [RER]" and as well the process "ammonia production, steam reforming, liquid [RER]".I use ecoinvent v3.3.First of all one outcome of the discussion above was that a specific (but unknown) amount of CO2 is assumed to be converted into urea since this is done frequently in real industrial setups. Therefore both processes the ammonia and the urea process disclose the amount of CO2 which is used in the downstream urea production.Here my first question is: If it is assumed that CO2 from ammonia production is used for Urea synthesis, wouldn't it be necessary that the "ammonia" process also considers a specific amount of ammonia which is directly utilized for the urea synthesis? Or is this amount already substracted from the main output of the ammonia synthesis process which is "1 kg ammonia, liquid"? If it this is not considered it would be (from my point of understanding) inconsistent when only bearing for an amount of CO2 which is used but at the same time leave the total amount of ammonia " fully available for the market". Second question arises when studying the related ecoinvent reports which are:- Ammonia: 2007_Althaus_LCI of Chemicals- Urea: 2007_Nemecek_LCI of Agricultural Product SystemsOn PDF-page 183 in Althaus et al. it is stated that "1.23 kg CO2 / kgNH3 are produced in partial oxidation". I assume that it should rather be "1.23 kg CO2 / kgNH3 are produced in steam reforming process" since it is part of the chapter "11.5.1 Ammonia, Steam reforming". Later on p.188 the CO2 production in case of partial oxidation is actually stated with "2.30 kg CO2 / kgNH3 are produced in partial oxidation"If I continue my calculations for the steam reforming process with 1.23 kg CO2 / kgNH3 I end up with my second question to you: In your first post during this topic you mentioned that the Urea (as N) process has no CO2 input since it is assumed that it derives all its CO2 from the Ammonia synthesis. However the Urea process needs 0.733kgCO2 / kgUrea. (Nemecek PDF p.80).Adjusted to the "Urea as N" process this equals 1.59kgCO2 / kgUrea(N) (0.733/46% N-content in Urea).Additionally 1.23kg NH3 are needed for the 1kg Urea(N) production. Based on the values discussed before I calculate a CO2-release for the NH3 production of: 1.23kgNH3 * 1.23kgCO2(emitted)/kgNH3 = 1.51 kg CO2 per needed amount of NH3 for the synthesis of 1 kg of Urea(N).Bottom Line: There is not enough CO2 from NH3 synthesis (based on SMR) for the urea synthesis. Therefore the ecoinvent process dataset "urea production, as N [RER]" should either consider an additional demand of CO2. Or ecoinvent should avoid including the assumption that parts of the CO2 from NH3 synthesis is used for Urea synthesis and leave the decission of CO2 utilization to the user.

Written on: 14.01.2019#11

Dear Christoph,

 

Thank you for reviving this post. Regarding your first question and if I understand it correctly the answer is "no". You can have the ammonia production with some CO2 as emission and some other CO2 as by-product. Then if you use CO2 as by-product in urea you get an induced amount of ammonia production. Instead what is done here is that the CO2 meant as BP from ammonia is not recorded as BP and at the same time for the urea production you do not need ammonia in order to derive CO2 out of it. There is not an inconsistency in the way you define it since you are not burdened from the CO2 from ammonia production. Regarding your second question, unfortunately your calculation is not correct. You do not take into account the market for ammonia but instead you assume that all your ammonia is generated from one type of ammonia production. This is not what is happening in the datasets. At the end, I understand that the way those datasets are modelled might not be crystal clear but you have the possibility to modify them and use them as you are pleased. Besides we are a background database, we are transparent, so we allow users to modify the datasets. You seem to understand the processes, so I encourage you to modify them based on your exact needs. We got additional feedback from users about those datasets and we will consider possible updates or restructuring. I hope I have your understanding, for anything else please text me directly to my email address: symeonidis@ecoinvent.org as long posts do not help the rest of the forum users.

 

Best regards,

Avraam Symeonidis,

Data analyst, ecoinvent