ecoinvent Forum Archive

Hello, 

I have a hard time to wrap my head around the "treatment of biowaste for anaerobic digestion"-dataset. I'm looking for some kind of climate impact for the production of biogas from biowaste. Is this possible to find from this dataset? If I look at the dataset (allocation, cut of by classification):

"treatment of biowaste by anaerobic digestion"

Reference product: Biogas

Location: CH

LCIA -> IPCC2013

I don't see any climate impact. Is it possible to find this information from any other dataset?

Best regards, Jacob

Dear Jacob, 

See the description of "Handling of Waste Products" in the description of the Cut-off system model. In particular: "Any non-waste by-products of a waste treatment (i.e. not other waste products) are cut off and do not give a credit to the producing activity. The point of cut-off is therefore the end of the waste treatment. This also means that the resulting products are available in the database and can be used as burden-free inputs in other activities." This modelling is specific to the Cut-off system model. 

Best regards,

Lucia Valsasina, Junior Project Manager, ecoinvent

Hello, I have a similar question regadring digester sludge. In the cut-off approach digester sludge ist burden free, when it's used as fertiliser and there are also no credits, when it leaves the biogas plant. Now I saw several paper, where they give credtis for digester sludge, because it replaces mineral fertilizer. Is this legit?

Dear SimonRauch,

Of course it can be legit based on the assumptions and methodology a modeller is taking. Our cut-off system model's assumptions are available in the website.

Kind regards,

Avraam Symeonidis,

Data analyst, ecoinvent Association

Hi, I am trying to compare and understand the GWP of the following biomethane heat and natural gas heat processes:

"heat production, biomethane, at boiler condensing modulating <100kW, RoW"

"heat production, natural gas, at boiler condensing modulating <100kW, RoW"

Using ReCiPe Midpoint (H) method, the GWPs of the biomethane heat and natural gas heat are around 0.014 and 0.069 kg CO2-eq, but I am not 100% sure why biomethane heat has lower GWP, as essentially they are all CH4.

According to the cut-off criteria mentioned previously, because biomethane is produced from anerobic digestion of biowaste (manure, sludge), which is considered burden-free. So the GWP of the biomethane heat process only bears the CO2-eq from the biomethane production processes, while the the biomathane combustion is considered CO2-free. That is why biomethane heat has low GWP. Am I right? Thanks   

@yang_qiu: CO2 emission from biomethane are assumed as climate neutral, at least with ReCiPe. Compare these results with ILCD Impact assessment and you yould see a difference. Further more you should consider the allocatiopn factors, since electricity is the more valuable product. You can also find the not-allocated datasets on the ecoinvent webpage.  Dear Avraam Symeonidis,

thank you four your answer. Shouldn't the modeller respect the methodology of the database he uses? If I receive credits for giving away digester sludge, the farmer should "pay" for this, if he uses the digestate to replace fertiliser. Otherwise my results are not consitent.

An other question is about this dataset: "maize silage production, Swiss integrated production, intensive | maize silage, Swiss integrated production | Cutoff, U"

One input is: "solid manure loading and spreading, by hydraulic loader and spreader | solid manure loading and spreading, by hydraulic loader and spreader | Cutoff, U"

But no manure itself is mentioned as input. Are emissions of manure decomposing assessed, since this contais carbon? Could yoo please send a copy of the answer to simon.w.rauch@fau.de

Dear Simon,

Thank you for coming back to us with your question.

Regarding the literature that gives credit to the for digester sludge, consistency with the methodology of the database is always suggested. However, these type of choices are up to the LCA practitioner to be made and many different approaches can be found in literature papers.

In terms of the maize silage production, the dataset does not include an input of manure, only the service of spreading it. Therefore, there are no emissions manure decomposing assessed.

Kind regards,

Nikolia Stoikou, Junior Data Analyst, ecoinvent association