Modelling as coproducts: from biowaste treatment to nitrogen fertiliser

Question

Hi,

 

I am doing a system expansion of my LCA using the cut off ecoinvent database and one of the products of it is biowaste. I would like to model the following:

biowaste -> compost -> nitrogen fertiliser

I found the following processes in Ecoinvent:

treatment of biowaste, industrial composting | compost

nutrient supply from compost | nitrogen fertiliser, as N 

However I am struggling to connect these processes to obtain my final product "nitrogen fertiliser", as 'treatment of biowaste, industrial composting | compost" is empty in inputs and only has in outputs the flow "compost" (see attached screenshot). So I don't know how much compost is actually produced with the process. Is there a way to find out? Or am I using the wrong database?

 

Many thanks

 

Sophie

Answer 1

Hi Sophie, indeed that is a property of the cut-off model that processes delivering useful "recyclates" (such as compost) are cut from the previous life of these recyclates. So, either model this yourself, or switch to a different system model (APOS) which is maybe better since then your modeling is consistent with the rest of the database.