I need to assess recycling process of concrete.
But i am confused. I found many processes in the Ecoinvent that i don't know if they represent what i need or not:
1) treatment of waste reinforced concrete, collection for final disposal | waste reinforced concrete | Cutoff, U
2) treatment of waste reinforced concrete, recycling | waste reinforced concrete | Cutoff, U
3)treatment of waste reinforced concrete, sorting plant | waste reinforced concrete | Cutoff, U
(description of processes doesn't have enough information)
I think the problem that i don't understand the idea of negative inputs and outputs. I read some answers about this problem and found that it represents a "mass balance" but i don't understand what is the meaning mass balance.
One of the previous processes has negative output only and the other one has negative input and output. Also, there is another process that has negative input and output but they don't has the same amount (Input= -0.38 kg , Output= -1kg) which is not understandable for me.
I attached the photo below.