Does anyone understand what is called semi-continous operation process?

Question

The semi-continuos operation process is an interlinked chain. Examples are

Processes and Material Flow

1. Process 1: Raw Material Preparation

   • Input:
     • Raw material (e.g., eggs or plant biomass): 10 kg.
     • Water: 5 kg.
   • Output:
     • Homogenized slurry: 12 kg.
     • Losses: 3 kg (waste).

   Process 2: Primary Separation

   • Input:
     • Homogenized slurry: 12 kg.
   • Output:
     • Liquid fraction: 10 kg.
     • Solid waste: 2 kg.

   Process 3: Filtration

   • Input:
     • Liquid fraction: 10 kg.
   • Output:
     • Protein-enriched filtrate: 8 kg.
     • Residual impurities: 2 kg.

   Process 4: Precipitation

   • Input:
     • Protein-enriched filtrate: 8 kg.
     • Precipitation agents: 0.5 kg.
   • Output:
     • Protein precipitate: 6.5 kg.
     • Supernatant: 2 kg.

   Process 5: Centrifugation

   • Input:
     • Protein precipitate: 6.5 kg.
     • Supernatant: 2 kg.
   • Output:
     • Concentrated protein: 5 kg.
     • Waste liquid: 3.5 kg.

   Process 6: Washing

   • Input:
     • Concentrated protein: 5 kg.
     • Water: 2 kg.
   • Output:
     • Washed protein: 4.8 kg.
     • Wash water: 2.2 kg (waste).

   Process 7: Dissolution

   • Input:
     • Washed protein: 4.8 kg.
     • Dissolution buffer: 1 kg.
   • Output:
     • Protein solution: 5.5 kg.

   Process 8: Secondary Filtration

   • Input:
     • Protein solution: 5.5 kg.
   • Output:
     • Filtered protein solution: 5 kg.
     • Fine particles: 0.5 kg.

   Process 9: Ultrafiltration

   • Input:
     • Filtered protein solution: 5 kg.
   • Output:
     • Concentrated protein solution: 4 kg.
     • Waste: 1 kg.

   Process 10: Chromatographic Purification

   • Input:
     • Concentrated protein solution: 4 kg.
   • Output:
     • Highly purified protein: 3 kg.(FU)
     • Eluents: 1 kg.

Where the output of the final product is the FU.

But in these processes, it happens when we run the result for answers, the result is usually not consistent in the openlca:  the inputs used is not correllating with the inputs in the result of the ''contributory tree'' in the impact categories.

If there is a method of calculating semi-cpntinous process different from this, kindly advise me.

What could be the problem for this inconsistencies in results and inputs?

Thank you

Popoola

Answer 1

Hi Popoola, first, apologies for a somewhat delayed answer - the contribution tree calculates the entire system as branches, and since often, an LCA system has loops, a process and segments of a supply chain will appear multiple times in different branches. Do not be confused with the results for each of these branches. The overall result is shown in the impact analysis. openLCA will calculate such a system correctly, even though processes are semi-continous. Ideally post a screenshot of the model graph to confirm. Thank you! Andreas