# Is it possible to create one product system that has multiple target amounts for different unit processes?

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I have a simple example system which includes the following processes:

• Fuel production
• Electricity production
• Lamp production
• Lamp use
• Lamp disposal

I'm trying to simulate what happens when:

• 5 lamps are produced
• 2 years of lamp use
• 1 lamp disposal

I have created a Product System for Lamp disposal which includes all upstream processes, however I can't get more than 1 Reference Flow. Is there a way to select multiple Reference Flows with differing Target Amounts?

in openLCA

by (114k points)
Interesting questions, yes we foresee always one reference flow for a product system, in line with the "functional unit" concept of ISO 14040.

Lamp disposal is of course not really a benefit thus typically also not a functional unit. If you want to address the full life cycle, you could create one process that has as output: 1 life cycle lamp xyz, with inputs from production, use, disposal.

I don't understand though why you are producing 5 lamps but disposing only 1?
by (140 points)
Many thanks for the prompt response.

The original example was used to teach the concept of formulating process matrices (technology, environmental, scaling, production) to solve LCA problems (with Python). The functional unit was very similar to your suggestion, providing light in a house for 2 years. The assumption was made that 1 of the 5 lamps would break and require disposal during the 2-year period.

Within OpenLCA I generated a Product System of the most downstream process, disposal, as a way to capture all upstream processes. It wasn't that disposal was the functional unit, but rather I was trying to ensure all upstream processes were included. Perhaps I should be making use of waste flows.

I appreciate the quick feedback. I'll probably work to use a more realistic example in class.

Thanks!
by (670 points)
As per my understanding, you can do whatever (mathematically) you want in an LCA study with different number of amounts as input (if not as reference flow). The important point is that all interlinks among flows/processes for providing the functional unit must make a logical sense.

In you case, the functional unit could probably be ' providing lighting service in a house for two years' and you can give 5 lamps as input, 2 years of electricity usage, and treatment by disposal for 1 lamp.

I agree with Dr. Andreas Ciroth that the production/disposal quantities of lamps seem un-intuitive, you can still get some results mathematically.