I believe you have understood how it works, but there are some other details that perhaps you should know. Examples: If an activity produces electricity from burning coal, the determining flow is the product output flow ‘electricity’. If an activity produces simultaneously electricity AND heat from coal, then either electricity OR heat will be the determining flow. Waste example: You described an activity that converts waste into something else. For example this could be incinerating municipal solid waste to generate electricity. In this case the ‘treatment of municipal solid waste’ is the determining product output flow of the ‘waste incineration’ activity that has also another product output flow of ‘electricity’. Electricity is not the determining flow here because as you rightly concluded we burn  waste because we want to get rid of it (or in other words: we don’t produce more waste just because we want more electricity...).

Summing up:

- the determining flow is always a product output flow

- activities can have multiple product output flows, but

- there is only one determining flow per each activity

- ‘product’ is a generic term that includes both ‘goods’ (e.g. coal) and ‘services’ (e.g. treatment of waste)

Now the confusing thing here is that ‘waste treatment’ is a product flow (a service in fact) but *sounds* like an activity. Same with ‘transport’. So the next question for the LCA people in this thread is: how are we going to represent waste flows in the schema? My only reference for names is ecoinvent but I don’t think that is really super understandable (my students generally have a hard time understanding them, for example)

Massimo

What is the utility and the actual definition of a "reference flow"?

The more semantically precise term is actually "determining flow".

The definition is: "Flow of an activity for which a change will affect

the production volume of the activity"

The utility is to be able to distinguish the flow that drives (causes)

the activity from flows that are caused by the activity.

Now I see,
so, as you suggested earlier, a waste can be the determining flow as input of a waste disposal activity that produces something else, because we need to dispose of this waste.

Is this correct?


Thanks a lot for the clarification.

Matteo




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Matteo Lissandrini

Department of Computer Science
Aalborg University

http://people.cs.aau.dk/~matteo