Truck size and frequency of waste collection on openLCA model

Question

I have a question about LCA transportation model.

I need to put the per tonne.km value for the truck model in the ecoinvent truck process. 

The waste is beting collected and trasported between point A to B. The functional unit is 1 tonne.

I have two trucks which carrying the waste between A and B. One truck is smaller which collects waste every week and the other bigger one collects the waste every other week because it has higher capacity. 

My question is when putting the km tranport in the truck process, should I put double the distance for the smaller truck or the same for both trucks?

I believe I need to use similar distances in both truck models in LCA model in ecoinvent since the smaller truck model already has about 30% higher fuel consumption per ton.km transport of goods. So it seems that it has already been considered in the ecoinvent truck model.

My truck models:

transport, freight, lorry, 16-32 metric ton, EURO6

transport, freight, lorry, 7.5-16 metric ton, EURO6

Your answer would be quite helpful for me.

Answer 1

Nice question - the answer I think depends on the functional unit of your system; e.g., it could be "provide waste management for a certain area for a certain daily amount of waste (and so on) for 4 weeks", so for a certain time, then you would need to model the number of trips for the trucks with the transported waste amount during this time. So:

2km distance:

Small truck, 4 trips, 3 t -> 2*4*3 tkm; large truck: 2 trips, 6t -> 2*2*6 tkm

Hope this helps!