How do I calculate the transportation phase in LCA?

Question

I have a question regarding the kg*km formula for calculating the transportation phase of LCA. I want to calculate the transportation of 15 kg of a product over 20 km distance by a 3.5-7.5 lorry. However, intuitively it seems to me that emissions from a transportation of 15 kg of cargo over 20 km distance (300 kg*km) should be less compare to transportation of 1 kg of cargo over 300 km distance (same 300 kg*km)? Where am I wrong?

Answer 1

Hello Egor,

You should think of the way this measurement is constructed. A truck uses X liters of diesel to drive a km, and it has Y kg of load on it. We divide the impacts from burning the X liters of diesel, onto the Y kg of load in the truck.

When load of our product is lower, the allocation of impacts from the truck is also lower. As well as, when the truck distance is longer, the amount of impacts to divide onto the load is higher.

When the relationship between load and driving distance is similar, the formula prescribes that the impacts allocated to the product is the same.

This is the reason, why an "intuitive" understanding might not hold up.

I hope this helped

Answer 2

Heavier the load/vehicle, more energy is needed to get it moving - therefore more fuel is consumed. So what reductions you may expect from shorter distance are countered by increased weight in the two cases you mention in the question. Hope that helps to think about this intuitively.

I think though looking beyond carbon emissions, this story might get complicated. Heavier vehicles have higher tire & brake wear particulate matter emissions. So I would imagine there both 300 kg*km's may not be same if those relationships between weight and particulate matter formation are non-linear. Just some early thoughts, haven't done the calculations.