In the example, the equation is applied to an ‘indirect’ environmental impact. This type of equation can also be applied to situations of ‘direct’ impact (e.g. for allocation of the fuel to one passenger). In most of the situations of ‘direct’ impact, however, the physical relationship is known as well, in which cases the eco-costs might preferably be determined on that direct physical relationship, according to ISO 14041.
Although the authors of the ISO 14041 define economic allocation as a ‘last option’ (to be avoided, if possible) there is no need to avoid economic allocation in cases where the ratio between ‘value’ and ‘kilograms’ is fixed , since the ratio between eco-costs and value, the EVR, is fixed then as well.
So it is a prerequisite for economic allocation that a specific EVR has to be independent of the size (weight, volume, time, etc.) of the functional unit of the element in the LCA. Under this condition, the EVR can be used for direct impacts as well, instead of the eco-costs / weight ratio, which appears extremely practical in many cases.
Note: Since the EVR is a dimensionless number (€/€), price inflation has basically no influence on the calculation, and the EVR is basically the same in each currency (e.g. the British Pound)