How can I compare the price of (bio)CNG and (bio)LNG with the price of diesel if one is priced per kilogram and the other per liter?

To fairly compare the price of (bio)CNG and (bio)LNG with diesel, it is important to look beyond the price at the pump and focus on the energy content of each fuel. Although diesel is sold per liter while (bio)CNG and (bio)LNG are priced per kilogram, these fuels ultimately power a vehicle based on the amount of energy they contain. Converting prices to a common energy basis, such as cost per unit of energy, allows for a like for like comparison.

In simple words: if you spend the same amount, on diesel or on (bio)CNG, you may find that even if the (bio)CNG price per unit appears higher at the pump, its higher energy content often allows you to drive further on (bio)CNG.