I have been warned by experienced colleagues not to get caught in the life cycle swamp. Still, analyzing well-to-wheel efficiency is very useful in order to understand how different energy sources are used most efficiently.
It works in both directions.
For example: For an energy user it is possible to calculate which energy provider gives the lowest environmental impact.
For an energy provider it is possible to find how the energy is best used.
Most often, it is found in the first round that we all should use hydro power. But the limited availability of the most environmentally friendly energy sources makes the task more complex. This means that we need to find different energy sources for different users.
This is when I mostly get stuck. However, we know that decreasing the energy use should always be right, independently of which energy source we use.
We know that the energy use of an average European city bus is:
Diesel: 5.00 kWh/km
Gas: 6.55 kWh/km
We calculate the electric bus energy use to be: 1.4 kWh/km.
No doubt, it is better to run a bus on sustainable electricity than on diesel or gas. But, this is no surprise.
Now lets turn the question around. If we start from biomass, which route gives the highest efficiency?
Biomass -> Gasification -> Biogas -> Gas Bus
Biomass -> Gasification -> Biogas -> Electricity -> Electric bus
According to my calculations the detour via electricity turns out to be more favorable.
But there are many uncertainties. I would therefore like to challenge anyone reading this blog to provide data or references for the well-to-wheel calculation for gas buses running on biogas from generic biomass, and for the corresponding electric bus running on electricity generated from generic biomass (preferably via gasification).
Well-to-tank efficiency is: 54%
Tank-to-wheel efficiency is: 17%
Well-to-tank efficiency is: 39%
Tank-to-wheel efficiency is: 75%