Here is an example from today:
I'm using a wood burning stove to heat my house. The same Innovate MTX-L AFR gauge is used both with the stove and with alcohol and gas powered engines.
- The Innovate MTX-L doesn't know it's reading the exhaust gases from burning wood, all it cares about is the contents of the gases in the exhaust. When it measures Lambda=1, all is well, doesn't matter if you are burning wood, ethanol, gas, nitro or whatever.

Why make things complicated with AFR?

I don't need to know the stoichiometric value for burning wood, I don't need to know it for ethanol, I don't need to know it for gas...all I care about is Lambda, and that's what the AFR gauges with oxygen sensors are measuring. If interested, one (or the gauge) can then compute the AFR...