Has anyone calculated the perfect ratios for geode processing?

Here is a couple of production lines for Helmod.

One of them (breaking geodes into dust) isn't perfect, but seem to be close enough.
They are meant for producing pretty large amounts of crystal slurry/crystal catalysts ...

What does does 'Pollution: 80%' in solid fuel description mean?
Does it reduce pollution to 80% when burned? I've tried comparing it to charcoal pellets in a burner and pollution seems to be the same.
Or does reduce it's fuel value by 20% or 80% (to 20MJ or 5MJ respectively)?
Or maybe it doesn't do ...