Engine co2 emissions proof?

[baz-r]

we in the uk can use a diesel for iva exhaust emmisions and can be changed later but sadly it only gets road tax on its engine size but it is a bit cheaper here.

i have always wounderd what would happen if you turned up for an iva running a non petrol/diesel engine like useing svo (neet veg oil) or e85
there is stuff in the manual for gas (cng+lpg),petrol & diesel