sorry dont know if it does and if it does, how strong it has to be.

Rhubarb leaves should never be put on the compost heap as they are poisonous. That may be your answer.

although posionous to us there isnt a problem with composting them actually. Too many will affect the pH balance but mixed with other garden waste it doesnt pose a problem. It was part of a research project I was involved with at Uni 30 yrs ago.
When I cook it the 3-5 leaves that go on quickly rot down too.

they do say they are poisonous to insects, but snails will eat away at them,cant be bad 4 them

They are very good at cleaning burned saucepans though.

thats the oxalic acid for you. Apparently you shouldnt cook rhubarb in aluminium pans as it degrades the aluminium and taints food with aluminium salts. I dont use Al foil cartons for rhubarb either.