Was just reading recently about the fact that there is only one true 100% biodegradable sposie - just subbing til I find it for you.

ETA: Ok found it on femail, they are called Safeties Nature Nappies and they are sold at Macro. Many of the others use organic materials but do not break down 100% like these do.
HtH.
oh wow! you found somewhere that sells these?!! i used them ALL the time with DD1 and they were FANTASTIC! super absorbent and totally eco friendly! (designed in Aus too! ). ok, off to do some searching...