The major move in degradable bags has been the inclusion of UV initiated oxidation promoters. Polyethylene naturally UV degrades this happens when the end of a molecule is vibrated off by Uv light it then combines with oxygen to form a peroxy-radical which goes about unzipping polymer chains forming more peroxy-radicals. The plastics industry spends a lot of money on hindered amine stabilizers to stop this happening. The oxidative additive on the other hand promotes this oxidation and even once a bag is denied light ( i.e land fill) the reaction continues once initiated.
The downside is bags with this additive can be mixed in with normal plastic recyclet and destroys the lot, as the chain reaction spreads through the plastic after re-processing
