Answer

7. The system we are using is a two step process: initially there is a chemical process where oxygen attacks the carbon chains in the HDPE, turning long chains into smaller and smaller chains which now incorporate oxygen in their chemical make-up. At this point, the plastic has all been turned into organic functional groups (ketones, carboxylic acids, alcohols etc) which attract water. These transformations (smaller chains, and the presence of oxygen and water) create the conditions for a potential second stage: microbial digestion.

If microorganisms are present (as they will be in compost or landfill) then these small fragments will be included in their trophic chain, as food. These fragments therefore decompose further into simple elements: carbon dioxide, water and biomass (biomass is just the organic waste of microbe cells).

This process is similar with the degradation of the lignin in the wood