8. The Report also says “Starch-polyester blend bags have a higher global warming potential than conventional polymer bags, due to the increased weight of material in a bag, higher material-production impacts and a higher end-of-life impact in landfill."
9. The Report confirms that biopolymer bags emit methane, which is a greenhouse gas 23 times more powerful than CO2 and that these bags have impacts upon photo-chemical oxidation (smog formation).
10. It has been assumed in the Report that all the agricultural crops used to make the Novamont starch-polyester blend bags are grown in Italy where the film is made, but this needs to be checked, and road and fuel usage factored in from the place where the crops are grown to the polymerisation factory.
11. “The starch-polyester carrier bags weighed almost twice as much as conventional HDPE carrier bags. They had the highest impacts of the lightweight carrier bags in every category apart from abiotic resource depletion. The categories were acidification, eutrophication, human toxicity, fresh water aquatic toxicity, marine aquatic toxicity, terrestrial ecotoxicity, photochemical oxidation, and resource depletion.
12. Abiotic resource depletion is defined as “the depletion of non-living (abiotic) resources such as fossil fuels. In fact starch-polyester bags do have a considerable impact on the depletion of fossil fuels and are therefore not truly renewable, due to the fuel consumed in the agricultural production and transport processes, and in the polymerisation of the material.
13. Bio-based plastics (except for a small proportion made from vegetable wastes) are also in competition with food for the use of scarce land and water resources. The peer-reviewers commented “We think it is difficult to accept the exclusion of the impacts of land-use in a study where also paper, PLA and cotton products are involved, and similarly the impact of water-use is missing.”
14. The oxobio bags should have scored better in the Report even in relation to fossil-fuels. It is true that oxobio bags, in common with all polyethylene and polypropylene bags, are made from oil or natural gas, but this has been extracted in order to make fuels, and plastic is made from an inevitable by product which used to be wasted.
The calorific value of an oxobio bag is the same as the oil or gas from which it was made, and this can be captured in a safe modern incinerator and used to generate heat and/or electricity.
15. Credit for recycling was given to conventional plastic but not to oxobio – on the erroneous basis that oxo-bio bags had a negative impact on the quality of recycling HDPE.
16. Also, oxobio bags are frequently made with a high recycled content.