Compostable Bin Liners

Details

Bin liners certified to IS 17088, the Indian Standard for compostable plastics, with the CPCB certificate number printed on the carton. That number is the only thing separating a genuinely compostable bag from the many bags in this market that print a leaf on ordinary polyethylene. Having said which, the certification means something narrower than the word compostable suggests, and this is the sentence the category exists on. IS 17088 and its international twin ISO 17088 are INDUSTRIAL composting standards. The test runs at 58 C plus or minus 2, which is the temperature of a managed windrow or an in-vessel composter, and the pass mark is 90 percent disintegration within 84 days at that temperature. A home compost pit in an Indian courtyard runs at 25 to 40 C, and at 30 C this bag will take six to twelve months and may still leave visible fragments. The home-composting schemes are different certifications entirely and we hold none of them. So: this makes sense if your wet waste actually reaches a society composter, a municipal wet-waste stream that genuinely composts, or a hot pit you turn. If your wet waste goes into a mixed truck to a landfill, it will not compost meaningfully there, because nothing composts without oxygen, and this bag buys you nothing except a clean conscience. We would rather sell fewer bags than sell that.

• Material named in full, because compostable does not mean made from plants and this is where the marketing goes furthest: PBAT 50 percent, PLA 20 percent, thermoplastic maize starch 28 percent, processing aids 2 percent
• PBAT, polybutylene adipate terephthalate, is a petroleum-derived polymer. It is the largest single component of this bag and of nearly every bag sold as maize-starch based, and a listing that leads with maize starch and never mentions PBAT is telling you the flattering third of the recipe
• No polyethylene and no oxo-degradable additive. Oxo-degradable is ordinary plastic carrying a transition-metal salt that makes it fragment faster into microplastic. It is not composting, it is shredding, it is banned in several countries, and CPCB does not recognise it as compostable
• No printed dye
• 25 micron film, seam sealed. A Medium bag carries 5 kg of wet kitchen waste and holds at the seam, which is where a cheap compostable bag fails
• Disintegration, both figures: 90 percent within 84 days at 58 C to IS 17088, and six to twelve months at a 30 C home pit temperature with fragments possible
• Shelf life 12 months, kept dry and out of sun, because a bag designed to hydrolyse begins doing so the moment it is warm and damp
• Cost per bag is Rs 6.63 for the Small, Rs 8.30 for the Medium and Rs 18.60 for the Large
• Outer carton is kraft paper, not a plastic sleeve