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This is specifically a biodegradable polyurethane. It's just one kind of plastic and not suitable for everything. We have others including old stuff like cello

This is specifically a biodegradable polyurethane. It's just one kind of plastic and not suitable for everything. We have others including old stuff like cellophane, pPLA, PGA, PGL, PHB even biodegradable polyesters... They're cheap. They can be fiber reinforced as needed. However... The tricky bit is that almost always they need to be properly composted to decompose. This is called procedure 7 and cannot be usually applied to plastics that have a pigment added or are painted - the additives would poison the compost heap or leech. You need to be particularly choosy about paints and plasticizers if you want it to decompose safely.

contingencies 2y ago
Another problem is the cost. Mostly in energy. We have had these sugar cane or corn starch based biopolymers for years that nominally degrade to nothing, the reason nobody uses them (except facts-not-required corporate greenwashing purposes) is that the amount of energy you have to spend to get the input processed to the required state lies very much within the "totally ridiculous are you kidding" range. Also, it turns out if you can't leave your packaging on the shelf for awhile and have it maintain a known state, it's less useful than the other stuff. Especially in developing countries with limited infrastructure (which is where the volume is) and where supply chains are likely to be exposed to high temperature and humidity which is exactly the environment required for accelerating breakdown...
- sourdoughness 2y ago
  This is the question I come back to: a crucial advantage of plastic is that nothing eats it. What’s the missing step that allows things to eat it, but only when we’re ready for them to?
  - contingencies 2y ago
    Perhaps long term exposure to the fungisphere? Perhaps the breakdown should be by fungal digestion to inert bio-molecules not physical abrasion to forever-threatening microplastics. But I'm neither a chemist nor a microbiologist, just an amateur dilettante retro-industrialist roboticist. People say "hey it should degrade" but the problem is degrading generally means worse properties. If you think about the qualities of polymers in actual use... at least in the food chain ... a thin layer allows water tightness, resistance to high temperatures (>100°C), thin deposition so materially efficient. This is hard to match with a "discard in to nature without fear" material. The best match is actually .. palm leaves, which - surprise, surprise - are a recognised packaging and water-proofing material in a large number of premodern cultures. The fallback option in evidence with such cultures (still in India) is low-grade pottery, which result by physical abrasion in dirt. Perhaps we should just train a plant to grow watertight, microwave safe noodle bowls and be done with it.
electricships 2y ago
We have plans for (millions) of HPDE sea floaters which should last for 10-20 years (structural strength is not a major issue iirc) Is there a pathway to replace these with recycled plastic something? would love for this to come fr9m OceanCleanup plastics somehow
westurner 2y ago
Any thoughts on CO2 + Lignin for the same applications? "CO2 and Lignin-Based Sustainable Polymers with Closed-Loop Chemical Recycling" (2024) https://onlinelibrary.wiley.com/doi/10.1002/adfm.202403035 https://onlinelibrary.wiley.com/doi/10.1002/adfm.202403035 - https://news.ycombinator.com/item?id=40079540 https://news.ycombinator.com/item?id=40079540 (Edit) "Making hydrogen from waste plastic could pay for itself" (2024) https://news.ycombinator.com/item?id=37886955 https://news.ycombinator.com/item?id=37886955 ; flash heating plastic yields Graphene and Hydrogen "Synthesis of Clean Hydrogen Gas from Waste Plastic at Zero Net Cost" (2023) https://onlinelibrary.wiley.com/doi/10.1002/adma.202306763 https://onlinelibrary.wiley.com/doi/10.1002/adma.202306763

contingencies 2y ago

Another problem is the cost. Mostly in energy. We have had these sugar cane or corn starch based biopolymers for years that nominally degrade to nothing, the reason nobody uses them (except facts-not-required corporate greenwashing purposes) is that the amount of energy you have to spend to get the input processed to the required state lies very much within the "totally ridiculous are you kidding" range. Also, it turns out if you can't leave your packaging on the shelf for awhile and have it maintain a known state, it's less useful than the other stuff. Especially in developing countries with limited infrastructure (which is where the volume is) and where supply chains are likely to be exposed to high temperature and humidity which is exactly the environment required for accelerating breakdown...

sourdoughness 2y ago
This is the question I come back to: a crucial advantage of plastic is that nothing eats it. What’s the missing step that allows things to eat it, but only when we’re ready for them to?
- contingencies 2y ago
  Perhaps long term exposure to the fungisphere? Perhaps the breakdown should be by fungal digestion to inert bio-molecules not physical abrasion to forever-threatening microplastics. But I'm neither a chemist nor a microbiologist, just an amateur dilettante retro-industrialist roboticist. People say "hey it should degrade" but the problem is degrading generally means worse properties. If you think about the qualities of polymers in actual use... at least in the food chain ... a thin layer allows water tightness, resistance to high temperatures (>100°C), thin deposition so materially efficient. This is hard to match with a "discard in to nature without fear" material. The best match is actually .. palm leaves, which - surprise, surprise - are a recognised packaging and water-proofing material in a large number of premodern cultures. The fallback option in evidence with such cultures (still in India) is low-grade pottery, which result by physical abrasion in dirt. Perhaps we should just train a plant to grow watertight, microwave safe noodle bowls and be done with it.

electricships 2y ago

We have plans for (millions) of HPDE sea floaters which should last for 10-20 years (structural strength is not a major issue iirc) Is there a pathway to replace these with recycled plastic something? would love for this to come fr9m OceanCleanup plastics somehow

westurner 2y ago

Any thoughts on CO2 + Lignin for the same applications? "CO2 and Lignin-Based Sustainable Polymers with Closed-Loop Chemical Recycling" (2024) https://onlinelibrary.wiley.com/doi/10.1002/adfm.202403035 https://onlinelibrary.wiley.com/doi/10.1002/adfm.202403035 - https://news.ycombinator.com/item?id=40079540 https://news.ycombinator.com/item?id=40079540 (Edit) "Making hydrogen from waste plastic could pay for itself" (2024) https://news.ycombinator.com/item?id=37886955 https://news.ycombinator.com/item?id=37886955 ; flash heating plastic yields Graphene and Hydrogen "Synthesis of Clean Hydrogen Gas from Waste Plastic at Zero Net Cost" (2023) https://onlinelibrary.wiley.com/doi/10.1002/adma.202306763 https://onlinelibrary.wiley.com/doi/10.1002/adma.202306763