Modern miracle? Plastic waste transformed into effective fertilizer

Plastic is one of humanity’s most useful, flexible, and inexpensive inventions. Inexpensive, that is, until you remember the massive environmental and health costs of plastic production and waste.Those costs further incur massive financial costs of fixing (or least reducing) those ecological and medical burdens (transmitted via breathing, eating, and skin-contact), as from Bisphenol A (BPA) and phthalates which can cause heart, kidney, and lung disease, birth defects, and cancer.Approximately 65% of plastic gets used for less than a month, yet will take anywhere from a century to a millennium to biodegrade, while approximately 80% of plastic lies in landfills or open spaces. As much as 10 million tons are polluting the ocean, not only trapping animals like improvised nets but poisoning them and coral in the form of microplastics.So, if someone had a way of turning this global poison into a global ecological and agricultural balm, that’d be good, right? (It’s not a trick question. The answer is yes.)Inspired by Hayao Miyazaki’s 1978 Future Boy Conan anime series which depicted turning plastic into edible bread, Assoc. Prof. Daisuke Aoki at Japan’s Chiba University has done something he calls “very desirable indeed.” In their open-access Scientific Reports paper, Aoki and his co-authors describe a polymer system for transforming waste plastic into “fertilizers that actively benefit ecosystems.”“We are at a critical turning point in the history of plastics,” says Aoki. “While current strategies like reduction and traditional recycling are important, they are inherently ‘passive’ and do not offer active environmental benefits.”Aoki’s previous research already showed how to use aqueous ammonia in a process called ammonolysis (using anhydrous ammonia to depolymerize polyethylene terephthalate into terephthalamide and ethylene glycol) to convert isosorbide-based poly (isosorbide carbonate) or PICs into the glucose-synthesized monomer isosorbide (ISB), urea, and other fertilizing agents.Unfortunately, because PICs were hard and brittle (like other biodegradable plastics), they had limited uses, and their brittleness decreased their use-span, thus increasing waste while prompting even more plastic production for replacement.So, Aoki’s team created an ISB-based plasticizer (a chemical agent that increases flexibility) to make PICs softer and more capable of bending without shattering. It increased elongation at the break point by a factor of more than 10 – from 4.3% to 45.2% – while also ensuring the convertibility of the PIC into fertilizer through ammonolysis. In fact, even the plasticizer itself can be transformed into fertilizer. In experiments, these fertilizers grew Arabidopsis thaliana and komatsuna (a type of Brassica rapa) as effectively as commercially available urea fertilizers did. A poly(isosorbide carbonate) (PIC) plastic made from isosorbide (ISB) units was combined with an ISB-based plasticizer to improve flexibility – ammonia treatment transformed the plastic into fertilizer components that supported plant growthAssociate Professor Daisuke Aoki from Chiba University, Japan “We wanted to move toward an ‘active’ environmental contribution,” says Aoki, “by designing materials that solve the plastic waste problem while simultaneously addressing resource depletion and supporting sustainable agriculture.”If Aoki’s team is successful, plastic could re-enter industrial and consumer life in ways that don’t destroy the global biosphere (not to mention the humans who can’t live without it). Newly designed polymers and plasticizers could help develop more flexible packaging, bags, seedling pots, and agricultural mulch films. Aoki says he anticipates his team’s work could “lead to a fundamental paradigm shift where plastics are no longer viewed as ‘waste’ but as a ‘valuable resource for food production.”Source: Chiba University