Innovations in plastics

linear petroplastics economy

99% → resource extraction (petroleum, bio-based) → production → distribution → consumption → waste → 12% incinerated/79% in landfill or the natural environment → 9% recycled

reality

• most chemically recyclable polymers are polyesters: PLA (polylactic acid) and PET

• chemical recycling for PLA and PET involves upcycling by depolymerization

• plastics can only be modernized with new recyclable materials, but these must be industrially and economically feasible

why plastics don’t biodegrade

• petroplastics are not inherently biodegradable by natural enzymes

• many plastics contain additives such as dyes, fillers, flame retardants, plasticizers, and stabilizers which are toxic to organisms preventing biodegredation

3Rs

• need efficient collection

• need efficient sorting

• additives make recycling difficult

• chemical recycling is expensive

circular plastics from petroleum

petroleum → design → production, remanufacturing → distribution → consumption, use, reuse, repair → collection → recycling → environmentally safe waste

Recyclable petroplastics: general scheme

polymerization/depolymerization cycle: monomers → polymers → products → repurposing process: building blocks for new materials

recyclable petroplastics: challenge of additives

toxic stabilizers, plasticizers, or heavy metals could impact health or the environment

Bioplastics from starch: fermentation to polylactic acid

carbohydrate source: starch from grains & food waste → fermentation → lactic acid → polylactic acid (PLA)

Biodegradable bioplastics from wood lignin

• most abundant aromatic biopolymer on earth; interacts strongly with other cell wall polymers

• useful feedstock for plastics, carbon fibers, fuels

biodegradable bioplastics from coconut coir

shell/skin/copra/husk (has lignin, cellulose, and hemicellulose) → sodium hydroxide + sodium sulfite (removal of lignin and hemicellulose, exposure of -OH surface groups) → CH-Raw/B/Bleach → hydrogen bonding among neighboring cellulose molecular chains

biodegradable bioplastics from seaweeds

seaweed → polysaccharides from seaweed → bioplastic pellets → processed to products

biodegradable bioplastics from chitosan (shrimp waste)

crustaceans (shrimp, crabs, lobsters) → chitin powder → chitin hydrogel → hot-pressing → chitosan bioplastic

niche products

cassava bag, cassava garbage bag, sugarcane food box, bamboo cutlery, wooden cutlery, rice straw

Circular Petroplastics and Bioplastics

agroforestry → agro-based feedstocks/lignocellulosic feedstocks/organic waste feedstocks → single-use plastics → biowaste stream (organic waste feedstock, fermentation, other uses)