A biodegradable polymer is one that can be broken down by microorganisms (bacteria and fungi) into simple substances such as carbon dioxide and water.Most addition polymers are not biodegradable because their chains contain only strong, non-polar C-C and C-H bonds. Biodegradable polymers instead contain polar bonds in the chain, such as ester links, which can be hydrolysed by water and enzymes.Examples:
• poly(lactic acid), PLA, made from lactic acid obtained from corn starch; used for food packaging, cups and disposable cutlery
• starch-based plastics, used for carrier bags and packing materialsThese are made from renewable plant material rather than crude oil, which helps conserve finite resources. Some polymers are designed to be photodegradable: they contain groups (such as C=O) that absorb ultraviolet light, which breaks the chain, so they break down in sunlight.Advantages: they reduce the build-up of plastic waste in landfill and the environment, they can often be composted, and many are made from renewable resources.Drawbacks:
• they need the right conditions (warmth, moisture, oxygen and microorganisms), usually in industrial composters
• buried in landfill without oxygen they break down slowly and can release methane, a greenhouse gas
• growing the crops uses land, water and fertilisers
• they are more expensive, and they can contaminate conventional plastic recycling if mixed inSo biodegradable polymers are one part of the solution to polymer waste, not a complete replacement.
• poly(lactic acid), PLA, made from lactic acid obtained from corn starch; used for food packaging, cups and disposable cutlery
• starch-based plastics, used for carrier bags and packing materialsThese are made from renewable plant material rather than crude oil, which helps conserve finite resources. Some polymers are designed to be photodegradable: they contain groups (such as C=O) that absorb ultraviolet light, which breaks the chain, so they break down in sunlight.Advantages: they reduce the build-up of plastic waste in landfill and the environment, they can often be composted, and many are made from renewable resources.Drawbacks:
• they need the right conditions (warmth, moisture, oxygen and microorganisms), usually in industrial composters
• buried in landfill without oxygen they break down slowly and can release methane, a greenhouse gas
• growing the crops uses land, water and fertilisers
• they are more expensive, and they can contaminate conventional plastic recycling if mixed inSo biodegradable polymers are one part of the solution to polymer waste, not a complete replacement.