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Last edited 10 Jan 2023

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Bio-plastics

1 Introduction
2 Biobased biodegradable materials
3 Compostable vs biodegradable
4 Bioplastic base materials
5 Conclusions
6 Related articles on Designing Buildings

[edit] Introduction

Bio-plastics can made as thermoplastics or thermosets, but as a relatively new field general understanding of their potential is often limited. Bio-plastics are non-recyclable in the sense of the standard processes of recycling plastics, they are however bio-degradable over time might be considered a form of recycling in that they return to their natural state.

[edit] Biobased biodegradable materials

The 2022 paper by Jan-Georg Rosenboom, Robert Langer & Giovanni Traverso 'Bio-plastics for a circular economy" publish in Nature, describes ‘bioplastic’ as a term used increasingly but often misunderstood. 'Bio-plastics are plastics that are either made from renewable resources (‘bio-based’), are biodegradable, are made through biological processes or a combination of these. Some biodegradable but fossil-based plastics are also referred to as bio-plastics, however, the use of this terminology is advised against, as it is misleading' the paper discusses.

'Although most commercial plastics are made from fossil resources, these materials can also be made from renewableresources and are commonly referred to as bio-plastics. In this case, the monomers are extracted or synthesised from biomass compounds (such as sugars in plants) and then polymerised to either make a direct replacement for an existing plastic, such as polyethylene (PE), or novel polymers, such as polyhydroxyalkanoates (PHAs). Biomass extraction can also yield non-synthetic natural polymers, such as starch, natural rubber and proteins.'

[edit] Compostable vs biodegradable

Whilst fossil fuel based plastics are degradable over time through sunlight and weathering, they never fully return to a natural organic state, and thus remain a source of pollution, allowing the leaching of chemicals and micro fragments into the environment. Bio-plastics bio-degrade over time, at varied but faster rates than fossil fuel based plastics leaving behind no toxins or residue. The time that it takes for the plastics to biodegrade relates to them either being defined as compostable ( degrading over a matter of months) or biodegradable (somewhat longer - and by different processes).

Some bio-plastics are compostable in a similar way to organic matter and can be broken down by microorganisms, and will decompose into nutrient-rich biomass in less than 6 months leaving behind no toxins or residue. However most bio-plastics are biodegradable, meaning they can be broken down by microorganisms such as bacteria, fungi and algae into water, carbon dioxide, methane, biomass and inorganic compounds. In many cases bio-plastics that are biodegradable need to be treated in industrial composting plants or treatment centres, however the end result decomposes in the same way as compostable material.

[edit] Bioplastic base materials

There are a great number of bio-based and bioplastic innovations being developed. Below are five examples of common types of base material that are being used to create bio-plastics:

[edit] Starch-based bioplastic

Starch-based bioplastic (often corn starch). Often mixed with biodegradable polyesters to create small hard cases and food packaging.

[edit] Cellulose-based bioplastic

Cellulose-based bioplastic (cellulose esters and cellulose derivatives) can be used for films, moulded frames, and electronic devices

[edit] Protein-based bioplastic

Protein-based bioplastic (wheat gluten, casein and milk) for food packaging and some development of films and coatings.

[edit] Bio-derived polyethylene

Bio-derived polyethylene (fermented raw agricultural materials such as sugarcane and corn) has been used to produce high density polyethylene for crates, trays, bottles and caps, as well industrial containers.

[edit] Aliphatic polyesters

Aliphatic polyesters, are mainly in development phase, sensitive to water, and can be mixed with other compounds. Bio-based polyesters such as polylactic acid (PLA), polyglycolic acid (PGA), poly-ε-caprolactone (PCL), polyhydroxybutyrate (PHB), and poly(3-hydroxy valerate).

[edit] Conclusions

Bioplastics and bio-based polymer materials are still a relatively new field with many innovations developing, some examples are bioplastics created from avacado, banana peel, waste frying oil, rice as well as sugar and CO2. In terms of construction industry the growth of bio-based materials as well as developments in bioplastics are key areas to watch.