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Bioplastics explained - what does biobased, biodegradable and compostable mean?

Our phone cases are made of a biobased and compostable bioplastic. But what are bioplastics? Read on, so you know exactly what material your phone case is made of.

The term bioplastic is a bit complicated, as it does not mean one thing and different people use it to describe different things. Bioplastics can have a bio-based content, be biodegradable or biocompatible. Simply put they might be made of plants, are turned to CO2 and water by nature and do not harm you in any way. A bioplastic does not have to be all of the three things combined. This leads to a big family of materials, which all claim the title bioplastic (rightfully), but have quite different characteristics. This might also lead to confusion. Let’s discuss the basics:

 

Plastic explained with a bowl of pasta

Plastic is like a dish of pasta: only the mixture of the right ingredients makes it perfectly tasty

what is plastic?

Plastic is a mixture of different materials that result in a mouldable solid. A plastic is mainly made up of long atomic chains, so called polymers. Polymers are like wet spaghetti and can be deformed during processing. The plasticity of the polymer is also were the name comes from. The polymers are expensive and fragile, so they are always mixed with fillers and additives, such as fibres, mineral powders or organic substances. They are necessary, as they give the final material its properties, such as strength, flexibility, colour, surface texture etc. You can imagine the final product a bit like a bowl of pasta. The long and intermingled spaghetti represent the polymer and the sauce is the fillers and additives.

 

birch-tar biopolymer

Fun fact:

People have been using biopolymers as far back as 200.000 years. Made from birch bark by dry distillation, birch tar was used for example to fix broken pots.

 

Now off to the 3 bios. What does biobased, biodegradable and biocompatible mean?

 

bio-based

A biobased plastic is made from renewable biomass sources such as plants. Examples are starch from corn/rice/potatoes, sugar from sugarcane/sugar beets, cellulose from trees/cotton, vegetable oils from seeds and many more. It can be partly or fully biobased. Maybe you have seen a certificate such as these, some of them even state the biobased content:

 

Certificate Biobased DIN
Certificate Biobased %
Certificate Biobased USDA
Certificate OK-Biobased

How renewable is my plastic? In one certificate you can see “biobased > 85%”, so even a bio-based plastic does not have to be fully made of biomass. The renewable content can be verified by the carbon dating method as carbon from crude oil is a lot older then carbon that comes from renewable sources. The method is also used in archaeology to date the age of fossils and such. Precise science!

 

Determine the biobased content

Biobased content is measurable - with the same method that is used to date fossils!


In the realm of biobased polymers (remember the spaghetti?) quite a variety of different types can be found. First there are the natural polymers. They exist like that in nature. You probably have heard of lignin from trees or chitin from insects and crustaceans. Together with starch, cellulose and proteins they are the most abundant polymers in nature. There are many more to be found in different plants, algae, fungi and bacteria. It truly is a fascinating world.

The natural polymers can also be further processed, this is for example done with cellulose, when it is spun to viscose for those smooth silk-like natural fabrics. Another way to get from natural raw materials like sugar to biopolymers is through fermentation. A well-known example for this is PLA, which is very popular in 3D-Printing as well as packaging. But old school chemical synthesis can be used as well. A special case in this department are so called drop-ins. They are essentially biobased copies of common petrobased plastics. For example the plantbottle from a certain koffein-fizzy drinks company is made from (partly) biobased PET. This means they are chemically exactly the same as their fossil fuel counterparts (and therefore not biodegradable), just made from renewable materials.


Some bioplastics are built from plants that were planted for the sole purpose of bioplastic production – which competes with food production. It is better to use by-products and waste from agriculture like straw or bagasse (sugar cane with extracted sugar) as well as food waste. There are some great ideas and materials, that use all kinds of waste streams, even including sewage sludge. #closetheloop

 

biobased plastics for packaging

Fun fact:

Did you know, that the first modern plastic materials were biobased? Patented in the year 1912, one of the first packaging plastic materials, Cellophane, is still in use today.

 

biodegradable

If degradation happens by biological activity a material might call itself biodegradable. With enough oxygen available for the microbes, fully biodegradable materials leave nothing behind but CO2, water, minerals and biomass. Especially no microplastic particles!

It however does not specify how long this process might take as the duration heavily depends on the conditions. Is it on land or under water? How warm is it? Is there enough moisture? Are the right bacteria around? Your pockets for example do not provide these conditions. That is why your kepu case won't just break down while you use it.

 

biodegradation of bioplastics with the help  of soil microorganism

Biodegradation is only possible because of the help of the microbes and critters living in our soils

 

To solve the timeframe and conditions issue, the term compostable comes into play. This term is exactly defined by normative institutes in Europe and the US. Easiest to define is the “industrial composting”. For a material to pass this test, it needs to lose at least 90% of its weight within 90 days in an industrial composting environment, which is set at about 58°C or 136°F.

“Home compostable” is a bit trickier. The bacteria and other microbes responsible for biodegrading, like it moist and warm. If temperatures drop, they will slow down. You use this tactic everyday with your refrigerator. For a material to pass the “home compostable test”, it therefore has 12 months at ambient temperatures of 20-30°C to lose 90% of its biodegradable weight.

 

compostable plastic

Fun fact:

A compost pile heats itself up because of all the bacteria digesting the biomass. It can reach temperatures up to 60°C or 140°F.

 

But keep in mind that your climate zones and other circumstances will heavily impact the duration if you try it at home. For example, if the ground is frozen during winter, most biological processes are nearly stopped. On the other hand, if you live in a hot humid climate, biodegradation will be faster. Additionally, the thickness and structure of the material also plays a huge role: the thinner the faster. As a rule of thumb, composting biodegradable plastic products is similar to a comparable product made out of wood.

 

To know about the biodegradability of a product or material, look out for these certificates:

 

Certificate biodegradable ok-compost-seedling
certificate biodegradable seedling
certificate biodegradable BPI
certificate biodegradable DIN

 

biocompatible

Biocompatible materials can be used in contact with living beings without it leading to negative impacts. This is very important for materials used in medicine like implants, wound dressings and such. Next to biobased polymers such as PLA biocompatible materials also include petrobased plastics as well as bio-ceramics, medical grade silicons or metal alloys such as titanium.

 

summing up

All this minus the biocompatibility is summed up in this nice little chart, which makes my engineers’ heart very happy:

Bioplastics biobased vs fossilbased and biodegradable explained in one chart

 

There are conventional plastics, that are from fossil resources and not biodegradable. then there are bioplastics, that are made from fossil resources, but are biodegradable. On the other side there are bioplastics, that come from plants but are not biodegradable. And then there are the bioplastics that can do it all: come from renewable sources and go back

 

For every type of plastic there are pros and cons. They all excel in different use cases but that is a topic for another time. We are experts in the field of sustainable materials and always provide the most sustainable material for our products #earthfriendly #biobased #biodegradable #kepu.