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Sophie Benson
Biomaterials and bioplastics are grouped together as they’re both thought to be derived from natural resources. Biomaterials are, by definition, sourced from nature; wood pulp, plant cellulose, food waste, grass, algae, and mushrooms are all used to create biomaterials. Bioplastics, however, are less clearly defined. European Bioplastics and the Plastics Industry Association state that bioplastics are 'biobased, biodegradable, or both', which means that bioplastics can still be derived from fossil fuels as long as they’re considered biodegradable. Fossil fuel-based biodegradable plastics include PBAT (polybutylene adipate terephthalate) and PCL (polycaprolactone).
Even when bioplastics are made from natural resources like corn, sugar cane and cassava, they’re manufactured very differently to biomaterials. Crucially, biomaterials are processed without chemical modification to retain their ‘bio’ status, allowing them to compost naturally at the end of life. Mycelium is mixed with agricultural waste and grown in moulds by the likes of Wildsmith Skin and Biohm, wood pulp can be combined with water or compacted using heat and pressure to form strong Moulded packaging , and membrane-forming molecules can be extracted from food waste to create edible, invisible coatings.
Bioplastics, meanwhile, are synthesised and polymerised. The most commonly used bio-derived bioplastics are PHA (polyhydroxyalkanoate) and PLA (polylactic acid) and because of the processes they undergo, they are “structurally identical to petroleum-based plastics”, according to the EPA. Navigating and overcoming this ambiguity is crucial for conscientious designers.
Consider an orange peel which protects the fruit and then composts after disposal. Biomaterials mimic this process. They are derived from nature and give back when returned to it, composting and adding vital nutrients like nitrogen, phosphorus, and potassium to the soil. We consider biomaterials such as MIRUM, Xampla, and Edge to be ‘nutrient materials’ due to this circular, reciprocal process.
Bioplastics, on the other hand, can “last in the environment for the same period of time as petroleum-based plastic”. Like conventional plastics, they break down into microplastics and, although in the early stages, some studies have shown that bio-microplastics can absorb more chemical pollutants. Bio or not, the creation of microplastics should be avoided at all costs as they can expose organisms to toxins, block gastrointestinal tracts leading to starvation, pollute drinking water, and move up the food chain when ingested by marine life.
Bioplastics which can be composted (industrially, never at home) can still cause problems. They don’t meet the USDA’s National Organic Program standards, therefore composters who cater to organic farmers can’t process them, and many do not want them. Even when bioplastics are composted, they do not add nutrients to the soil, turning into carbon dioxide, water, or methane and a small amount of biomass. Shockingly, some bioplastics, while plant-based, cannot be composted at all. Coco-Cola’s 'PlantBottle' is a key example.
Separating biomaterials from bioplastics can be tricky, especially as some bioplastic manufacturers use vague descriptors. As you’d imagine, looking out for mentions of PLA or PHA is the simplest way to spot a bioplastic. Durapulp’s moulded pulp products, for instance, use a PLA binder, whereas Cullen’s are 100% pulp-based. Similarly, alt-leather Pinatex features PLA, while MIRUM does not.
Paying attention to the process rather than the source material is also key for separating biomaterials from bioplastics. PHAs are generally made by depriving microbes, which are often genetically modified, of nutrients like nitrogen and oxygen but providing high levels of carbon, causing them to produce granules. PLAs are made from the starch of food-based feedstocks using wet milling, fermentation, and polymerisation. Structurally identical to plastic once processed, bioplastics like Mango Materials’ YOPP Pellets can be injection moulded and extruded in the same manner as any other plastic.
End of life treatments are another clue. While bioplastics must be sent to plastic recycling, industrial composting or landfill, many biomaterials can be cold composted. Biohm’s food waste-and mycelium-based biomaterials will break down naturally as they are made with an organic binder, so too will Haeckels’ Bio Restore Membrane eye mask which is grown-to-order from seaweed.
Without a single, accepted definition, bioplastics as a category of materials are a broad church, and this ambiguity allows manufacturers to make their own definition, diluting understanding. While you would rightly expect they are derived from nature, it’s not necessarily the case and you could find yourself working with a material that is biodegradable yet partially or fully made from fossil fuels. Looking beyond the name and the impressive-sounding properties to the source material is essential in navigating this new materials landscape.
Bio or not, plastic is plastic and all types should be considered with the same caution. Decoupling plastics from fossil fuels (when they are indeed bio-based) is undoubtedly a positive step. But if you make a product from corn and it’s still destined to languish in landfill or pollute the ocean with microplastics, it undermines meaningful progress no matter how good your initial intentions.
Of course, no one can guarantee that every compostable material will make it to compost but bioplastics form a host of extra barriers. Firstly, the fact that some are compostable and some aren’t leads to consumer confusion which can give rise to ‘wishcycling’ and materials ending up in the wrong waste streams. Secondly, there simply aren’t enough industrial composting facilities to handle the exponential rise of bioplastics, with just 27% of the US population having access to some kind of composting programme, and not all of those accepting compostable packaging. And finally, many of the facilities that do exist simply don’t want them and will send them to landfill to avoid contaminating their product.
