Plastic is incredibly versatile–it’s lightweight, durable, and cheap to produce. It’s no wonder that it has become one of the most commonly used materials in society today. But plastic’s detrimental effects on the environment is no secret and it’s time to find an alternative. In this blog post, we’ll explain what plastic is and the bioinspired materials currently under production to replace it.
Plastics 101 - What are Plastics? How are they made?
Some of the first recorded uses of plastic date back over 3,000 years ago, when ancient civilizations found ways to harness naturally occurring plastics from the environment (e.g. the sap on trees). Since then, plastic production has undergone a significant cultural transformation - no longer being regarded as a natural product but rather as one of the most ubiquitous and unsustainable materials in the modern world.
On an atomic level, plastics are made from a synthetic/semi-synthetic string of polymers (chains of repeating chemical compounds). This molecular structure provides plastics with malleability under heat/pressure, durability, and their trademark versatility, explaining why plastic is so prevalent in a variety of industries. Plastic is created through a process called polymerization - where small molecules (monomers) are chemically bonded through a reaction to create a long string of such molecules (polymers). These monomers that create plastic are derived from crude oil and natural gas from the ground, which relies on harmful practices of extracting fossil fuels. After the raw materials are obtained, they are further broken down into the building blocks of plastics (monomers) at a cracker plant where crude oil and natural gas become ethylene and propylene respectively. In order to begin polymerization, a catalyst is used to induce a chemically binding reaction that links the molecules, forming polymers known as resins (e.g. polyethylene and polypropylene).
The Problem with Plastic
The plastic revolution beginning in the early 20th century has proved to be extremely advantageous for society - bringing on economic growth, efficiency, and numerous engineering developments. Plastic packaging specifically proved to be a huge breakthrough, which allowed for the transportation and conservation of goods. However, as previously explained in the manufacturing process, it is clear that the backbone of plastic production ultimately relies on the extraction and burning of fossil fuels, which contribute to almost two billion tonnes of greenhouse gas being produced from plastic each year.
Another major issue with plastic is its single-use consumption - a specific example being plastic packaging. Although more recycling technology has been developing in recent years in the wake of the climate crisis, 85% of plastic waste is still not recycled and ends up directly in landfills. In fact, plastic waste is so ubiquitous on our Earth that it has started to form its own microbial environment known as the plastisphere. The fear for the upcoming 50 years is the problem of increasing microplastics pollution: the issue being tiny pieces of plastic are showing up everywhere in the environment - in oceans, on the land. They are being consumed by mammals and fish and ending up the food chain.
When a tree falls in the forest, whether it makes a sound is one question. But one question we do know the answer to is what happens to it. Slowly but surely, it decomposes while fungi, pathogens and bateria cause the decay of the materials the tree is made of, mainly cellulose and lignin. When plastics fall in the forest, for example from the pockets of humans, generally no such thing happens. The plastics are immune to decomposition which is why they persist in the biosphere, perhaps in perpetuity.
Plastic Surgery: A Packaging Makeover from Nature
One solution to the plastic crisis lies in nature, with the current research happening in bioplastics: plastic packaging created from bio-based materials. This technology relies on replacing the unrenewable polymer backbone with biopolymers sourced from biological and preferably biodegradable materials. The raw materials used for these polymers are often plant-based from corn starch, sugar, and a variety of agricultural products. For example, polylactic acid (PLA) polyhydroxyalkanoates (PHA) are the most prevalent bioplastic monomers on the market today. PLA is derived from corn and sugar cane while PHA is made from the digestion process of microorganisms.
PLA can break down into lactic acid and carbon dioxide. PHA can break down in the soil to carbon dioxide and water, with the help of microorganisms. The oxygen atom in the backbone and C=O group, which you can observe in their structure, make them different from polymers like polyethylene, and this part of the molecular structure is what helps make them biodegradable.
It is crucial to note though that there are challenges that come along with bioplastics namely they are often less sturdy and they require specific conditions in order to be properly recycled, meaning that bioplastics would need to be sorted separately without the contamination of other plastics. Until biopolymers can become a viable and abundant plastic alternative on the market, scientists must carry out additional research on their complex chemical, physical, and mechanical properties.
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