Crustex: Creating Chitosan Fibres to Solve the Microplastic Pollution Problem
What are Microplastics and Why are They an Issue?
Microplastics are miniscule pieces of plastic which have become a concerning pollutant to the environment. These microplastics accumulate in soil, water bodies, and even air, where they remain for hundreds, maybe even thousands of years without degrading, posing a threat to wildlife and marine animals that often injest this harmful pollutant. The toxins in these microplastics can then leach into the tissues of these animals, potentially entering the food chain and posing risks to human health. They originate from a variety of sources, include the breakdown of larger plastic items, microbeads in personal care products, care tires, and most importantly, synthetic fibres.
The amount of microplastics in the world is becoming a huge problem, to the point where our food and water contains more plastics than ever before. Nearly 40% of the ocean is swirling with plastics and cleaning and recycling efforts will not be enough to fix it. At the current rate, the amount of plastics in the ocean will overpopulate the amount of fish by 2050. This issue needs to addressed from its source, we need to understand how plastic is getting into the ocean and where it is coming from.
About 700 000 tonnes of microplastics come from our washing machines, coming from each load when we wash synthetic textiles. This includes polyester, which makes up the majority of our clothing, along with nylon, acrylic and elastane. The fashion industry loves them because they’re cheap and easy to produce, but these compromises are becoming detrimental to our environment.
“Microfibres are thinner than a human hair and are often invisible to the naked eye. They are released into the air and our wastewater systems, and from there into our rivers and oceans.”
Not only do these microplastics disperse into the oceans, they also hold onto toxic chemicals from detergents, posing a major risk for aquatic species. This also affects all animals who eat these species and drink water — meaning almost every animal on Earth is affected — including us, as humans. This contamination can lead to health issues including infertility, poisoning, and genetic disruption.
What are Current Solutions to this Problem?
Currently, organizations are recommending to combat this issue by adopting new habits such as: using laundry filters, using your washing machine less, using cold water and using tightly woven and natural textiles. These solutions are not making enough of an impact. Why? Installing filters into your laundry machines doesn’t prevent the creation of microplastics. Using cold water and washing less only reduces the amount of microfibres released into the ocean minimally. These solutions do not address the root of the problem, and are going to make less of an impact as the textile industry grows.
Natural synthetics are also encouraged, however, these textiles also come with environmental costs. Producing a single cotton t-shirt uses 2 7000 L of fresh water, which is enough drinking water for one person three years. The cotton industry contributes to pesticide runoff and toxicity, and cotton farming is responsible for 11% of global pesticide use, and 25% of global insecticide use. Wool is much higher in greenhouse gas emissions and has the highest global warming potential compared to other natural fibres. The textile industry is only going to grow, causing our environment to be at an even greater risk.
There are also bio-synthetic fibres which are being researched and developed, including fibres derived from corn starch (produces PLA Fiber), cellulose (produces lyocell) and algae. While these bio-polymers are a good start, they have several drawbacks. For example, Polylactic Acid (PLA) Fibre is less durable compared to traditional synthetic fibres. Lyocell requires intensive chemical processing, harming the environment in its own way. The production of lyocell also relies on sustainably harvested wood pulp, taking even more of our non-renewable resource which is needed for many other industries. Our solution, Crustex, solves all these problems. Crustex fibres have 2–3x greater tensile strength than polyester and uses crustacean shell waste, meaning it not only doesn’t take away from our non-renewable resources, but utilizes something that would otherwise be wasted. The process of producing Crustex fibres is also environmentally sound as it does not use harsh chemicals that can not be disposed of safely.
Introducing Crustex
Unlike natural fibres such as cotton and wool, bio-synthetic fibres are naturally derived and produced using biological processes, but are not directly harvested from nature. Instead, they are created by modifying natural materials through biotechnology. We, at Crustex, are looking to use bio-synthetic materials to create more eco-friendly clothing that will eradicate any need for natural and synthetic fibres. We are doing this by modifying chitin into chitosan, a sustainable material derived from crustacean shells, which are waste products of the seafood industry. Chitosan has existed for years, but recently Crustex has found that it can be used to make fibres with similar properties to polyester. Using chitosan fibres is beneficial as they are found to have greater tensile strength, and are derived from materials that would otherwise be completely discarded. Chitosan also biodegrades 520x faster than polyester, as polyester takes 20 years to biodegrade and chitosan would take only two weeks.
Every year, the quantity of crustacean shell waste discarded ranges between 6 and 8 million tonnes. These crustacean shells contain chitin, an amino polysaccharide, which is the second most abundant natural polymer on the earth behind only cellulose. Chitin comes in different forms from crustacean shells and fungi. Its most stable and common form is α-chitin, which is a type of carbohydrate (polysaccharide). Once chitin is attained by crushing the crustacean shells, it goes through a two-step process. Demineralization, which removes calcium carbonate and calcium phosphate using strong acids, and deproteinization, which eliminates proteins adhering to the chitin by using a strong base such as NaOH (sodium hydroxide) at elevated temperatures.
This extracted chitin then goes through a deacetylation process, which is the critical step that transforms chitin into chitosan. Through this process, chitosan gains cationic characteristics, and is easier to establish thin films, exhibits antimicrobial properties, biodegradability, and biocompatibility. Chitosan is then put through a wet-spinning process, after which fibres are refined and are ready to become textiles.
These fibres can be woven into other more common materials such as cotton, wool, or polyester to enhance certain properties of the fabric such as durability, moisture management, and antibacterial properties. It could also be used as a coating onto fabrics, helping with their longevity and functionality. Chitosan could even be used for certain types of disposable or short-term use items such as medical textiles, wound dressings, or protective gear, due to its biodegradability. Our goal is to work towards a future in which microplastics from the textile industry become a thing of the past, so that we can save our oceans and improve the health of both our planet, and we, who live within it.
How does this process actually work?
I. Extraction
First, the chitin needs to be extracted from the exoskeleton of crustaceans. This is done by drying crustacean shells in the oven, and then pulverizing them into a fine powder using a grinder. Once a powder is produced, there could be potential discolouring with the powder having a red undertone, for which an Oxalic acid and Potassium Permanganate (KMnO4) solution could be used. The next step is to use deep eutectic solvents (DESs). These deep eutectic solvents are composed of a hydrogen bond donor (HBD) and a hydrogen bond acceptor (HBA). The HBA and HBD are heated and mix together through magnetic stirring to create a homogenous and transparent eutectic mixture that has a lower melting point than either of the individual components. These molecules arrange themselves in a specific way, forming a network of hydrogen bonds. This unique structure is what gives DESs its solvent properties, allowing it to dissolve a wide range of compounds, including chitin.
The crustacean shells are then treated with citric acid (usually hydrochloric or acetic acid, with a concentration ~ 10%) for demineralization. Demineralization involves the removal of mineral components from chitin, mainly the removal of calcium carbonate. This process helps DESs weaken the network between chitin and proteins more easily. The pretreated demineralized samples of crustacean shells are then dispersed in DESs, and eventually get dissolved into the solution. Centrifugation is then used to separate the chitin and DESs, by spinning the molecules around an axis at high speeds. The chitin is then gathered and rinsed with distilled water until a neutral pH is obtained. Any leftover liquid from the centrifugation (supernatant) can then be collected and reused. The last part of this step is to dry the chitin in an oven.
II. Deacetylation
Deacetylation is the removal of acetyl groups (-COCH3). Chitin is primarily composed of repeating units of a sugar molecule called N-acetylglucosamine. Each N-acetylglucosamine unit consists of two main functional groups: an acetyl group (-COCH3) and an amine group (-NH2). In the deacetylation process, chitin is treated with an alkaline solution, typically sodium hydroxide (NaOH) or potassium hydroxide (KOH), causing the acetyl groups to be removed from the chitin molecule, leaving behind amino groups. This results in the formation of chitosan, which has a higher concentration of amino groups compared to chitin. The reaction mixture is then cooled and kept frozen in an ultra-freezer for 24 hours, after which its temperature is raised again to 115 degrees, and the reaction proceeds for 4–6 hours through mixing and agitation systems which increase the rate of the reaction. The resulting chitosan is then filtered and washed with distilled water until a neutral pH is obtained, after which it is dried in an oven.
III. Dissolving Chitosan to Produce Dope
Chitosan is typically insoluble in most organic solvents. Therefore, chitosan is often dissolved in acetic acid (with concentrations between 1 and 10%, with a pH below 6) with mechanical agitation or heating being used to aid in the dissolution process. The acetic acid then pronates (provides a proton to) the amino groups (-NH2) in chitosan, making it soluble by forcing the chitosan molecules to interact and form hydrogen bonds with each other. This helps create a homogenous chitosan solution, known as “dope”. By forcing the chitosan molecules to form hydrogen bonds, the chitosan is forced to activate elicit capabilities, enhancing its ability to be drawn out or elongated into fibres. The creation of dope is also required to activate anti-microbial properties.
IV. Wet Spinning
Once “dope” has been produced, the solution is then put into a wet spinning machine. The dope itself would be spinning, and be put through a pump which would push it towards a spinneret. The spinneret has many tiny holes through which the fluid is pumped in order to produce filaments. The spinneret extrudes the solution through a coagulating bath. The coagulating bath is a non-solvent that is miscible, meaning it forms a homogenous mixture when combined with the spinning solution. This causes the polymer to precipitate or coagulate (clump) into a solid fibre form. The fibre is then oriented, as there is a take-up device that gathers the fibres, organizing and lengthening them.
V. Refining the Fibres and Creating Textiles
Once the fibres have been extruded and oriented through the wet spinning process, the semi-finished fibres then undergo further treatment where they are mechanically stretched and aligned. The fibres are also dried to remove excess moisture once they have passed through the coagulating bath.
Once all these steps have occurred, the result is now a usable fibre made from the waste of crustacean shells, which can then be spun and stored to be woven or knitted into various textiles to be used for clothing. The properties for dyeing this clothing and utilizing it are very similar to polyester, meaning no other changes to the textile process is required.
Next Steps
I. Our Impact
The microplastics in our oceans have a great environmental impact as they can effect marine organisms, and accumulate while being transferred up the food chain, even affecting humans. They can disrupt marine ecosystems, reduce biodiversity, alter habitats, and contaminate out food, water, and even the air we breathe. Through Crustex and our chitosan fibres, we will be able to create fabrics that are 2–3x more resistant to tensile stress compared to polyester, leading to longer lasting clothing. These new fabrics will also take 520x less time to biodegrade, and once scaled, we will be able to decrease the amount of microplastics released into the ocean during washing and disposal by 100%.
I. Benefits
There are several benefits when using bio-synthetic fibres for clothing. Environmentally, we are producing a biodegradable fibre which can be easily produced without depleting our resources or adding any more pollution to our oceans. Secondly, chitosan can be sustainably sourced from waste materials generated by the seafood industry, not only helping reduce microplastics in the ocean but also minimizing waste generation and maximizing resource efficiency, promoting a circular economy. Secondly, the production of chitosan fibres typically involves environmentally friendly processes. The DESs can be reused multiple times until they have to be disposed of. Other parts of this process do not require harsh chemicals, and use things such as acetic acid and sodium hydroxide, which are far easier to dispose of compared to the large amounts of water, energy, and harmful chemicals you need to dispose of due to synthetic textile production.
II. Cost
When calculating the cost to produce chitosan fabrics, we found that there would be a base cost of $53 per shirt. This price can vary depending on factors such as its quality, degree of deacetylation and molecular weight (average size of polymer chains, higher meaning better mechanical properties and functional performance).
III. Scaling
Although this technology is still in its early stages, there is a lot of research being done to reduce the time needed to produce the fabric as well as the cost of making chitosan. Initially, the fabric would need to be introduced through being woven into other materials and textiles. This would still have its own environmental benefits. We then plan to use Crustex fibres for disposable clothing such as medical textiles, wound dressings or protective gear, as its biodegradability would help minimize a lot of the pollution caused by these clothes. Finally, we hope for chitosan to become a fabric that is accessible to everybody, making it both better for the planet and better for you.
Conclusion
Our world is suffering due to microplastic pollution, and this problem is only going to get worse through increased textile production. Our vision is to create a world in which, 20 years into the future, marine biodiversity is thriving, and a world where we don’t have to worry about increasing levels of microplastic contamination in our food, water, and air. This is an effective solution to the problem of microplastic pollution, a problem whose root cause needs to be addressed sooner rather than later. Our solution of using bio-synthetic fibres to both increase textile durability and biodegradability has the potential to make a substantial impact on the future of our planet.
If this article piqued your interest in Crustex and you’d like to learn more, check out our website at crustex.typedream.app.
Crustex co-founders: Inayat Kang, Neeor Alam, Samir Sharma, & Shahmeen Sarmad
