Plastics

21/09/2017

This article presents seaweed-based bioplastics, aiming to solve the plastic waste crisis, introduced here.

Tommorow’s packaging: seaweed as raw material

Brown seaweed abounds in the seas and oceans. There are multiple environmental interests to using them: seaweed grows naturally, doesn’t require fertiliser or pesticide and captures CO2 in water. Moreover, seaweed-based products are entirely compostable and even act as natural fertiliser. Unlike using terrestrial plants, often destined to the food industry, using seaweed to make packaging does not create a competition with food production.

Ooho, the edible water bubble

The first project from Skipping Rocks Lab, Ooho, is a water-containing biodegradable capsule made from seaweed. Ooho is edible: you can either eat it whole, or pierce it to drink the water it holds. Compared to using PET bottles, this solution produces 5 times less CO2 and consumes 9 times less energy. The mouthful-sized bubbles currently contain 40mL of water.

How does it work?

The principle of Ooho rests on making a sodium alginate based gel, a food additive commonly used in the food industry. Extracted from seaweed, alginate is a polymer, more precisely a polysaccharide: it is a chain of monomers, in this case two molecules which belong to the sugar family, the mannuronate (M) and the guluronate (G).

In water, in the presence of calcium ions, they form structured networks. Indeed, the alginate is negatively charged, whereas the calcium ions are positively charged, which make them attracted to each other. Moreover, the calcium has two positive charges: one Ca2+ ion can thus link two alginate chains and create a bridge, which generated an spatial arrangement of the chains and forms a complex which is insoluble in water. This is how the gel is formed.

This method, patented in 1942 by William Peschardt (Unilever) and mainly used in gastronomy to make fake caviar, can be used to encapsulate any kind of liquid.

What are the limits?

The lifespan of a bubble is only of a few days – to sell the Ooho in shops, a daily delivery and quick sell is thus required. Moreover, this packaging is less resistant that a traditional bottle, limiting its use to an immediate consumption: it is indeed not possible to transport the bubbles in a bag. For now, this means those bubbles are limited to be used in punctual events, such as festivals, conferences or receptions. Nevertheless, the forthcoming developments could lead to stronger containers with an increased lifespan.

Seaweed-based bioplastics

It is possible to transform polysaccharides not into a gel, but a solid, starting from the same seaweed as for Ooho. Similar to synthetic polymers, the physical properties of the final product depend on the formulation of the sugar chains, their density and potential additives.

Several start-ups and academic laboratories are currently investigating the possibilities of using seaweed to make biopolymers. Founded in 2010, Algopack is specialised in making bioplastics from seaweeds collected along Brittany’s coasts in France. Following a first range of products, Algoblend (a mixture of 50% artificial polymer and 50% natural polymer), Algopack developed a second range of products entirely made with algaes. The process enables them to make granules (similar to those of common plastics) which can be used to make daily items. Such a bioplastic dissolves in water within a few hours, but it is also possible to make it waterproof to make it more resistant and therefore, more durable.

A sneak peek of the Algopack granules, which can be used exactly as classical polymer granules to make items.

In 2016, Algopack was bought by Algaé Innovations, a branch from Lyreco (a group specialised in office supplies). The only information that was since communicated concerned the delay of their new installation. We reached out to the company about it but we haven’t received an answer yet. It is therefore difficult to know if the project is actually continuing.

On the other side, the American company Algix are exploiting the properties of algaes in water treatment centers a well as using them to make bioplastics. Algix’s most recent project, Bloomfoam, consists in making polymer foam from seaweed.

Lastly, in Korea, Professor Park Jin-Byung’s group in the Ewha Womans University recently developed a method enabling them to extract the fatty acids from dried seaweed, that they then transform into carboxylic acid monomers in one chemical step. The question now is whether they will be able to industrialise this solution.

Why are seaweed-based biopolymers biodegradable?

A material made with natural products is not necessarily biodegradable and, as we saw, it is a critical stake to fight against plastic pollution. A material is said to be biodegradable if it can be degraded in the environment (mainly by micro-organisms) into smaller elements that can then be metabolised and therefore naturally recycled in the biosphere.

The Ooho bubbles and seaweed-based bioplastics are polysaccharides. It is a common type of natural polymer, from the same family as cellulose and starch, which are degradable by natural enzymes.

In those polysaccharides, the sugar units are linked together by oxygen atoms. From a chemical point of view, those oxygens constitute a rich environment, that means many reactions are possible around them and, therefore, the polymer degradation is rather easy. In comparison, the polymers from the petrol industry such as PE are made of long carbon chain, an environment considered “chemically poor”: it is difficult to break a carbon/carbon bond and, without extreme temperature and pressure conditions (incineration), there are very few ways to biodegrade such polymers.

As a conclusion, if the production of biobased and/or biodegradable plastics is set to increase in the forthcoming years, especially because of the new laws to protect the environment, companies using seaweed as raw material in an industrial scale are still limited in number and in applications.

The interest of algae is double: they are biobased and their products are biodegradable, their use thus lowers the environmental impact compared to using plastics made from the petrol industry. Only an innovative effort will help expand and democratise their use.

This work is under CC-BY SA licence: