CO2 Michael Stephen Column Seaweed and Algae

Plastic from Algae and Carbon Dioxide (FREE)

Michael Stephen, an international expert on bioplastics, shares his thoughts and opinion on important issues impacting the bioplastics industry. Today, Michael writes about plastic from algae and carbon dioxide. This is a FREE article.

Plastic from Algae

I hear that a French company, Alternative Plastics, has won the 2021 Carrefour Innovation Prize with their Alg&Bag garbage bag range.  The bags are made in France with Eranova’s bio-polymer made from green algae collected from beaches.  Green algae is an environmental nuisance which pollutes beaches. It is not only an eyesore, but the build-up can be toxic, causing beaches to be closed.

For those who like bioplastics, this is a much better way to make them than by using scarce land and water resources which should be used to grow food. The bags have been designed to be fully recyclable with the existing waste stream of fossil-based polymers, so will not disrupt the recycling process.

I would expect to see the Alg&Bag garbage bags on the shelves of Carrefour supermarkets soon.

Carbon Dioxide

Usually we are trying to reduce CO2 because it is thought to contribute to climate-change, but a recent shortage due to the shut-down of a fertiliser factory in the UK has drawn attention to the positive uses to which this gas can be put.  CO2 is used as an antimicrobial agent, often in combination with nitrogen, to form an anaerobic environment to inhibit aerobic microorganisms.

Raw and cooked meats, fish, ready-meals, and bakery goods may be packed with carbon dioxide at levels between 25-40%, – with the exception of bakery goods and some cheeses where it can be used up to 100%. High concentrations of carbon dioxide can increase the mould-free shelf-life but will not prevent bakery goods becoming stale.

However, CO2 is highly soluble in moisture and fats. Solubility of carbon dioxide in the water phase of foods produces carbonic acid which can increase the acidity of the product resulting in a drop in pH. So, the use of COmay have an undesirable effect on the food.  Also, due to solubility, high levels of carbon dioxide can cause pack collapse. It is normally recommended that a 2:1 gas-to-product ratio is used, but this results in a large empty headspace and producers are criticised for using too much packaging material, and increasing transport and storage costs.

Instead of injecting the pack with CO2 gas, I am told that a better way is to put antimicrobial ingredients into the packaging film itself, so that the microbes cannot survive on the inside surface.  This is also better than spraying or dipping foods with antimicrobial agents, because those agents can migrate into the foods and modify their organoleptic characteristics (taste, texture, odour, etc.). I see that for these reasons Symphony Environmental Technologies has developed an antimicrobial masterbatch which can be included in the packaging film at the point of extrusion. See

Detailed studies have shown no migration of the Actives into foods and no effect on taste, odour, texture, or freshness. It seems that the protection is effective even at higher storage temperatures (e.g. bakery products, up to 45 Celsius).

CO2 is effective against Gram Negative bacteria, but the antimicrobial masterbatch is effective against Gram (+), and Gram (-) Bacteria, Moulds/mildew/Fungi/Yeasts, as well as against algae and viruses. The Actives in the masterbatch are at a low concentration (in some cases in the ppm range) providing a very cost-effective solution.

Symphony’s scientists tell me that the antimicrobial masterbatch can also be used in combination with their oxygen-scavenger technology, as oxygen promotes deterioration of the food.  There are 3 sources of oxygen inside a food package:

a.)     The food itself

b.)    When food is packaged, there is a certain volume of air remaining inside the package. Vacuum-packaging can overcome this problem, but it is expensive, and requires additional equipment and work force.

c.)     Oxygen can penetrate through the macromolecular structure of plastic packaging materials (e.g., polyolefins).

If the Oxygen Scavenger Agent is incorporated into the packaging material, the residual oxygen inside the packaging can be lowered to 0.01% – lower than by using a modified atmosphere (e.g., CO2 or CO2 + N2).

By combining the Oxygen Scavenger Technology with Antimicrobial Technology, the shelf life of food inside the package can be increased – thus reducing food-wastage, without affecting the quality of the food.  If the packaging is made from PE or PP it can also be made biodegradable by including Symphony’s d2w masterbatch, so that it will not lie or float around for decades if it gets into the open environment. 

Michael Stephen

Michael Stephen is a lawyer and was a member of the United Kingdom Parliament, where he served on the Environment Select Committee. When he left Parliament Symphony Environmental Technologies Plc. attracted his attention because of his interest in the environment. He is now Deputy Chairman of Symphony, which is listed on the AIM market of the London Stock Exchange, and is the founder and Chairman of the Oxo-biodegradable Plastics Association.

Earlier Postings in this Column

Interview with Michael Stephen


The opinions expressed here by Michael Stephen and other columnists are their own, not those of

Leave a Reply

%d bloggers like this: