SGS green marks Series | Are your plastic bags really biodegradable?

It is estimated globally we use five trillion plastic bags a year, which equates to 160,000 a second. Each plastic bag with take between 500 and 1,000 years to break down and yet, on average, it will only be used for 12 minutes. 

Many of these bags end up in landfills and our oceans. In 2018, the International Coastal Cleanup recovered 1.9 million grocery and other plastic bags from beaches, but this is just a small percentage of the overall problem.  It is estimated there are already between 50-75 trillion pieces of plastic in our oceans, and it is thought by 2050 plastic will exceed the total weight of fish in our oceans. 

A better and more sustainable alternative is for bags and other plastic products to be made in a way that allows them to biodegrade. 

Consumers demand change

Manufacturers, retailers, and government departments responded with a range of long-term initiatives, such as the UK Plastic Pact which contains a pledge to have 100% of all plastic to be reusable, recyclable, or compostable by 2025. The UK Government also set a target of zero avoidable plastic waste by 2042.  

Consumers, retailers, manufacturers, and governments are now all aware of the need to reduce the use of fossil fuel-based plastics and replace them with more sustainable options. Biodegradable plastics make a sensible alternative when it is not possible to reduce, reuse or recycle.

What is biodegradable plastic?

Made from a wide variety of different raw materials, including cellulose, starch, soy, natural fibers, and lignin, biodegradable plastics do not borrow their properties from the raw material, unlike traditional plastic. Instead, their properties come from the polymer’s chemical arrangement.

Products made from biodegradable plastic, such as grocery bags, will break down in controlled environments or through the use of enzyme-assisted mechanisms. They are transformed into their organic constituents – polymers and organic additives – mainly carbon dioxide, water, mineral salts, and microbial biomass, without adding to the growing levels of plastic pollution already in the environment.

A subset of biodegradable plastics is compostable plastic. These will break down during composting to create a nutrient-rich product, whereas biodegradable plastics degrade in landfills and glycolytic digesters. It should be remembered that all compostable plastics are biodegradable but not all biodegradable plastics are compostable. 

Advantages of biodegradable plastics

Biodegradable plastics can break down up to 1,000 times faster than traditional plastics, thereby reducing the levels of landfills. They also use significantly less energy during manufacturing – for example, a corn-based polymer might consume 65% less energy than the same petroleum polymer. 

In addition, biodegradable plastic production emits less carbon dioxide and greenhouse gases. They are also less toxic, meaning if they are degrading in landfill, they are not polluting the environment. 

Risk of greenwashing

There are clear advantages to using biodegradable plastics over fossil-fuel-based plastics. However, a significant disadvantage is that they cost more to produce. Therefore, there is an opportunity for greenwashing – claiming a product is biodegradable when it is not. 

Claims of biodegradability must therefore be precise. They need to clearly state the conditions under which the property of biodegradability will apply. Without this, there is a risk manufacturers, brands and consumers will think they are operating more sustainably when in reality they are not. 

Addressing the problem

SGS Biodegradability certification helps businesses demonstrate the validity of their biodegradability attribute claims. It can be applied to a wide range of products made from biodegradable plastic, such as grocery bags, plant seedling containers, and geotextiles. 

Products are tested in line with internationally recognized standards:

• ISO 14855-1 – determination of the ultimate aerobic biodegradability of plastic materials under controlled composting conditions
• ASTM D5338 – standard test method for determining aerobic biodegradation of plastic materials under controlled composting conditions, incorporating thermophilic temperatures
• GB/T 19277.1 – determination of the ultimate aerobic biodegradability of plastic materials under controlled composting conditions

The product or material being tested must have a minimum biodegradability level of at least 80% over a maximum period of 180 days to be considered compliant with the requirements of the certification scheme. 

Once it is clear the product conforms to the requirements for biodegradability, it is certified for a period of three years, with surveillance testing. Certified products and materials can then display the internationally recognized SGS Biodegradability green mark. 

SGS green marks

SGS green marks demonstrate the validity of environmental attribute claims such as biodegradability, industrial compostable, biobased, hazardous substances assessed, recycled content, PVC free, PFAS assessed, product carbon footprint, and product carbon reduced. They bring trust to markets that have up until now been at risk of greenwashing.

Such green marks contain details of the environmental claim, the standard(s) it has been assessed against (ISO 14855-1, ASTM D5338, and GB/T 19277.1 for biodegradability), and a QR code that enables the consumer to verify the label and its claim. 

With the expected increase in the production of biodegradable plastics to a projected 4.605 million metric tons in 2028, it is vital for businesses to know the products they are buying conform to accepted standards.  Biodegradability certification and the SGS Green Mark are ideal ways to build a brand’s reputation while encouraging the use of plastics that are better for the environment. 

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