Innovation fights plastic pollution
CSIR data has found South Africa’s rising population and increased consumption means that, without urgent action, plastic pollution is set to almost double to 865000 tonnes in 2040 from 491000 tonnes in 2020.
Globally, more than eight million tonnes of single-use plastics are dumped in landfills or the oceans each year, where they persist for hundreds of years.
According to the CSIR, biobased materials, derived from renewable sources, present a solution to plastic pollution, reducing greenhouse gas emissions and contributing to a circular plastics economy.
“It’s been shown the greenhouse gas emissions when it comes to plantbased polymers is about 75% less than conventional plastics,” John said.
While more expensive than traditional plastic, “we go to the companies making these [conventional plastic] products and ask them to do runs on our materials to show them these can be made on the industrial line you have, that you don’t need to make any changes or any capital expenditure investments to adopt this material”.
In the agricultural sector, farmers who plant seeds for strawberries, lettuce and sweetcorn, for example, lay down plastic mulch film, to help crop growth and to reduce evaporation.
“The problem is, after the crop is harvested, the farmers have to physically remove this and then prepare the field for the next cycle. That’s quite expensive.
“What we thought of was mulch films from plant-based biopolymers that are soil biodegradable so that, after your crop is harvested, that mulch film will biodegrade into the soil, so then the farmers don’t have to go through the process of additional labour of getting this all out and being ready for the next cycle.”
John said plastic agricultural mulch films are thin and can slowly disintegrate, forming microplastics that can pollute the soil and which can be easily transported elsewhere.
She and her team went a step further. “Crops have different life cycles. Some biopolymers might biodegrade eight months in the soil and, if your crop is a short-term crop and gets harvested within three months, then it doesn’t serve its purpose.
“We have developed mulch films with additives that can accelerate or retard the biodegradation, depending on the life cycle of the crop. If it’s a short-term crop, like three or four months, you have a mulch that will also biodegrade at the same time.”
The CSIR is working with the Agricultural Research Council and the University of Nigeria, which are doing field trials.
Last year, the UN Industrial Development Organisation (Unido) and the government of Japan donated biodegradation assessment laboratory equipment to the CSIR. It hosts the only laboratory in Africa equipped to test and verify imported or locally produced products that are being touted as biodegradable.
“The Unido-funded testing laboratory is capable of establishing the conditions and timeframes for the biodegradation of materials,” John said. “Tests can be performed under different conditions — aerobic (compost, soil, freshwater and marine) and anaerobic.”
Several products are being marketed as more environmentally friendly alternatives to conventional plastics. “Without evidence from testing and life-cycle analyses, businesses can misguide consumers. Industries can use the CSIR facilities for this.”
The CSIR is working with the South African Bureau of Standards to develop national standards for home compostability.
There is no mandatory legislation specific to the material properties of biodegradable and compostable plastics in South Africa, according to a 2020 review of biodegradable and compostable packaging.
“We test if a product is really biodegradable because some people just spread lies to claim that their products are biodegradable,” said senior researcher Asanda Mtibe, who explained that they use internationally developed standards. “For example, for home compostability, there’s a standard that was formulated in Australia, so we are testing based on the available standards.
“If you’re claiming your material can compost in industrial compost, then we follow that standard, which says in six months, 90% of your material should have biodegraded.
“If you claim your material is compostable, but when we test it here, 90% of material does not biodegrade in six months, then it’s a false claim.”
John said the CSIR’S compostability assessment comprises mineralisation, chemical characterisation, disintegration and eco-toxicity tests.
There are different aspects to biodegradation. “There’s disintegration where a material disintegrates into smaller fragments; then there’s mineralisation where 90% of the carbon in the material should be converted to carbon dioxide.”
The eco-toxicity tests determine that “whatever is left behind after biodegradation does not contain any toxic elements and it is suitable for plant growth … These are the three aspects that we need to do to claim that a material is biodegradable,” says John.
“What we see right now is that most people do the disintegration, where it’s just fragmenting into smaller particles, and they don’t do the mineralisation because they don’t have the capability to do it, and then they claim it is biodegradable.”
But disintegration is not biodegradation. “It just disintegrates into smaller particles and leads to the formation of microplastics and nanoplastics. It is not environmentally friendly because this can accumulate in the food chain and gets transported into different environments. You have all of these reports finding microplastics in human blood.”
There is a misconception, too, that compostable and biodegradable materials can be “discarded anywhere and it will biodegrade”.
“Biopolymers biodegrade under specific conditions and that depends on the type of biopolymer. When something is biodegradable, you have to follow it up with two more aspects. One is the conditions of biodegradation — does it biodegrade in soil, in compost or in water — and also, the timeframes. How long does it take to biodegrade?” she says.
“Without this information, to say something is biodegradable is actually an incomplete sentence.”