By Mary Hearty

In an effort to bring an end to plastic pollution as well as marine litter especially those made from fossil fuels, the United nations Environment Programme (UNEP) has suggested the development of alternative materials through green and sustainable chemistry innovation framework.

The organization acknowledged this framework in their newly published 2021 report titled: From Pollution to Solution: Global Assessment of Marine Litter and Plastic Pollution.

In the report, UNEP explained that development of alternative materials using green chemistry fosters a vision of green and sustainable chemistry.

Also, it emphasizes the potential for the global chemical industry to become fully aligned with the environmental, social and economic dimensions of sustainable development by creating greener and more sustainable chemistry innovations.

At the same time, addressing toxic and persistent legacies associated with past chemistries in order to minimize adverse impacts across the entire life cycle of chemicals and products.

UNEP noted: “A key part of the framework is to keep processes as simple as possible, with a minimal number of steps, auxiliaries, energy, and unit operations, to improve the environmental performance of manufacturing materials.”

According to UNEP, green and sustainable chemistry innovation can play an important role in advancing circularity- a principle that used products serve as raw materials for new products; and provide significant improvements to plastics derived from fossil-fuel feed stocks.

This is by designing molecules, materials and products that can be more easily recycled and up-cycled than those currently on the market.

For instance, UNEP stated: “This can be achieved by eliminating chemicals of concern in products that currently prevent sound recovery and recycling especially those that are intentionally released to the environment and have open-environmental applications such as pesticides, cosmetics, biocides, or pharmaceuticals.”

Green and sustainable chemistry innovation could help design their molecules and materials that rapidly mineralize in the environment while retaining desired functions.

UNEP said the demand of plastics continues to grow, with the size of the global plastic market in 2020 estimated to be around US$ 580 billion compared to an estimated US$ 502 billion in 2016.

At the same time, it is estimated that less than 10% of the plastics ever produced have been recycled. One of the main reasons for current low recycling rates is lack of information about the constituents of plastic products, which can complicate the recycling potential of plastics hence loss of quality through the mixing of waste streams.

“For example, thermoplastics can be melted when heated, hardened when cooled, and reheated, reshaped and frozen repeatedly while thermosets such as polyurethane, vinyl ester and a range of resins cannot be re-melted and reformed because they undergo a chemical change when heated,” UNEP reported.

Additionally, the many hundreds of additives can alter the recycling potential of plastics as well and may restrict their reuse due to the likely release of hazardous chemicals into the environment.

These limitations ultimately cause millions of tons of plastic waste to be lost to the environment or shipped thousands of kilometres to destinations where it is generally burned or dumped in waterways, UNEP explained.

Currently, plastic recycling is undertaken using mechanical and chemical processes. Mechanical recycling is used for non-fibre plastic, and increasingly for recycled polyester yarns.

This process involves grinding up bottles into flakes, washing them, and then melting them back into new polyester chips. Chemical recycling, which combines various plastic-to-fuel and plastic-to- plastic technologies, turns plastic into liquids or gases, which can be used to make new plastic.

Unfortunately, there are concerns about plastic-to-fuel processes because they perpetuate the burning of fossil fuels which emit carbon dioxide, a greenhouse gas into the atmosphere, causing global warming.

According to the Intergovernmental Panel on Climate Change (IPCC), emissions from fossil fuels are the dominant cause of global warming. In 2018, 89% of global CO2 emissions came from fossil fuels and industry.

Regarding plastic-to-plastic processes or “repolymerization”, UNEP said it is technically challenging to scale up sufficiently to make it financially viable, although industrial examples are emerging.

Therefore, UNEP recommended green chemistry as its contribution to many end markets where plastics are currently used is significant.

The organization encouraged innovations in transportation industry, the construction industry, food and packaging, and waste management to take this into account.

Even amid the Covid-19 crisis, the global green chemical market has been estimated at US$ 93.7 billion in 2020 and is projected to reach a revised size of US$ 167.1 billion by 2027, growing at a compound annual growth rate close to 10 per cent to reach US$ 77.4 billion by 2027.

As yet only very small volumes of bio-sourced and bio-based plastics are being produced. Bio-based plastics are fully or partially made from plants or biological resources, rather than fossil raw materials.

Commonly used raw materials to produce these renewable feedstock for plastic production include corn stalks, sugarcane stems and cellulose, and increasingly also various oils and fats from renewable sources.

Although, it is important to examine the full life cycle of bio-based plastics, to ensure that they are beneficial to the environment beyond the reduction in use of fossil resources. This includes littering and changes in land use.

This is because some bio-based plastics, such as, drop-in plastics have identical chemical structures and properties to conventional plastics. These plastics are not biodegradable, and they are often used in applications in which durability is a desired feature. They include bottles, chairs and even carpets.

UNEP reported that in 2018, 2.11 million metric tons were produced, less than 1% of the total volume of plastics produced. Of this amount, 43% was biodegradable and 30% was both bio-sourced and biodegradable.

However, the market size for renewable energy from bio-based feedstocks is much larger than that for bio-based plastics. Thus, for advanced bio-based plastic pathways to take off, they must not only prove themselves technically and economically feasible.

A number of factors need to be considered in shifting towards more bio-based feedstocks. For instance, there is heavy reliance on agriculture, with bio-based crops tending to score poorly on other environmental metrics such as ozone depletion, acidification, eutrophication, water use and food security.

In terms of energy substitution, UNEP noted there is no change in the final resin produced and bio-based polymers can substitute across the market without any changes to downstream production methods or product functionality.

While biodegradability may be an advantage for polylactic acid and some other bio-based plastics in terms of reducing the volumes of waste going to landfills, UNEP said few cities and communities have the infrastructure required for composting under the correct conditions.  so many organizations using compostable biopolymers are likely to continue to send their waste to landfills.

This may present a major problem for bio-based as well as biodegradable plastics more generally. UNEP also states that there is significant confusion among consumers about recyclability and biodegradability, especially as descriptions such as “degradable”, “oxo- degradable”, “oxo-biodegradable” and “landfill degradable” have been used to promote products made with traditional fossil-fuel based plastics, supplemented with specific additives promoting degradability.

Overall, replacing one disposable product like those made of plastic with another disposable product made of a different material like paper or biodegradable plastic is only likely to transfer the environmental burden and create other problems.

Further, to avoid burden shifting between the environmental and the social dimension, UNEP said it is important to shift the focus of manufacturers towards the production of more circular and sustainable commodities.

Additionally, building circularity in support of sustainable consumption and production objectives across the life cycle of plastics means going beyond the 3Rs (Reduce, Reuse and Recycle), to 5Rs with Recover and Redesign, and further to 7Rs with Refuse and Rethink.

Other patterns of Rs have also been designed for circularity, such as Receive, Recycle, Repair, Refill, Rent and Resell. These are now being used to deliver new kinds of services; for example short-term loans of branded products can that be reused by different consumers include luxury fashion to furniture and toys.

Finally, an important part of building circularity for plastics is improving the traceability of products and their constituent parts. UNEP noted that green chemistry can provide innovative molecules that ensure traceability and can be used to create product digital passports such as composition of products, components, and processes.

These, coupled with block-chain technologies, can enable end-to-end traceability of supply chains. When a product failure occurs, or when the product is to be recycled, the molecules and digital passport can provide the information needed to identify the suppliers or the constituent chemicals.