A step towards a sustainable future

As the sixth-most-produced and -used polymer globally with an annual production of around 25 million tonnes (the global plastics and polymer market was estimated to account for 460m/t in 2024), polyurethanes are facing challenges regarding recycling and end-of-life disposal. 

About 52% of global PU products are manufactured as foams (flexible and rigid), and the rest are used in CASE (coatings, adhesives, sealants and elastomers) and binders; this makes their recycling and disposal very complicated.

Bio-based isocyanates using natural oils, lignin, amino acids, algae, saccharides and cashew nutshell oil, to name a few, are available in the market. The bio-based content in the products is measured using the mass balance approach, allowing manufacturers to attribute the final isocyanate product as bio-based even though the renewable feedstock is mixed with fossil-based feedstock.    

Mass balance reduces the carbon footprint by 60-70%, and major manufacturers like BASF, Huntsman, Evonik and Covestro now have portfolios of mass balance-certified isocyanates in their ranges.

Similarly, bio-based polyols are also manufactured using many similar feedstocks to isocyanates, but natural oil polyols are the most prevalent ones. Polyols based on a range of vegetable oils – soya, castor, palm and rapeseed – are readily available in the market, especially in the Europe and Americas regions. However, natural oils also face competition from other sources of ‘natural’ polyols, such as those made from sugars (sorbitol and sucrose), or from bio-based diols and diacids, including bio-succinic acid.

In the PU industry, natural oil polymers (NOPs) are used in flexible and rigid foams (furnishings and insulation, respectively), elastomers, sealants, paints and coatings. However, consumption levels are still small in Western Europe and virtually negligible in Eastern Europe and the Middle East. Raw material producers in Europe seem to have a propensity for recycled and carbon dioxide-based polyols, as opposed to NOPs. 

In Asia Pacific (APAC), NOPs based on soybean, castor and palm oil account for the largest proportion of sustainable polyols due to the abundant vegetable oil feedstocks available in the region. Competing bio-polyol technologies include those based on sugars and bio-based diols like 1,3-propanediol and 1,4-butanediol and diacids like succinic acid. NOPs have attracted attention from the PU industry as a greener alternative to synthetic polyols due to the cost savings incurred when importing petroleum-derived polyols.

In China, bio-based PU foam has struggled to gain market share due to its lack of price advantage and custom requests. Domestic suppliers struggle to provide consistent quality products, and there is limited consumption of soybean oil polyols in the country.
 

There are still limitations on the use of bio-based polyols due to difficulties encountered in their incorporation into urethane formulations. Levels above the established limits typically lead to poor foam compression, poor stability, higher risk of tearing and an undesirable odour.

Polyols from bio-based feedstock such as soybean oil, linseed oil, castor oil and cashew nutshell oil are being produced in North America. These polyols are used in automotive interior components, spray PU foam, flexible PU foam slabstock, elastomers and footwear components.

The contribution of NOPs to the overall polyols used for PU production was around 3% in 2024, and it is expected to increase its share to 12% up to 2032.

Flexible foam offers the largest potential for NOPs. However, customers are reluctant to pay the premium price for NOP-derived products, which can be up to four times higher than conventional polyols and create processing issues. 

The second stage of the sustainable PU initiative is effective recycling of PU foams. Mechanical recycling is the easiest option for the recycling of PU. For this process, the foam is reduced to flocks and used for other end uses, such as carpet backing, NVH foam and acoustic insulation (known as bonded foam); however, this demand is relatively low compared with standard slabstock foam, and a considerable amount of waste is still accumulated. This kind of recycling is called open-loop recycling because it cannot be used to produce new products.

In Europe, numerous institutes and companies are involved in research projects to find ways to reuse foam via chemical (closed-loop) recycling. The technology has been in use in Europe since 2013 for post-industrial waste and has now evolved to be able to recycle post-consumer foams. Several industrial-scale or pilot plants for chemical recycling of flexible PU foam have been planned or are operational, notably in France, the Netherlands, Spain, Germany and Belgium.

Several major PU raw material companies, including Covestro, Dow, BASF and Evonik, have developed pilot facilities in Europe for the collection and chemical recycling of furniture and mattress foam, but activity in North America remains limited. 

In the APAC region, closed-loop or chemical recycling is still at the R&D stage.

The need for waste management, environmental regulations and attempts to reduce fossil fuel dependence will be the major drivers for PU sustainability.