One need only look out their window to see first-hand evidence of the plastics pollution we currently face. It was reported in 2017 (Geyer, Sci. Adv.) that since 1950 around 6300 million metric tonnes of plastic waste have been created. Of this enormous amount of waste, a mere 9% has been recycled and 12% incinerated, with the remaining 79% ending up in landfills or oceans. Despite numerous advantages, many related to energy and resource efficiency, the detrimental effects of “single use” plastics are indisputable, and clearly things need to change with regards to consumer demand and use of these disposable materials.
Chemically speaking and as defined by IUPAC, a plastic is a “polymeric material that may contain other substances to improve performance or reduce costs”. We therefore question the broad classification of single use plastics being ‘bad’ and instead suggest that the issue we face is the bad use of plastics. Even those plastics deemed ‘bad’, like polypropylene and polyethylene, are ideal for the purposes, like disposable bottles, supermarket bags, and plastic packaging, with which they are now associated – it is their impact post use that causes controversy. These plastics, and many others, also have uses inherent to our daily lives with lifetimes of twenty or more years that we cannot discount. Polypropylene is used in thermal undergarments, as well as in reusable plastic containers. Polyethylene makes up many industrial machine components and artificial joints. These subsets of applications offer significant positive impact that more than offsets their current ‘bad’ reputation.
Overcoming the ‘bad use’ of plastics
The necessary shift in our approach to overcoming our bad use of plastics is the responsibility of all those in the plastics chain – the industry, the users, and the government. Luckily this change in mindset is already underway. Users are becoming more conscientious in their use of multiple-use alternatives to common plastic products and the ways in which they recycle waste. Increasing numbers of multinational companies, including Ikea, Coca Cola and McDonalds, have committed to ensuring that their plastics are both recyclable or compostable, and incorporate increasing proportions of recycled plastic. Several government bodies are introducing levies or bans on some of the most problematic plastic items, like bags, straws and microbeads, as well as funding of research towards recyclable alternatives. There is also significant work in many areas of the plastics industry itself to make plastics in more environmentally conscientious ways – whether in the precursors used, many of which are typically petrochemical in origin, in the efficiency of manufacture, or in their ability to be more easily recycled.
Polyurethane – A case study
Polyurethane (PU) is present in our daily lives in more ways than one might expect. This plastic, the third most widely used behind polyolefins and PVC, accounts for approximately 10% of all plastics produced, and is forecast to generate close to $80 billion worldwide by 2021, or 20 million tonnes annually (Ceskaa, 2017). Rigid foams make up the insulation in our walls, which facilitate a decrease in heat loss of ~60% when compared to other insulative materials (Kingspan, 2018). Flexible foams add comfort to our lives in the form of memory foam mattresses. Coatings protect our clothing, wooden floors and vehicles to extend their useful life. Adhesives stop our shoes from falling apart. Elastomers make up the wheels that allow us to open drawers and ride rollercoasters. Simply put, the stability and durability of PU in any one of its forms is essential in protecting us and our essential items from wear and tear and the elements.
Alternatives to PU
The production of PU is an energy and petrochemically intensive process – replacing this material with alternative biodegradable/natural/energetically less demanding materials is a natural initial response. Certainly, one could envisage replacing PU insulation (160 kg CO2 emitted / kgCO2e), with a less carbon intensive material like cork (-155 kgCO2e), glass fibre (8 kgCO2e), or mineral wool (38 kgCO2e) (superhomes.org.uk). In these examples, however, more than twice the material is required to prevent the same amount of heat loss as PU, so the performance of these long lifetime materials with regards to their stability, flexibility, lifetime, handling and fitness for purpose must also be evaluated. When considering natural alternatives to PU, we also mustn’t forget to factor in the environmental and societal effects of these materials, like import costs, land and water intensive agricultural demand that competes with food crops, the need for fertilisers and pesticides, or the waste profile associated with such materials. When considering each of these points, the greening of PU production becomes a superior approach to offsetting its overall carbon and environmental footprint.
The historical production of PU and its precursors was heavily dependent on volatile organic compounds and petrochemical-based feedstocks, both of which are being addressed by new and existing companies worldwide. One of the biggest contributors to the use of petrochemical-based feedstocks in PU manufacture is the polyols inherent to its chemical structure. These polymers are most commonly polyether in nature and are prepared from the catalysed polymerisation of ethylene or propylene oxide. These epoxides are industrially synthesised from the carbon intensive oxidation or hydrochlorination of the corresponding alkene, which is collected as a by-product of oil refinement and which has an enormous carbon footprint. The potential replacement of some or all of this epoxide feedstock is clearly an effective approach to greening polyol production.
Increasing numbers of natural polyols based on plant oils or compounds are being developed industrially. Oil-based polyols can be prepared from a range of natural oils, such as castor, cashew, peanut or soy, with castor oil being one of the few natural products that does not require chemical modification. Alternatively, bio-based succinic acid polyols can be prepared from the fermentation of sugar. These polyols, in particular bio-based polyols, do offer advantages to downstream PU products over their wholly petrochemical-based counterparts in terms of increased abrasion resistance, tensile strength, thermal properties and hardness. As in the case of natural alternatives to PU however, these polyols also run into agricultural shortcomings, especially in competing with food crops for land use, as well as dependence on variable and uncontrollable factors like weather and seasons. As such, when processing and purifying the polyols, it can be difficult to produce constant quantities for downstream use. Furthermore, natural oil-based polyols require additional processing to remove odour, and typically must be blended with traditional petrochemical-based polyols to achieve comparable properties.
Using CO2 as a feedstock
An abundance of atmospheric CO2 presents another environmental issue that we currently face. It would therefore offer a win-win situation if petrochemical-based polyol feedstocks could utilise an otherwise waste material – for every tonne of epoxide replaced by CO2, three tonnes of CO2 would be avoided or utilised (Bardow, Green Chem.). Assuming 50% market adoption of such technologies, these numbers correspond to savings of ten million tonnes of CO2 a year, the equivalent to taking six million cars off the road or planting twelve million trees, that is, significant savings. Such polyols, known as polyethercarbonates, are the focus of a small, but increasing, number of companies. These new technologies differ in the amounts of CO2 that can be incorporated into polyols, but with a theoretical maximum of 50 mol%, significant environmental advantages are clearly possible. We at Econic have taken this approach one step further: our catalyst technologies allow for the bespoke incorporation of CO2 into polyols at industrially relevant temperatures and pressures, thereby allowing polyol producers to tailor their products for their downstream PU needs. What’s more is that the incorporation of CO2 also offers significant product advantages – the resultant rigid foams have improved flame retardance, whilst coatings, adhesives, sealants and elastomers show increases in their chemical, temperature and hydrolytic resistances. Economically, waste CO2 is expected to be at least an order of magnitude cheaper than its petrochemical-based counterparts. Irrefutable advantages are achievable in all aspects of the production of these green polyols, benefits which are in turn passed through to the PU industry and their consumers.
Moving towards responsible plastics
Frankly speaking, we cannot, and should not, remove plastics from our lives. The positive energy and application impacts that they impart simply cannot be reproduced by natural alternatives. Manufacturers and users alike can have a huge influence on reducing the ‘bad’ impact of plastics and shifting the balance towards ‘good’. We must urgently address how efficiently we use each plastic and move away from a ‘use and dispose’ mentality. Furthermore, plastics should be manufactured so as to not further perturb the state of our environment, but also to utilise the abundance of harmful waste products we have already created. As in the case of increasingly green PU, green and recyclable alternatives to many of the other plastics we rely on are being developed worldwide. The issue we now face is the wait for these new technologies to be adopted on a large scale by the industry, so that the plastics products so essential to our lives move towards being responsible materials.
To learn more about the endless potential that Econic’s catalyst technology can bring to greener plastics and waste CO2, please contact:
Richard French, Business Development Director on +44 1625 238 645
This blog was first posted by Plastic News Europe on 17/09/2018.