While the number of plastics regulations is proliferating globally, how to deal with the problem of plastic pollution is complex, particularly when viewed through the prism of climate change and carbon accounting.
Plastics sequester both carbon and energy. While the period of carbon sequestration is negligible when it comes to single-use plastics, some plastics, for example in the built environment, represent long-term carbon sequestration, often with significant energy conservation attributes.
The lowest-hanging fruit when it comes to emissions savings for heat and power is simply to use less. Three of the cheapest means of household energy savings are roof insulation, wall cavity insulation and UVPC double glazing. The most economical materials in all three areas are petrochemicals based.
Even for single-use plastics, there are emissions benefits. Plastic-wrapped foods reduce waste, which in effect reduces the oil intensity of food production because more produce is delivered for the same upstream inputs, for example fertilizer or the diesel used in agricultural machinery.
Plastic wrapping is also integral to the concept of ‘light weighting’. Light plastic packaging, which includes plastic bottles, has to be set against the increased weight of the alternatives, and the emissions created in their production and recycling. The replacement of plastic bottles with glass increases both product weight and size, which in turn raises transportation costs and emissions.
Moreover, some regulations, for example Kenya’s complete ban on plastic bags, is directed primarily at visible land pollution and the problems of choked waterways and livestock and wildlife ingesting plastic waste.
These problems first and foremost reflect inadequate waste disposal systems. If waste disposal was improved, the problem of what to do with the plastic waste would still remain, but the lack of adequate collection in many parts of the world is a key barrier to raising plastic recycling rates.
Burn or recycle?
There are essentially three options to deal with plastics – incineration, where the energy content is recovered, but the carbon content is released to the atmosphere, gasification, where the resultant syngas is reconstituted as fuel and then burnt, or recycling.
From a climate change perspective, there is little question that recycling appears the best option. From a practical perspective, incineration rates are likely to continue to rise, for example in dedicated waste-to-energy facilities, but also in the cement industry, which is always willing to take in cheap calorific feedstock for its kilns.
The emissions implications of incineration or gasification mean the policy focus is evolving around the concept of the ‘circular economy’, at the heart of which lies recycling. The focus also falls heavily on single-use plastics, which make up about 47% of the waste stream, but only 36% of primary plastics production. The aim is thus to implement regulation which improves the recycling rate.
However, even higher recycling rates do not necessarily spell doom for primary production of a commodity. Aluminium is one of the most recycled products in the world, with the recycling rate for all aluminium packaging reaching 51% in the UK in 2017 for example. Globally, however, there has been no real slowdown in the growth of primary aluminium production.
The current plastic recycling rate worldwide is estimated at about 14% of the plastic waste stream. If this increased to 30% by 2040, it would curb petrochemical demand for oil by somewhere in the region of 2.5 million b/d, but oil demand for petrochemicals would still rise significantly.
Moreover, the challenges posed by plastics recycling are much greater than for other products such as metal, glass or paper, and the more plastic that is recycled, the harder those challenges become.
Plastics production is made up of about 70% thermoplastics and polyurethanes, 16% PP&A fibers and 14% thermosets, adhesives, coatings and sealants. The latter two subsets are not recyclable using current technologies, and some, such as adhesives, sealants etc, are simply not collectable.
Even when it comes to thermoplastics and polyurethanes, some plastics are easier than others to recycle and the industry already processes the easiest source, which is industrial waste plastic. PET is the most commonly recycled plastic, but it is also used in PP&A fibers, so not all PET can be recycled. In addition, a plastic product may use more than one plastic, be combined with other non-plastic materials or simply, as with food containers, be contaminated. Separation or cleaning in theses cases raises costs.
Quantity and quality
Recycling rates also need to be approached with caution, as they are generally expressed as a percentage of plastics waste collected, which is significantly less than plastics products produced. An OECD study estimated that 14-18% of plastic waste generated is collected for recycling worldwide, which would mean somewhere in the region of 47-61 million tons a year.
Using the lower estimate, which is more consistent with other studies, and taking into account process losses for what are plastic products rather than virgin polymer and resin, and the OECD’s numbers would suggest about 34 million tons of recycled polymer and resin are re-entering the market, the equivalent of about 1 million b/d of displaced oil demand.
However, the complexities of plastic do not end there. The subset of plastic which can be recycled cannot be endlessly recycled. The majority of recycled plastic – about 80% -- is used to produce lower-grade materials rather than like-for-like replacements, and these lower grade products, for example fibres, do not then get recycled a second time.
Regulation will target the easiest to recycle plastics first – for example PET bottles – but the marginal cost of recycling will rise as the waste feedstock is broadened. This suggests that the global recycling rate will increase only very slowly, that the economics of plastic recycling will remain very challenging, and that the impact on oil demand for petrochemicals will be relatively slight.