Interplas Conference Preview: Polymers recycling: using the past to build now a better future
Ahead of her presentation at Interplas, Sibele Cestari, Enterprise Fellowship Researcher at Queen's University Belfast explains when seen under different perspectives transforming plastic waste into building materials presents many advantages.
The paradox of an economy requiring infinite growth on a finite planet urges remedial actions towards the environmental issue. Efforts focus on the search for sustainable global solutions, the pursuit of a Circular Economy (CE), optimisation of the life cycle of industrialised products, proper disposal of urban solid waste and reducing/rationalising the consumption of natural resources.
The CE assumes that producing a given recycled material will necessarily displace the production of its primary material one-to-one (meaning that every tonne of recycled material will replace a tonne of primary material). But as Roland Geyer pointed out in 2016, "There is no engineering relationship or law of physics that requires primary production to decrease as recycling increases". He suggests that studying the market's dynamics of demand and supply is "the only way to estimate displacement".
Most people believe that plastic is a single material, similar to traditional ones. But they are not. Plastic is one of the two types of polymers: plastics and elastomers (or rubbers). And plastics are subdivided into thermoplastics and thermosets, both having very different characteristics and recycling methods. Therefore, no universal solution will tackle the plastics problem. Although they represent only 0.4% of the global consumed materials and 0.7% of the UK's waste generation, plastic is the main target of environmentalists, waste managers and CE discussions.
Material Use
Source: Anna DeArmitt from Annalytix, after "Materials and the Environment: Eco-Informed Material Choice, Michael F. Ashby, Butterworth-Heinemann/ Elsevier, Oxford, page 18, UK 2009."
Waste generation by waste material, United Kingdom, 2016
Source: Kokel, Nicolas. n.d. 'The Great Plastic Crisis | LinkedIn'. https://www.linkedin.com/pulse/great-plastic-crisis-nicolas-kokel/. Accessed 28 July 2021.
Despite the disproportional concern with plastic waste, it is indisputable that industrialised polymers must not be in the environment. Waste polymers can – and should - be used as feedstock for new products, so that humanity would live more sustainably on a cleaner planet. The key is to treat post-consumer plastics scientifically, using the established knowledge about polymers science & technology and developing new techniques whenever necessary.
The United Nations Environmental Program (UNEP) showed in the 2012 "Greening the Supply Chain" Report that the construction industry alone consumes an impressive 40 to 50% of natural resources and around 43% of the energy produced on the planet. These numbers suggest that the sustainability of this sector must be addressed more efficiently, focusing on redirecting the amount of natural resources, water and energy consumed by commonly used building materials. Moreover, the transdisciplinary approach from industries other than that of Chemistry can bring new insights, adapt methods, create new tests, and give unexpected applications for materials taken for granted as useless waste.
Keeping in mind mainly the demand and supply dynamics, the idea of transforming plastic waste into building materials for low-income populations could be a suitable solution. The building industry - the second largest polymers market – offers a wide range of applications for recycled polymers and has considerably lower standards than the packaging industry. To achieve better mechanical properties, our team reinforced recycled plastic with other industrial waste materials like natural fibres (agricultural residues), demolition debris, and concrete waste. Some laboratory studies have already shown feasible pathways to recycle plastic waste into bricks, synthetic paper and alkyd resin.
The most exciting part of this concept is to literally remove plastic waste from the environment by systematically using it as raw material to build. Moreover, there is a reduction of the ecological footprint of the construction industry by developing a new range of building materials and products based on virgin polymers. They could replace traditional materials (like concrete and ceramic bricks, tiles, board paper and gypsum dry-walls) with more sustainable solutions that use recyclable synthetic polymers in substitution to finite natural resources.
When seen under different perspectives – environmental, economical and logical -, transforming plastic waste into building materials presents many advantages. The most important is time, an element that is usually forgotten when contemplating sustainable solutions. We generate 300 million tonnes of plastic waste because we didn't learn - yet - that plastic is never waste; it is always raw material. And all this waste won't degrade fast enough to prevent accumulation. Applying secondary recycling for plastics is faster than achieving its closed lifecycle. And removing these polymers from the environment as quickly as possible is more relevant to heal the environment than achieving unfeasible goals formulated on misconceptions.