Plastic is having a heyday at our planet's expense. A recent report by the Paris-based International Energy Agency (IEA) has revealed that demand for petrochemicals—plastics being one of the most significant—is accelerating faster than that for any other bulk material. Between 1971 and 2015, industrial plastic production volume grew by more than 10 times—more than cement (6.6), aluminum (4.9), or steel (2.9). This demand will even outstrip the original use of petroleum. “Petrochemicals will be the largest driver of global oil demand over the coming decades, ahead of cars, trucks, and planes,” the IEA states. “They will account for more than a third of the growth in oil demand to 2020 and nearly half the growth to 2050.”
Why is this grim news? Because petrochemicals are anticipated to add around 7 million barrels of oil consumed per diem by 2050. This consumption is equivalent to more than 3 million metric tons of carbon dioxide in daily emissions—more than 1 billion metric tons of carbon dioxide released annually—just for plastics and other chemicals derived from oil.
Today, petrochemical plastics are omnipresent in buildings. The construction sector, the second largest consumer of plastics behind packaging, accounts for 16 percent of plastic's total global consumption. Thermal insulation, carpet, piping, and window and door frames are now commonly made of plastic. But despite its functionality, versatility, and low cost, plastic plays an alarming role in exacerbating climate change and global pollution. Given these truths, architects should be compelled to rethink their use of the material.
One might instinctively recall the “three Rs”—reduce, reuse, and recycle. However, in the case of plastic, more nuance is required. To reduce consumption, for example, we should prioritize limiting the use of plastics that are difficult to recycle. According to a recent report in The Economist, a mere 13 percent of global municipal solid waste is recycled and only 10 percent of plastic is reclaimed. An added challenge for the U.S. is the recent ban on all imported plastic waste in China, which had previously accepted our nation’s garbage but has understandably ceased this practice due to environmental concerns. (China recycled the bulk of 7 million metric tons of imported plastic waste in 2016.) The good news is that this ban may stimulate the improvement of U.S. recycling efforts, a desperately needed change. Yet plastic’s relatively low production cost and high reclamation cost, as compared to paper or metals, present formidable challenges.
The rate of recycling varies significantly by polymer type, however, suggesting that if we must use petro-plastics rather than alternative materials, we should favor those with the most developed circular economies. A memorable rule-of-thumb is that the recyclability of commodity polymers closely parallels the recycle mark number, with one major exception. For example, the recycled proportion of type 1 plastic, polyethylene terephthalate (PET), in current supply is about 21 percent—making it the most recycled plastic, according to Materials and Environment (Elsevier, 2013). The fraction of recycled polyethylene (types 2 and 4) is 9 percent, followed by polypropylene (type 5) and polystyrene (type 6) at under 6 percent, and finally other plastics, including ABS, nylon, and polycarbonate (type 7) at under 5 percent. The sequential exception is polyvinyl chloride (Type 3), which constitutes only 2 percent of current supply in recycled form.
Unfortunately, PET is not commonly used in building construction, aside from electrical connectors and fittings; the polymer is mainly seen in consumer beverage containers and product packaging. However, other plastics are employed more frequently. Polystyrene (PS), for example, features prominently in building insulation products such as expanded polystyrene (EPS) and extruded polystyrene (XPS). As a thermoplastic, PS can be melted down and re-molded into new products up to 20 times without a loss of performance. Although EPS earned a bad reputation due to its high disposal rate and bulky volume, industry efforts have increased the recycling rate measurably in recent years. PS thus compares favorably with vinyl, which is recycled less frequently. However, PS management still has a long way to go before achieving a circular economy.
A better strategy is to forego virgin petro-polymers altogether, opting instead for recycled plastics that perform similarly. The initial approach could be to request recycled content in place of new when specifying polymer materials. Both EPS and XPS can be made using recycled resin. For example, Owens Corning manufactures XPS with a minimum of 20 percent recycled PS content.
Another strategy is to look for recycled plastic materials as surrogates for other traditional materials. Making roof tiles from recycled polymers, for instance, is a growing industry. Russia-based Altay Polimer-Krovlya, for one, combines melted waste plastic and sand to form resilient modular tiles designed to overlap like their ceramic counterparts. Similarly, manufacturers of products such as decking, siding, fences, and concrete additives have begun to embrace recycled polymers as key components.
If all architects adhered strictly to the above approaches when specifying materials, there would be a significant reduction in the demand for new petrochemicals. However, the ultimate objective should be to avoid using petro-plastics entirely—instead opting for bio-based polymers and other materials. Unfortunately, many biopolymers have their own challenges, such as their reliance on petrochemical-derived fertilizers and fuels.
These problems can be overcome, however, with an industry-wide transformation. Given the devastating effects that the current trend of accelerating petrochemical demand will have by 2050, we will have no other choice.
