Waste-plastic processing provides global challenges and opportunities
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Energy Sector Analysis
Converting waste plastics back to monomers or to lower molecular weight oligomers—a process called depolymerization—offers the most significant return on investment.
Waste-plastic processing provides global challenges and opportunities By Thomas Degnan Feature Editor: Subhash L. Shinde
W
e are drowning in plastic waste. In 2015, 9.1 metric tonnes of plastic waste flowed into our oceans. Experts predict that by 2050, the total amount of plastic waste could amount to 850–950 metric tonnes. That will exceed the total mass of fish in the oceans. Ironically, unmanaged leaks of waste plastic into rivers and streams are only a small, though visible, part of a much more significant problem. Major US petrochemical companies have invested heavily in ethylene and propylene production over the past decade because of the huge recent production of shale gas and natural gas liquids. Domestic US production volumes of the two largest volume plastics, polyethylene (high-density and low-density) and polypropylene are projected to grow at a compound average rate of 4.6%. Globally, this growth rate is only slightly lower (4.0%). Similar growth rates are projected for polyester (6.0%) and polyvinylchloride (2.3%). These volumes of virgin plastic, much of which will be used in single-use packaging, will place more duress on what is already a strained waste-handling system. Only 13% of all plastic is currently recycled—12% by mechanical means and 1% by monomer recycling. The vast majority of plastic waste (40%) finds its way into landfills, while another 25% is incinerated. Some of the energy value of plastic waste is recovered as power via incineration. However, analyses of current incineration practices show that the efficiency of associated energy recovery through incineration is typically low. Only about 14–28% of the energy value of the incinerated plastic is recovered as electricity. In effect, incineration has led to increased carbon emissions without the concomitant energy generation. Up until last year, China handled approximately half of the world’s recyclable waste. This all changed with the implementation of China’s “National Sword” policy in January 2018. The new policy banned the import of most plastics and other materials that China had been accepting for more than a quarter of a century. China’s waste-plastic imports plunged by more than 99% in the past year, producing a major shift in how the world confronts its growing waste-plastic problem. The unsustainable nature of the current typical product life cycle of both durable and single-use plastics has not been lost on the global polymer industry. In January, approximately 30 companies banded together to establish the Alliance to End Plastic Waste (AEPW). The companies have committed to spend USD$1.5 billion during the next five years to create solutions to eradicate plastic waste in the environment. Federal research into waste management is funded primarily through the US Environmental Protection Agency, whose budget for waste reclamation and
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