Plastic production via advanced recycling lowers GHG emissions, study says

Plastic production through advanced recycling of used plastic can help displace higher carbon fossil-based production, reducing greenhouse gas (GHG) emissions and increasing the recycling rate, a new study shows.

The study, conducted by the U.S. Department of Energy’s Argonne National Laboratory and published in the November 2023 issue of Journal of Cleaner Production, is said to be the first to look at the full cycle of post-use plastic (PUP) from recycling to its integration in new plastic products at multiple facilities.

Specifically, the new plastics are low-density and high-density polyethylene (LDPE and HDPE, respectively). The recycling process used is pyrolysis, whereby plastics are heated to high temperatures in an oxygen-free environment. The main product is pyrolysis oil, a liquid mix of various compounds that can be an ingredient in new plastic. The oil can replace fossil ingredients like naphtha and gases to manufacture ethylene and propylene. They are two important monomers, or building blocks, for plastic production.

The study collected 2017-2021 operating data from eight companies with varying pyrolysis oil production processes. The analysis shows an 18% to 23% decrease in GHG emissions when making plastic with just 5% pyrolysis oil from PUP compared to crude oil-derived LDPE and HDPE, respectively.

When factoring in current end-of-life practices for many plastics in the U.S., such as incineration, there’s a further 40% to 50% reduction in GHG emissions when manufacturing pyrolysis-based LDPE and HDPE, respectively, according to the analysis. Reductions are much higher (up to 131%) in the European Union as more PUP is currently incinerated.

“As advanced recycling becomes increasingly efficient, it is poised to play a major role in achieving global sustainability goals by reducing waste and GHG emissions,” said Argonne Principal Energy Systems analyst Pahola Thathiana Benavides, a study author. ​“It can transform hard-to-recycle plastics into a multitude of high-value raw materials, reducing the need for fossil resources and potentially minimizing the environmental impact of waste management.”

In addition to GHG emissions, the Argonne team assessed the fossil energy, water consumption and solid waste impacts of converting PUP into new plastics. The most-likely scenario of 5% recycled materials when compared to virgin production shows a reduction of 65% to 70% in fossil energy use, a 48% to 55% reduction in water use and a 116% to 118% reduction in solid waste.

The study was supported by the American Chemistry Council.