Our recent post, Strategies for Recycling Polyethylene, explained some of the reasons why plastic recycling efforts could use some improvement. Plastics are petroleum-based products, which makes them inexpensive to produce but environmentally problematic. Our post discussed research to convert polyethylene back to petroleum. Other projects are focused on improving biodegradable plastic.
Biodegradable plastic sounds like a good idea but so far it hasn’t been a very successful one. Plastic pollution in the world’s oceans is a significant problem, to which so-called biodegradable plastics are a contributor. Jacqueline McGlade, chief scientist at the UN Environment Programme, told The Guardian that much of the biodegradable plastic floating in the ocean will only break down in temperatures of 50°C, much higher than ocean water temperatures. Furthermore, biodegradable plastics aren’t buoyant, so they won’t stay on the surface to be broken down by UV rays.
A phys.org article explains that the standard catalysts used to make biodegradable plastics are metal-based, which are difficult or expensive to remove from the final material, and do not degrade in the environment. However, researchers at Stanford and IBM Research have developed an alternative catalyst made from common organic compounds that can be produced at a lower cost with less environmental impact. The new catalyst can be used to generate several varieties of plastics suitable for different functions, including polylactic acid, a commercial compostable biodegradable polyester used to make disposable plastic tableware. It also has medical applications for resorbable sutures, stents, biomedical implants, and drug-delivery materials. Everyday items such as food packaging and non-woven fabrics are also a possibility. The study was published in Nature Chemistry.
The development of truly biodegradable plastic will be a welcome addition to current efforts to reduce plastic pollution. According to the ISRI fact sheet on plastic recycling, the technology to cost effectively sort and recycle plastic is only 25 years old, and recycling activities are hindered by outdated laws and regulations as well as the perception that recycled plastic is inferior to new.
Plastic must be properly identified, sorted, and cleaned before it can be recycled. Failing to do so can cause major equipment damage. The various plastic grades have different melting temperatures which can vary widely; feeding the wrong plastic grade into the extrusion furnace can result in furnace damage, production shut down, and significant operational losses. Furthermore, recycled plastic prices fluctuate, so misidentifying plastic can cause a recycling operation to lose money.
Separating different recyclable plastics from each other so that they are processed correctly requires complex chemical analysis. In addition to separating polyethylene items from other plastics, different types (densities) of polyethylene need to be separated, as do items co-polymerized with other types of plastics. Read Density and Copolymer Content in Polyethylene Samples by FT-NIR Spectroscopy to learn how Fourier transform near-infrared spectroscopy (FT-NIR) provides a means to identify and analyze various polyethylenes.
And please do not use the Burn n’ Sniff test.