With a dizzying array of news about plastics lately, it’s hard to figure out what options are best for handling plastic waste. A large portion of the world does not recycle plastic waste, and countries that do are struggling to make the process cost-effective enough to make sense. Much debate exists about the best way to handle waste. Below are some of the options currently available, as well as technologies that are being developed.
Incineration/ Waste to Energy
What it is: Plastic (and other) waste is burned at high temperatures. Plastic is made from fossil fuels, which create a lot of heat when burned. In some instances, this heat is captured and used to heat buildings. In some facilities, the heat captured can power generators and create electricity. The negatives to this include large upfront costs to build the facilities, and the potential to emit pollutants, such as dioxins, acid gases and heavy metals into the atmosphere.
What it is: Melting plastic at very high temperatures (>700 degrees C) with a controlled, near-absence of Oxygen, creating a gas mixture called syngas (synthetic gas) that can be used to power turbines. The downside is that the process is a lot more expensive than natural gas, so the plants aren’t cost effective.
What it is: Plastics are shredded and melted, in a process similar to gasification, however because the plastic is shredded, lower temperatures and less oxygen is used. The result is the heat breaking plastic polymers down into smaller hydrocarbons, which can be refined and turned into diesel fuel. An advantage to pyrolysis is that the process works on films, pouches and multi-layer materials, which have been a challenge to typical recycling processes. The process is still relatively new, and not scaled up yet, so the costs are still higher than creating diesel fuel from fossil fuels.
What it is: The process of using enzymes to breakdown plastic is still in its infancy. In 2016, a group of Japanese researchers discovered a bacterium that grows on PET and partially feeds on it. The bacterium possesses two special enzymes: MHETase and PETase, which are able to digest PET plastic polymers. The use of these enzymes has not been scaled up to be effective enough to handle the amount of waste produced each year, but holds some promise for the future.
What it is: Plastics such as PET are considered polymers, or large molecules made of monomers, which are essentially like building blocks. In chemical recycling, polymers are broken down to their original monomer form, and these monomers can be re-polymerized and remade into new plastic materials. Chemical recycling offers a good alternative for materials that are typically hard to mechanically recycle, such as items that contain food residue.