LIBS and Plastic Recycling

Plastics have become so pervasive in our lives that we seemingly cannot avoid them. They are in your takeaway coffee lid, the chocolate wrapping, and the yogurt cup. Inspired by the Plastic Free July initiative, which promotes the reduction of single-use plastics consumption, today we look at another way of lowering the negative impacts of plastics: recycling. We will also show how Laser Induced Breakdown Spectroscopy (LIBS) devices may facilitate plastic analysis.

“There is no such thing as ‘away’. When you throw something away, it must go somewhere.”

– Annie Leonard

According to the UN experts’ 2023 report on plastic pollution, we now produce 400 million tons of plastic waste every year, with this number predicted to triple by 2060. Traditional methods of non-biodegradable plastics disposal, which involve burying the waste or burning it, harm the environment.

85% of single-use plastics are stored in landfills or other locations. When landfills are unregulated, the leaking of harmful substances that plastics contain, such as lead or mercury, may contaminate underground water sources and fertile soil. Plastic packages also decompose into small particles that enter the water we drink, and the living organisms we eat. Moreover, landfills risk running out of the space available, resulting in people dumping the waste in nature or in the ocean.

Incineration solves the space problem but further contributes to damaging the ecosystem. Burning plastics releases harmful substances, such as halogens, mercury, polychlorinated biphenyls, and dioxins. For instance, PVC incineration releases carcinogenic vinyl chloride. Hence, incineration endangers human and animal health. Plastic burning also contributes to climate change due to black carbon emissions. Neither incineration nor landfill storage are, thus, viable options for environment-conscious plastic waste disposal.

Since not all of the high-demand plastics are environmentally conscious yet, there is a pressing urge for plastic waste management methods that are more ecological. Recycling has been presented as one of such methods.

Benefits of plastic recycling

Unlike previously described plastic waste reduction methods, recycling enables the reutilization of polymers while curbing energy consumption and CO₂ emissions. Collecting previously used plastics to reprocess them into a new product contributes to achieving a circular economy.

Compared to discarding waste in landfills, recycling reduces soil contamination. Unlike incineration, recycling eliminates the necessity for extracting and utilizing fossil fuels to produce new plastic, thus lowering energy consumption.

Plastic recycling involves five general stages. After collecting the used plastic, it is sorted, washed, and shredded into smaller pieces. The final step is compounding, the creation of a new plastic product out of the old material.

To help with plastics disposal and to make recycling easier, the Society of the Plastics Industry has classified plastics into seven categories according to their resin type: PET, HDPE, PVC, LDPE, PP, PS, and OTHERS.

LIBS devices in recycling

LIBS is the only solution for in-line and on-line chemical analysis for the speed of industry standards. Studies show that a LIBS device can help with the sorting and identification of plastics thanks to its speed, preciseness, and its ability to detect even light elements.

Even though LIBS is the young sibling in the family of spectroscopy techniques, several studies have already examined its application in the analysis of plastics. LIBS devices have successfully analyzed toys, food containers, electronic waste, and other kinds of plastic products to detect toxic elements of Br, Cd, Cr, Hg, Pb, and Sb. With the urgent demand for efficient processing of plastic waste, studies have been conducted to demonstrate the successful use of LIBS devices also in particular stages of plastic recycling.

LIBS devices could assist during plastic sorting. Research has shown that LIBS machines are able to distinguish plastics from natural materials. They are also able to differentiate between the seven polymer types mentioned above as each type has a different C/H spectral line intensity ratio. This ability would enable fast plastic identification that may be performed either in a laboratory or on-site.

Two pivotal requirements for the devices employed in the stage of plastic sorting are speed and sensitivity to various elements. LIBS machines offer a fast inspection of the sample to provide the user with immediate analysis results displayed on the screen. Using LIBS technology also requires little to no sample preparation, and the user may conduct the analysis in the lab or on-site. Moreover, our own LIBS devices successfully detect and analyze even light elements that also appear in plastics, such as hydrogen.

In addition, LIBS machines enable better control of quality in the recycling process as they can determine the homogeneity of the sample. They check the purity of the recycled products to meet the required standards for the desired application. Previous studies have proven that LIBS devices are able to detect contaminants, such as metals. This prevents a compromised sample from entering another reprocessing stage.

Problems with plastic recycling

Plastic recycling is not a flawless method of eliminating the impact of plastics on the environment, however. Since plastic products contain carcinogenic chemicals affecting human and animal health as well as the environment, their recycling further perpetuates their toxicity. In addition, not all types of plastics are recyclable. In fact, only around 10% of all plastics produced have also been recycled so far.

Measures have been proposed to solve this issue. In 2021, the European Parliament presented tighter recycling regulations. A year later, it approved rules to decrease the amount of hazardous chemicals in waste and production processes to make plastic recycling safer and more efficient.

Although it helps reduce the amount of already existing waste, recycling alone will not fix the negative effects of plastic pollution. Initiatives like the elimination of plastic manufacture must also be taken to prevent further plastic pollution.

How can AtomTrace LIBS machines help with plastic analysis?

Our LIBS instruments already successfully assist in the analysis of plastic materials. Sci-Trace analyzed the concentration of Al and Mg in four samples of elastomers, with C being the matrix element. It also offered the chemical map of the distributions of these elements throughout the samples.