Mixed or Contaminated Waste Plastic Recycling through Microwave - Assisted Pyrolysis

A single type of thermoplastic polymer is easily recycled through a mechanical process, but this way can’t be followed in the presence of mixed or contaminated plastic. In this case, one of the main followed solutions is a thermochemical process and among them, microwave-assisted pyrolysis is one of the emerging technologies. This chapter offers an update of the microwave-assisted pyrolysis of mixed or contaminated waste plastic as a very promising example of chemical recycling. Furthermore, some unpublished results in this field will be reported such as the pyrolysis of waste lead containing polyethylene coming from end cycle batteries or the pyrolysis of waste polypropylene from facemasks used for covid protection. Finally, some examples of pilot plants will be described and commented as well as several industrial cooperations.

China’s ban of imported recyclable waste and its impact on the waste plastic recycling industry in China and Taiwan

In 2017 the Chinese government announced to a ban on the importation of several kinds of recyclable waste that could be replaced by domestic recyclable waste. Current research on this subject has placed an emphasis on the issues faced by exporting countries and Southeast Asia as an alternative destination of plastic wastes. However, there has been little study on changes in the waste recycling industry in China and other export destinations such as Taiwan. In this study, I conducted a field survey in China and Taiwan and reviewed the history of Chinese recyclable waste import policy and its impacts on plastic recycling industries. The results show that China switched from directly importing waste plastics from exporting countries to importing recycled pellets via third-party countries, primarily from Southeast Asia. Although Taiwan’s import volume of waste plastics has increased since 2018, improper (i.e. illegal) imports such as those commonly reported in Southeast Asian countries have not been reported in Taiwan. Even after Taiwan implemented tightened import controls in October 2018, it was still able to import enough recycled waste to meet domestic demand. The case of Taiwan shows that proper import controls can contribute to a more sustainable global circular economy.

Chemical upcycling of polymers

As the production volume of polymers increases, so does the amount of plastic waste. Plastic recycling is one of the concepts to address in this issue. Unfortunately, only a small fraction of plastic waste is recycled. Even with the development of polymers for closed loop recycling that can be in theory reprocessed infinitely the inherent dilemma is that because of collection, cleaning and separation processes the obtained materials simply are not cost competitive with virgin materials. Chemical upcycling, the conversion of polymers to higher valuable products, either polymeric or monomeric, could mitigate this issue. In the following article, we highlight recent examples in this young but fast-growing field. This article is part of the theme issue 'Bio-derived and bioinspired sustainable advanced materials for emerging technologies (part 2)'.

Rapid classification of plastics by laser-induced breakdown spectroscopy (LIBS) coupled with partial least squares discrimination analysis based on variable importance (VI-PLS-DA)

Combination of LIBS and VI-PLS-DA is a promising approach to achieve the online analysis and process control of waste plastic recycling.

Use of waste plastic aggregation in concrete as a constituent material

The amount of Plastics consumed annually has been growing increasingly in Bangladesh. Consequently, waste plastic recycling has become one of the major challenges in recent times. The present study has selected waste PET, a polymer compound of Polyethylene Terephthalate, to investigate its possible use as plastic aggregate in concrete application. The shredded waste plastic was used in concrete with partial replacement of 5%, 10% and 20% by volume of conventional coarse aggregate. Four types of concrete specimens including one without plastic aggregate, for comparison purpose, were prepared. All the concrete specimens were tested for its different mechanical properties after a curing period of 7, 21 and 28 days. Various physical properties of all aggregates and fresh concrete properties were also tested in the laboratory. The specific gravity of waste plastic aggregate was found 1.4 and the maximum density of concrete containing plastic aggregate was 115 lb/ft3. The density of concrete specimens containing plastic aggregate decreased with the addition of more amount of plastic aggregate. It was found that the concrete specimen containing waste PET at 10% volume showed higher compressive strength and higher modulus of elasticity than other specimens. The splitting tensile strength was about 8-11% of compressive strength. The flexural strength of concrete specimens containing plastic aggregate was lower than that of concrete without plastic aggregate. It was found that the strength of concrete containing PET aggregate falls in the category of lightweight concrete in terms of their strength, specific gravity and density. Thus, the waste PET aggregate could be effectively used to reduce the unit weight of concrete which results in a reduction in the dead weight of a structural concrete. Furthermore, it is concluded that the use of waste PET in concrete provides some advantages such as reduction in the use of conventional aggregate, disposal of wastes, prevention of environmental pollution, and energy saving.Progressive Agriculture 27 (3): 383-391, 2016

Recovery and Utilization of Waste Plastic Mulching Film in China Rural Areas – Tanking Awat County, Xinjiang as Example

The overuse of plastic mulching film in Awat county caused a gradual process of deterioration of the local soil environment, greatly polluted the environmental sanitation in rural areas and hindered the improvement of agricultural machinery's operation quality. After analyzing the related data of plastic mulching film use, and the status of its' recovery and utilization in Awat county, presented the optimizing countermeasures from the following aspects: strengthening the propaganda of the harmfulness of “white pollution”, promoting local peasants' ecological civilization consciousness; developing waste plastic recycling enterprises, broadening the recycling channels; formulating preferential policies to increase the support for waste plastic recycling; controlling and reducing the plastic mulching film residuals from farming techniques; intensifying residual plastic recycling by combining manual and mechanical recycling.