Chemical Recycling – An Effective Tool For Plastic Waste Management

INTRODUCTION

The world is facing devastation caused by plastic waste.  Approximately 60% of 80,000 metric tonnes of plastic ever made is no longer in use by humankind and is instead either utilized as landfill or is released into the environment. If calculated on the basis of contribution per individual living on the planet, it amounts to about 400 kg¹. Once plastic materials are discarded into the environment, they end up in landfills or oceans because degrading them at ambient temperatures is difficult and they require decades to decompose. Hence, reduction, reuse and recycling are the three pillars of sustainable development that can help save the environment.

Traditional physical or mechanical recycling typically grinds down plastic into smaller components that are then mixed and molded to create low-grade plastic products. Even though the concept of chemical recycling of plastic waste has been known since decades, it has started to receive much attention only recently. Chemical recycling breaks down the plastic to molecular levels, thus facilitating the buildup of new materials based on the molecules that have the potential for a wide range of applications. The plastics are depolymerized to their respective monomers or oligomers. Several types of chemical treatment methods have been developed to deal with different types of commercial plastics^[1].

TYPES OF PLASTIC MATERIALS

Polyolefin based plastic materials, such as those based on linear density polyethylene (LDPE), high density polyethylene (HDPE), linear low-density polyethylene (LLDPE), polystyrene based, acrylate based-such as PMMA, polyurethane, and polyester are considered for chemical recycling.

TYPES OF METHODS FOR CHEMICAL RECYCLING

Various types of chemical recycling methods are available, based on the type of plastic waste material used. These include methods such as gasification, pyrolysis, solvolysis, supercritical fluid, depolymerization and microbial, wherein the plastic waste is broken down into monomers, the chemical building blocks, for the production of new plastic materials. However, problems exist with plastic materials such as single use plastics, multi-layer laminated plastics etc. which are difficult-to-recycle. This paper brings out the successful research efforts of select leading companies. 

RECENT DEVELOPMENTS

Plas-TCat chemical recycling technology from Anellotech uses a one-step zeolite catalyst-based process for the conversion of single-use plastics directly into basic chemicals, which are, in turn, used to make new plastics. The new process can be switched between two different production modes such as Hi-Olefins, which results in the production of olefins, or Hi-BTX, which produces mostly aromatics such as BTX and para-xylene.

Researchers working on the EU-funded ENZPLAST2 have developed a recycling technology that degrades the middle adhesive layers of multilayer materials. This facilitates   the easy recovery and recycling of other layers. This new technology is based on the isolation of microorganisms that are capable of biodegrading specific types of polymers. Biodegradation of plastics involves two steps:

• Binding of microorganisms to the polymer surface and
• Growing of the microorganisms using the polymer as a source of carbon.

This is followed by polymer degradation into CO₂ and water under aerobic conditions, and biogas and water under anaerobic conditions.

 (source)

Carbios, the polyethylene terephthalate (PET) recycling company based out of France, uses enzymes to depolymerize difficult-to-recycle multi-layered PET scrap. It has developed a biology-based solution that uses enzymes to break down widely used PET plastics and fibers. This approach gives new value to plastic, unlike the limited recycling potential of mechanical processes, thus preventing post-consumer plastics from manifesting as waste.

ReNew ELP has developed Cat-HTR™ (Catalytic Hydrothermal Reaction) process as a form of feedstock recycling, using water as the ‘agent of change’. The use of water plays a key role as it donates hydrogen during the cracking process and hence, no additional hydrogen is required. Also, the yield is high and the end products are stable. It is relatively insensitive to residual contamination, such as that from organic food matter and paper, thus eliminating the need for extensive pre-processing and segregation of the plastic feedstock. Cat-HTR™ can process all types of plastics, especially multi-layered materials such as composite films. The output can be tailored based on varying reactor operating conditions such as residence time and temperature.

INEOS Styrolution’s research project, ResolVe has shown that waste polystyrene can be chemically recycled to produce new products. The project investigated the effect of waste composition on the yield of styrene. A stable process is possible with a broad range of feedstocks, with the most suitable feedstock being lightweight packaging and expanded polystyrene. 

START-UPS

In recent years, a number of start-ups have started working on chemical recycling technologies. A few of them are presented below:

Obbotec’s Hydro-Pyrolysis is unique, as it recycles a mixed stream of bio and plastic into high quality oil. This is particularly advantageous in case of mixed waste streams that cannot be recycled due to difficulties in separation. A few such examples are contents of household garbage bins, restaurant bins, airplane bins, etc. or industrial applications such as the glasshouses where vegetables or fruits are grown alongside plastic sticks. Obbotec’s Selective Plastic Extraction (SPE) is an innovative chemical plastic recycling technology based on solvolysis. SPE can convert a mix of waste plastics into (near) ‘virgin’ granules because it removes all contamination from plastic, such as fragrances, dyes, coatings and plasticizers. Solvolysis is the only direct high quality ‘plastic-to-plastic’ solution that also deals with multi-layer plastics.

GreenMantra Technologies, a fast-growing tech start-up, produces value-added synthetic waxes, polymer additives, and other chemicals from recycled plastics. Additionally, building a production line featuring new technology, in collaboration with Sun Chemical, it will transform waste polystyrene into modified polymers for inks and other applications. Further, it is introducing its line of CERANOVUS polymer additives for enhanced asphalt performance in road applications.

Encina has plans to use its technology to crack hydrocarbons to create pyrolysis gasoline (pygas) that contains BTX aromatic hydrocarbons, which will be further extracted. 

INVESTMENTS AND COLLABORATIONS

There has been a significant number of collaborations in this area. Various organizations are funding this technology, which implies technology commercialization.

Japanese electrical engineering company Yokogawa Electric has signed an investment and partnership agreement with Jeplan, a polyester-material recycling company with an innovative chemical recycling technology. According to Yokogawa, the polyester resin produced using Jeplan’s BRING Technology has a quality equal to the conventional petroleum-based polyester resin.

Neste Oyj, an oil refining and marketing company located in Finland, and Mirova, a key player in sustainable finance, combinedly invested EUR 10 million in Recycling Technologies, a British plastic recycling technology provider for the acceleration and development of chemical recycling. Neste has also partnered with companies such as Ravago and Remondis, and has set a target to reach an annual capacity for processing over two thousand tonnes of waste plastic. It has a partnership with ReNew ELP and Australian technology developer Licella on a project to use mixed waste plastics as a raw material for fuels, chemicals, and new plastics.

Norwegian firm Grønt Punkt Norge has partnered with plastic-to-fuel specialist Quantafuel. Grønt Punkt Norge will supply up to ten thousand tonnes of post-consumer plastic packaging to Quantafuel’s new facility in Skive, Denmark, and the new plastic developed using chemical recycling is being supplied to BASF. Norwegian recycling company GemiNor is also participating in the project for developing a sorting line that is specifically tailored for Quantafuel’s needs.

Licella and Australian partner iQ Renew, with the support of BioLogiQ, will commercialize the ReNew ELP’s Cat-HTR technology in Australia, while global partner Mura Technology will be working alongside BioLogiQ to bring the Cat-HTR solution to China. ReNew ELP has won a £4.4m grant from Innovate UK to build a world-first plastic recycling plant at Wilton.

Toyo Styrene has licensed Agilyx Chemical Recycling Technology for a waste Polystyrene facility in Japan. The depolymerization plant will have a processing capacity of up to ten tonnes per day of post-use polystyrene. Toyo Styrene in turn will purify the styrene monomer oil produced from the technology into a highly purified styrene monomer using their proprietary purification technology.  The manufacture of styrene through depolymerization of post-use polystyrene has a lower carbon footprint as compared to virgin styrene monomer. This facility is expected to commence operations in early 2022.

Muroran Institute of Technology and Sumitomo Chemical Co. will accelerate joint research on a new chemical recycling technology, which chemically decomposes waste plastics and reuses them as raw materials for petrochemical products, including plastics. In another joint recycling project, Sumitomo Chemical is collaborating with Sekisui Chemical on a project that will process waste materials into polyolefins.

R Plus Japan Ltd. has invested in Anellotech Inc. to develop its innovative Plas-TCat technology for recycling difficult-to-recycle plastics. Plas-TCat chemical recycling technology uses a one-step catalytic process to convert single-use plastics directly into BTX, ethylene and propylene, which can be used in the manufacture of new plastics.

Braven Environmental, a leader in deriving fuel from landfill-bound plastic, will invest $31.7 million to establish a manufacturing operation in Virginia. Braven Environmental uses the science of pyrolysis, to break down waste plastics with minimal emissions. The output can be used to create new plastics or as fuel, produced with much lower carbon emissions than traditional oil or gas.

Carbios has entered into an exclusive partnership with Novozymes for producing its proprietary enzyme for complete recycling of PET-plastics and fibers. The agreement allows the production of Carbios’ proprietary PET-degrading enzymes at both, a demonstration level and an industrial scale, and also represents a critical step for Carbios in demonstrating the positive environmental impact of its technology, which ensures that it can provide a sustainable solution for the infinite recycling of PET-based products, such as water and soda bottles, plastic packaging and textiles. Large companies such as L’Oréal, Nestlé Waters, PepsiCo and Suntory Beverage & Food Europe have partnered with Carbios.

GreenMantra and INEOS Styrolution have signed a joint development agreement, which will align GreenMantra’s patented technology and INEOS Styrolution’s manufacturing infrastructure to convert waste polystyrene into chemical monomer building blocks that further promote the polystyrene circular economy by replacing a portion of virgin monomer feed in INEOS Styrolution’s polymerization process. This partnership will help in expediting the diversion of polystyrene waste from landfills by converting it back into valuable monomers. INEOS Styrolution and AmSty announced plans to construct a joint 100 tonne/d facility in Channahon that will function on the basis of the Agilyx advanced recycling technology to recycle used polystyrene products back into virgin-equivalent styrene monomer.  

RECENT PATENT PUBLICATIONS

Carbios has disclosed, in application WO2019122308A1, novel proteases having improved activity in degrading polyester containing material, such as plastic products. The proteases are particularly suited to degrade polylactic acid containing material. Also, the method is useful for increasing hydrophilicity of a polyester material and this may have particular interest in textiles production, electronics and biomedical applications.

Greenmantra Recycling Technologies Ltd. has filed two applications, WO2020118453A1, WO19227233A1,   related to the use of styrenic polymers synthesized via depolymerization of polystyrene to produce foam materials and water-based and solvent based formulations such as latexes, ink, paint, adhesives etc.

A chemical recycling method to obtain an aromatic compound from phthalate plastics by thermally decomposing the same in the presence of a nickel catalyst comprising silica or alumina-supported nickel, has been patented by Ricoh Co. Ltd. (JP2018141140A)

US10508186B2 has been granted to The University of North Carolina at Chapel Hill for a process to chemically recycle PET by utilizing a microwave absorber to optimize glycolytic depolymerization of PET via microwave irradiation. The process is carried out by combining PET with ethylene glycol and a catalytic system comprising a catalyst and a microwave absorber, to produce a heterogeneous reaction mixture, which is then followed by heating the reaction mixture through microwave irradiation to a temperature sufficient to produce a bis(2-hydroxyethyl) terephthalate (BHET) monomer.

Siontech Co. Ltd., in collaboration with Kumoh National Institute of Technology, has received a patent, KR101888612B1, for a method for chemical recycling glycol-modified PET waste such as oligomers produced as a by-product during the glycol-modified polyethylene terephthalate production. The depolymerization is performed to form an intermediate, followed by transesterification and, the glycol-modified PET can be used as a raw material for an unsaturated polyester resin, polyol or polyurethane, and an ester-based adhesive.

Toppan Printing Co. Ltd. has filed a patent, JP2019171759A2, related to a laminate film for packaging, which is capable of chemically recycled. The packaging material satisfies the requirements such as gas barrier properties, hot water resistance, aroma retention, impact resistance, pressure resistance, piercing resistance and flexure resistance. 

CONCLUSION

Chemical recycling technologies are promising in tackling the menace of plastic waste efficiently and effectively, while contributing significantly to the reduction of carbon footprint. While chemical recycling would operate alongside traditional mechanical recycling, it is likely to face limitations such as requirement of pure feedstock, standard sorted or re-treated plastic waste, lack of complete information on environmental and health impacts etc. Also, it is surrounded by many uncertainties and therefore, policymakers should work towards developing a right policy framework to bring regulation in this sector to reap the benefits of these technologies.