Chemical Plastic Recycling is a process where by plastics can be disassembled into its component parts via chemical recycling techniques, which can then be converted into secondary raw materials of high value.
Additionally: Plastic waste streams that cannot be recycled mechanically due to technological, economic, or ecological reasons might be processed through chemical recycling.
Chemical recycling adds value to plastic trash that was previously unrecyclable by dissolving it into petrochemical feedstock that can then be recycled.
Any procedure that converts plastic polymers back into monomers (a molecule that can link to other identical molecules to form larger molecules) via chemical means recycling.
Plastic materials are frequently used in “chemical recycling” processes to generate a finite amount of energy once, destroying…
Plastic trash is broken down and recycled chemically to create new chemicals and plastics that function just like fresh materials.
The mission of Neste’s business is to promote the circular economy and combat climate change. In order to make it possible, we’re working on techniques to chemically recycle used plastic.
Recycling of plastics has historically been done mechanically. The non-mechanical recycling technologies that are presently being developed in the brand-new “chemical recycling” industry are summarised here.
Chemical recycling is a catch-all term for a variety of cutting-edge waste management technologies that make it possible to recycle plastics that are difficult or expensive to recycle mechanically.
Chemical recycling methods have the potential to significantly increase recycling rates and divert plastic waste from landfill or incineration by converting plastic trash back into base chemicals and chemical feedstocks.
Chemical recycling processes support mechanical recycling methods by allowing for the further value extraction of polymers after their economic viability for mechanical processing has been reached. In the case of hitherto difficult-to-recycle plastic items including films, multi-layered plastics, and laminated plastics, chemical recycling offers an option to landfilling and burning. The supply chain for plastics also receives virgin-quality raw materials through chemical recycling. This makes it possible to make food-grade polymers out of leftover consumer goods.
At the time of writing, several pilot plants demonstrating the viability of various chemical recycling processes were running. Commercial plants range in size from large, centrally located facilities with annual throughput capacities of 30 to 200 kt to considerably smaller, modular, distributed facilities with annual throughput capacities of 3 to 10 kt.
Chemical recycling (a subset of non-mechanical or advanced recycling) provides the ability to treat plastic waste that is challenging to recycle into high quality, high value recycled plastics, including waste generated from fossil and non-fossil sources.
Chemical recycling enhances mechanical recycling by preserving the circular nature of plastics and utilising waste that might otherwise have been difficult to recycle or unsuitable for some applications, such as food packaging or medicinal usage. A Mass Balance calculation and corresponding allocation must be done for chemically recycled materials[a].
What is Mass Balance Approach?
Inputs, outputs, and related information are transferred, tracked, and regulated as they pass through each stage of the relevant supply chain using the chain of custody concept known as mass balance.
To assess specific product features and verify the validity and transparency of related product claims, a chain-of-custody model must be selected, together with the associated rules and principles.
A mass balance model is one in which items or materials with a set of specified qualities are combined with products or materials lacking those characteristics in accordance with predetermined criteria, as shown below[b]:
Utilizing mass balance in the recycling of chemicals
The feedstock is assigned to a product where there is a market need for more circularity using a mass balance approach. The mass balance and certification approach enables the plastics industry to transform its goods using already-existing commercial assets.
What environments use mass balance?
Mass Balance is frequently utilised in certification programmes across numerous business industries.
Any technology that employs procedures or chemical substances that directly impact the chemistry of the polymers is referred to as chemical recycling.
Based on where the technologies’ outputs are located in the supply chain for plastics, they can be divided into three different categories (Figure 1). These groups include:
Chemical recycling is distinct from mechanical recycling, which employs procedures to clean up used polymers for reuse without appreciably altering the material’s chemical composition. The single-polymer stream is separated through mechanical recycling, washed, granulated, and then re-extruded to create recycled pellets suitable for moulding applications. The lengthy hydrocarbon chains in plastics are broken down into shorter hydrocarbon fractions or into monomers by chemical, thermal, or catalytic recycling techniques based on depolymerization and feedstock recycling. Contrarily, purification involves using solvents to remove additives from the polymers.
The major output created, a petrochemical feedstock, gives rise to the subgroup of chemical recycling known as “feedstock recycling.” The term “feedstock recycling” is used to distinguish thermal processes from chemical processes that purify the plastic waste stream (i.e., purification) or depolymerize the waste product into monomers (i.e., depolymerization) for further reprocessing or repolymerization. Thermal processes convert waste plastic into feedstock for a petrochemical plant.
A series of purification stages are then carried out to separate the polymer from additives and pollutants using the solvent-based purification method, which involves dissolving plastic in a suitable solvent (or solvents). The polymer(s) can be selectively crystallised after being dissolved in the solvent(s). A solvent may be used for selective dissolution if it can dissolve either the polymer of primary interest or every other polymer but the target one. The use of a selective solvent is essential for this. The precipitated polymer, which may be reformed into plastics and, ideally, is undamaged by the process, is the end product.
As it is a new technology, attempts are being made to scale it up to a level where it will be financially feasible. Waste plastics are typically collected as mixed polymers. The selective separation and recycling of waste components is thus the main obstacle.
The opposite of polymerization, depolymerization (also known as chemolysis), results in either single monomer molecules or shorter polymer pieces known as oligomers. Due to the fact that monomers and those used to make polymers are the same, depolymerized plastics have qualities that are comparable to those of virgin monomers. Chemical depolymerization’s main drawback is that technique can only be used on “condensation” polymers like PET and polyamides. The bulk of “addition” polymers, such as PP, PE, and PVC, which make up the majority of the plastic waste stream, cannot be used for their breakdown.
Several industrial facilities that degrade PET are now in operation, primarily using methanolysis and glycolysis processes. Although various projects are being developed for commercial uses in the upcoming years, hydrolytic processes are less established and are mostly used at laboratory and pilot-plant stages. Treatments based on aminolysis and ammonolysis are less well-established and advanced. The most often employed chemolysis techniques to stop the polymerization of urethane at the moment are glycolysis and hydrolysis. The primary method of chemically depolymerizing polyamides is hydrolysis.
Any thermal technique that breaks down polymers into smaller molecules to create the feedstock for petrochemical-style processing is referred to as feedstock recycling. Pyrolysis and gasification are the two primary processes in this context. Basic chemicals (such as hydrocarbons or syngas), which must be treated further to produce a polymer, are the outputs of feedstock recycling. The petrochemical sector can reuse materials more adaptably as a result.
By heating polymers without oxygen, or “cracking,” the pyrolysis process converts them into a variety of basic hydrocarbons (sometimes referred to as thermal cracking). The hydrocarbon vapour can subsequently be converted by a distillation process into a variety of goods, including heavy wax and oils, light oils, and gas. By changing the process time and temperature, it is possible to skew the production in favour of heavier or lighter materials. Additionally, heavier output products may be added again to the process for further cracking into lighter products.
In order to create the building blocks for polymers, pyrolysis products can be treated in a manner similar to how oil is. They can additionally be used straight as fuel.
Since polyethylene and polypropylene cannot be depolymerized directly into monomers, using pyrolysis to create feedstock for their synthesis could close a significant processing gap. Additionally, the plastic created would be of virgin-quality and could be applied in all the same ways (e.g., food packaging).
By utilising a suitable catalyst to encourage the cracking reaction, catalytic degradation can increase the production of pyrolysis. Temperature and duration of the reaction can be reduced in the presence of a catalyst. The procedure promotes the generation of lighter hydrocarbons and narrows the dispersion of carbon atom numbers in the final product. This increases the portion of the output product that can be used to create more plastics.
While single-polymer plastic trash can be recycled using pyrolysis-based technologies, these techniques are especially useful for handling contaminated and mixed-polymer waste streams.
In the past, pyrolysis has been used commercially for applications involving biomass, municipal solid waste, and charcoal. Pyrolysis of mixed plastics has been under development for the past 20 years in the waste industry, but it is only now becoming a commercial reality with a number of commercial plants already in operation and a large number of industrial-scale units anticipated to be put into service over the coming few years.
In the gasification process, a mixture of waste materials are burned to very high temperatures (between 1000 and 1500 °C) in the presence of little oxygen, which reduces the molecules to their most basic forms and produces syngas (a mix of hydrogen, carbon monoxide and some carbon dioxide). The syngas can then be used to make a number of chemicals (such as acetic acid, hydrocarbons, methanol, ammonia, and ammonia) for the manufacture of polymers, as well as fuel and fertiliser.
In order to obtain economies of scale, gasification is typically done in bigger process units. Such pyrolysis units often accept a mixed waste input stream, reducing the strain on the collecting and sorting system. Pre-treatment is frequently necessary for gasification to reduce moisture and boost calorific value. To address the needs for using syngas to chemical production, a very effective gas cleaning system at the high process temperature is required.
Syngas, a stream mostly composed of hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), and nitrogen, is created when waste plastics are gasified (N2). This gas can be utilised to create new hydrocarbons or be burned as fuel.
The practise of gasifying mixed garbage has been around for a while. Compared to pyrolysis facilities, gasification plants are normally constructed on a greater scale.
A chemical is broken down by water molecules in a close-to-critical reaction known as hydrolysis. In order to preserve the water in a liquid form, the temperature and pressure conditions for an HTT process are typically between 160 and 240 °C. Near-critical water has unique features that make it an effective medium for dissolving organic molecules, including high temperature and pressure. The hydrolysis, dehydration, decarboxylation, and depolymerization processes of HTT are crucial. Waste carbon fibre reinforced plastics (CFRP) and printed circuit boards (PCB) have been recycled via hydrothermal processing in a batch reactor. The inclusion of various additives and/or co-solvents has a significant impact on how well near-critical water can break down the resins and polymers in composite wastes. The separation of mixed waste (MW) into organic and inorganic components has been suggested as a potential application for hydrothermal treatment.
Technology is still in the development stage, and business activities are being planned.
Only 12% of the 260 million tonnes (Mt) of worldwide plastic waste, according to a McKinsey analysis, were recycled in 2016. According to the same report, by 2030, there would be 460Mt of plastic garbage, nearly doubling over the following ten years. Companies throughout the plastics value chain are already feeling the pressure from this anticipated expansion to take action on this issue. The research also envisions a situation in which, instead of the current global average of 12%, 50% of plastics may be recycled or repurposed by 2030. A large increase in collecting infrastructure and efficacy, increased sorting and mechanical recycling efficiency, and a successful rollout of chemical recycling infrastructure are all necessary to achieve this level of growth.
Mechanical recycling has so far proven successful in recycling PET, HDPE, and PP. By raising collection rates for these polymers and expanding to other polymers like LDPE, the demand for mechanical recycling capacity might be further stimulated. The McKinsey analysis claims that by 2030, global mechanical recycling rates might rise from 12% to 22% of the plastics waste market thanks to an increase in both collection and scope.
By processing polymer streams that mechanical recyclers are unable to manage, chemical recycling is expected to account for a portion of the rise predicted by McKinsey. Mixed-polymer waste streams and residual trash that has beyond the limits of mechanical processing may be treated using feedstock recycling techniques. These characteristics will be especially important for developing capacity in areas without the necessary infrastructure for collecting and sorting various types of plastic garbage.
In the high adoption scenario, it is estimated that $15 billion to $20 billion in infrastructure expenditure will be needed annually to reach the 50% recycling rate by 2030. This is in light of the petrochemical and plastics industry’s average annual investment over the previous ten years of $80 billion to $100 billion. By enabling up to one third of manufacturing to be made from recycled plastic within a decade and offsetting virgin oil and gas feedstocks, this new environment has the potential to drastically alter the dynamics of plastic production. According to this scenario, by 2030, the petrochemical and plastics industries’ development might be accounted for by two thirds of this new pool of recovered feedstocks.
Useful plastic materials are retained in use in a circular economy rather than being disposed of in landfills, burned, or released into the environment. The EU Circular Economy Package strategy calls for a binding landfill target to reduce landfill to no more than 10% of municipal waste by 2035, and the EU Circular Plastics Alliance has set a goal of using 10 million tonnes of recycled plastic in the production of new products annually in Europe by 2025. Investment in appropriate collection networks and recycling facilities will be necessary to create a circular economy and achieve these recycling and trash reduction targets.
By converting previously unrecyclable plastic trash into petrochemical feedstock, which can then be utilised as building blocks for fresh, virgin-quality polymers, chemical recycling adds value to previously unrecyclable plastic waste. Chemical recycling procedures serve as a link between the waste management and petrochemical industries and could act as a motivator for them to forge alliances in order to establish a circular value chain for plastics.
The circular economy is being embraced by a lot of petrochemical businesses. Borealis presented their plan to “establish plastic waste as just another common feedstock & as the new normal” for the chemical industry at the 2018 ICIS World Polyolefins Conference.
The petrochemical industry is working to increase the supply of plastics with recycled content and is committed to working with partners in the plastics value chain to research and develop the use of feedstocks from plastic waste in order to meet the rising sustainability demands of downstream market players, such as retailers, brands, and consumers.
Cross-industry alliances and business partnerships are emerging to develop the technological know-how and secure access to the waste plastics supply in order to achieve this coupling.
In 2017, Quality Circular Polymers (QCP), a premier mechanical plastics recycling business in the Netherlands, became a 50/50 partnership between LyondellBasell (a leading plastics, chemicals, and refining firm), and SUEZ (a worldwide resource management leader).
End of 2018 saw the first usage of pilot volumes of pyrolysis oil made from plastic trash provided by Remondis, a major European waste management company, as a feedstock in chemical giant BASF’s ChemCycling project. Customers from a variety of industries, including electronics and packaging film companies, participated in the pilot projects.