Plastics : Chemical Recycling Technologies in the Plastics Industry

Chemical recycling is a set of processes that break down plastic waste into its basic chemical components (molecules or monomers which have the ability to join together in long chains to create plastic materials), which can then be used to make new plastic materials or other chemical products. Unlike mechanical recycling, which physically grinds and melts plastics, chemical recycling alters the chemical structure of the polymer chains, potentially allowing for infinite recycling without quality degradation.

Key Chemical Recycling Technologies:

Pyrolysis:

• Process: heating plastics to 400-600°C in the absence of oxygen
• Outputs: primarily produces liquid oil similar to petroleum, along with some gases and char
• Best suited for: polyolefins (PE, PP)

Real-world example: PureCycle Technologies uses a proprietary solvent-based process to recycle polypropylene into virgin-quality resin

Gasification:

• Process: partial oxidation at high temperatures (>700°C) with controlled amounts of oxygen or steam
• Outputs: Syngas (hydrogen and carbon monoxide mixture) that can be used for fuels or chemicals
• Best suited for: mixed plastic waste streams

Real-world example: Enerkem converts municipal solid waste including plastics into methanol and ethanol

Solvolysis/Dissolution:

• Process: using solvents to selectively dissolve target polymers, separating them from contaminants
• Outputs: purified polymers that can be reprocessed
• Best suited for: PS, PC, PA

Real-world example: Purecycle Technologies' process that removes colors, odors, and contaminants from polypropylene

PS (Polystyrene) is a rigid plastic available in solid or foam forms. It's commonly used in food packaging, disposable items, and insulation due to its clarity, rigidity, and light weight. While inexpensive, PS has limited recycling options and poor environmental degradation.
PC (Polycarbonate) is a premium engineering plastic known for exceptional impact resistance and clarity. it's used in eyewear, electronics, and security applications. PC offers excellent toughness and heat resistance but has faced concerns about potential BPA leaching.
PA (Polyamide) or nylon, is a strong, abrasion-resistant plastic with excellent durability and heat resistance. it's used in automotive parts, textiles, and mechanical components where strength and low friction are required.

Depolymerization:

• Process: Breaking polymers back into their original monomers through chemical reactions
• Outputs: Monomers identical to virgin materials
• Best suited for: Condensation polymers (PET, PU, PA)
• Real-world example: Loop Industries uses a catalyst-driven depolymerization to break down PET into DMT (Dimethyl Terephthalate) and and MEG (Monoethylene Glycol).

DMT which is one of the two main building blocks of PET plastic, it is a white crystalline substance provides the rigid, aromatic structure that gives PET its strength and stability MEG (Monoethylene Glycol) is the second essential monomer for PET production, it is clear, colorless liquid alcohol forms the flexible links between DMT molecules in the polymer chain. When PET undergoes depolymerization recycling, it separates back into pure DMT and MEG, which can create new, virgin-quality plastic.

Hydrocracking:

• Process: Using hydrogen under pressure and heat with catalysts to break carbon-carbon bonds
• Outputs: Shorter hydrocarbon chains used for fuels or chemical feedstocks
• Best suited for: Mixed plastic waste
• Real-world example: Plastic Energy converts end-of-life plastics into TACOIL, which serves as feedstock for new plastic production. This technology transforms end-of-life plastics, particularly mixed plastic waste that's difficult to recycle conventionally into a hydrocarbon feedstock similar to crude oil

Advantages Over Mechanical Recycling:

Contamination Tolerance:

• Can process mixed or contaminated plastic waste that mechanical recycling cannot handle
• Eliminates need for perfect sorting or extensive washing
• Removes additives, dyes, and other contaminants through the chemical process

Quality Retention:

• Produces materials chemically identical to virgin plastics
• Avoids the quality degradation that occurs with repeated mechanical recycling
• Enables true "circular economy" for plastics. Circular Economy is an economic system aimed at eliminating waste and continually reusing resources

Versatility in Feedstocks:

• Can process multilayer and composite materials
• Handles plastics that have reached their mechanical recycling limit
• Some technologies can even process non-recyclable plastics like thermosets

Current Challenges:

Economic Viability:

• High capital investment for facilities
• Energy-intensive processes with significant operating costs
• Competition with low-cost virgin plastic production from petroleum

Scale-Up Issues:

• Many technologies still transitioning from pilot to commercial scale
• Process optimization for different waste streams still evolving
• Supply chain development for consistent feedstock quality

Environmental Considerations:

• Energy intensity and associated carbon footprint
• Potential for hazardous byproducts in some processes
• Life cycle assessments still being developed to compare with other options

Future Outlook:

Technology Integration:

• Combining mechanical and chemical recycling in unified systems
• Integration with renewable energy to improve sustainability
• Development of modular systems for distributed processing

Market Development:

• Growing brand commitments to recycled content driving demand
• Policy support through extended producer responsibility and recycled content mandates
• Premium pricing for chemically recycled materials due to quality equivalence to virgin plastics

Technological Advances:

• More selective catalysts increasing efficiency and reducing energy requirements
• Process innovations lowering capital and operating costs
• Artificial intelligence optimizing process parameters for variable feedstocks

Chemical recycling represents a pivotal advancement for the plastics industry, potentially enabling the recycling of millions of tons of plastic waste that currently ends up in landfills, incinerators, or the environment. While still evolving, these technologies offer a promising pathway toward a truly circular plastics economy where materials retain their value indefinitely.