Thermochemical Liquefaction
Quick Overview
Thermochemical liquefaction is a chemical recycling technology that converts solid plastic waste into liquid hydrocarbons (pyrolysis oil/LWP) through thermal decomposition, enabling circularity for hard-to-recycle plastics.
What Is Thermochemical Liquefaction?
Thermochemical liquefaction is a family of thermochemical conversion processes that transform solid plastic waste into liquid hydrocarbon products — primarily pyrolysis oil (also called liquefied waste plastic or LWP). It is a cornerstone technology for chemical recycling (also called advanced recycling), enabling the conversion of mixed, contaminated, and hard-to-recycle plastic streams back into virgin-quality feedstocks for new plastic production.
Unlike mechanical recycling, which physically melts and reprocesses plastics (requiring clean, sorted streams and suffering quality degradation), thermochemical liquefaction breaks polymer chains down to the molecular level — producing hydrocarbons that can be processed in existing petrochemical infrastructure (steam crackers, refineries) to make new plastics indistinguishable from virgin materials.
Types of Thermochemical Liquefaction
| Type | Temperature | Pressure | Key Characteristics | Best For |
|---|---|---|---|---|
| Pyrolysis | 300–500°C | Near atmospheric | Most mature for plastics; inert atmosphere; produces oil, gas, char | Mixed polyolefins (PE, PP, PS), films, contaminated streams |
| Hydrothermal Liquefaction (HTL) | 250–350°C | 5–20 MPa (supercritical water) | Processes wet feedstocks without drying; water acts as solvent/reactant | Wet biomass, mixed waste with moisture, some plastics |
| Solvent Liquefaction | 200–350°C | Moderate | Uses solvents to dissolve/depolymerize; lower energy potential | Specific polymers (PET, PU), selective depolymerization |
| Catalytic Pyrolysis | 300–450°C | Near atmospheric | Catalysts (zeolites, etc.) improve yield, selectivity, quality | Higher-value products, lighter fractions |
Direct Thermochemical Liquefaction (DTL) is an umbrella term covering pyrolysis and solvent liquefaction — technologies that directly convert solid feedstocks to liquids without gasification intermediate.
The Process: How It Works
Mixed Plastic Waste → Pre-processing (sorting, shredding, drying)
↓
Thermochemical Liquefaction Reactor
(Pyrolysis / HTL / Solvent-based)
↓
Pyrolysis Oil / Liquefied Waste Plastic (LWP)
+ Non-condensable Gas (fuel for process heat)
+ Char / Solids (inert fillers, carbon black)
↓
Upgrading / Hydroprocessing (refinery)
↓
Renewable Naphtha / Drop-in Feedstocks
↓
Steam Cracker → Monomers (Ethylene, Propylene)
↓
Polymerization → Virgin-Quality Plastics
Key Technical Parameters
| Parameter | Typical Range (Pyrolysis) |
|---|---|
| Reactor temperature | 400–500°C |
| Residence time | Seconds to minutes |
| Pressure | 1–5 bar (near atmospheric) |
| Atmosphere | Inert (N₂) or vacuum |
| Plastic-to-oil yield | 70–85% (polyolefins) |
| Gas yield | 10–20% (process fuel) |
| Char/solids | 5–15% |
| Feedstock moisture | <5% (pre-dried) |
Commercial Landscape
Alterra Energy (Akron, Ohio) — Proven at Scale
- Technology: Patented thermochemical liquefaction (pyrolysis-based DTL)
- Facility: 60 tons/day commercial showcase (operating 5+ years continuously)
- Output: ~300 barrels/day LWP
- Partnerships: Licensing to Freepoint Eco-Systems (Gulf Coast), Nerea™ with Technip Energies & Neste
Plastic Energy (UK/Spain/France/Netherlands)
- Technology: TAC™ (Thermal Anaerobic Conversion) pyrolysis
- Facilities: Multiple commercial plants in Europe
- Partners: TotalEnergies, SABIC, ExxonMobil, LyondellBasell
Agilyx (USA)
- Technology: Pyrolysis for polystyrene (depolymerization to styrene) and mixed plastics
- Facility: Tigard, Oregon + licensing globally
Brightmark (USA)
- Technology: Pyrolysis, Ashley, Indiana facility (100,000 tons/year target)
Freepoint Eco-Systems (USA)
- Technology: Licensing Alterra’s thermochemical liquefaction
- Project: Gulf Coast Advanced Plastics Recycling Facility (Houston area)
Feedstock Suitability
| Plastic Type | Pyrolysis | HTL | Solvent | Notes |
|---|---|---|---|---|
| PE (HDPE, LDPE) | ✅ Excellent | ✅ Good | ⚠️ Limited | Primary feedstock |
| PP | ✅ Excellent | ✅ Good | ⚠️ Limited | Primary feedstock |
| PS | ✅ Excellent | ✅ Good | ✅ Good | High monomer yield |
| PET | ⚠️ Challenging | ⚠️ Limited | ✅ Excellent | Better: methanolysis/glycolysis |
| PVC | ❌ Avoid (HCl corrosion) | ❌ Avoid | ❌ Avoid | Must be removed pre-process |
| Multilayer films | ✅ Good | ✅ Good | ⚠️ Limited | Key advantage vs. mechanical |
| Contaminated waste | ✅ Good | ✅ Good | ⚠️ Limited | Pre-treatment needed |
Upgrading: From Pyrolysis Oil to Circular Feedstock
Raw pyrolysis oil contains impurities (heteroatoms, olefins, metals) requiring upgrading/hydroprocessing in a refinery before steam cracker use:
- Hydrotreating — removes S, N, O, Cl; saturates olefins
- Distillation — separates naphtha, diesel, heavy fractions
- Naphtha fraction → steam cracker feedstock
- Mass balance allocation (ISCC PLUS) → certified circular polymers
Neste’s Porvoo facility (commissioned March 2026, €111M) is the world’s largest dedicated LWP upgrading unit, designed specifically for this hydroprocessing step.
Advantages & Challenges
Advantages
- ✅ Handles mixed, contaminated, multilayer plastics mechanical recycling cannot
- ✅ Produces virgin-quality feedstocks (drop-in for existing crackers)
- ✅ True circularity for polyolefins (PE, PP) — infinite recycling potential
- ✅ Complements mechanical recycling (takes the “reject” streams)
- ✅ Reduces fossil feedstock demand and plastic waste incineration/landfill
Challenges
- ⚠️ Energy intensive (high temperatures, though gas byproduct often fuels process)
- ⚠️ Feedstock pre-processing critical (PVC removal, drying, sizing)
- ⚠️ Upgrading required — raw oil not cracker-ready
- ⚠️ Economics — competes with cheap virgin naphtha; needs scale & policy support
- ⚠️ Yield losses — each cycle has ~15-30% mass loss to gas/char
Regulatory & Policy Context
- EU: Counts toward recycled content targets under PPWR (Packaging & Packaging Waste Regulation) if mass-balance certified
- US: State-level advanced recycling laws (20+ states) classify as manufacturing, not waste management
- Certification: ISCC PLUS mass balance is the dominant chain-of-custody standard
- LCA: Studies show 30-50% GHG reduction vs. virgin plastic (depends on energy source, displacement assumptions)
Related Glossary Terms
- Chemical Recycling — Broader category including depolymerization, gasification
- Pyrolysis Oil — Primary liquid product
- Liquefied Waste Plastic (LWP) — Synonym for upgraded pyrolysis oil feedstock
- Hydrothermal Liquefaction (HTL) — Water-based variant
- Pyrolysis — Most common thermochemical liquefaction type
- Steam Cracker — Downstream unit converting naphtha to monomers
- Mass Balance — Certification for circular content allocation
- Depolymerization — Polymer-to-monomer recycling (different mechanism)
- Alterra — Leading commercial operator
- Neste — Largest LWP upgrader
Last updated: July 3, 2026
Standards & Certifications
- ISCC PLUS (mass balance certification)
- ASTM D7566 (for upgraded SAF pathways)
- EN 13432 (not directly applicable - this is for compostability)
Major Producers
- Alterra Energy (patented DTL technology, Akron Ohio showcase)
- Plastic Energy (TAC™ pyrolysis technology)
- Agilyx (pyrolysis for polystyrene and mixed plastics)
- Brightmark (pyrolysis, Ashley Indiana facility)
- Freepoint Eco-Systems (licensing Alterra technology)
- Recycling Technologies (UK, RT7000 pyrolysis)
Key Applications
- Chemical recycling of mixed plastic waste
- Production of pyrolysis oil / liquefied waste plastic (LWP)
- Feedstock for steam crackers
- Circular plastics production