Co-processing technologies have reshaped the petrochemical landscape by allowing refiners to convert multiple feedstock types simultaneously within existing infrastructure. Rather than dedicating separate units to different raw materials, modern co-processing integrates streams such as waste plastics, biomass-derived oils, and conventional crude fractions into a single, flexible production train. This integration delivers significant operational advantages: it improves overall resource efficiency, reduces the carbon footprint of end products, and bolsters economic resilience against volatile feedstock markets. As regulatory pressure mounts and corporate sustainability goals tighten, the ability to co-process diverse inputs has moved from a niche capability to a core strategic priority for forward-looking petrochemical producers. The following sections detail the foundational concepts, recent breakthroughs, operational benefits, current challenges, and future trajectory of co-processing technology.

What Is Co-Processing?

Co-processing refers to the simultaneous treatment of two or more chemically distinct feedstocks in a single reaction or separation unit. In a petrochemical context, this typically means combining fossil-based hydrocarbons with renewable or recycled materials—such as pyrolysis oil from waste plastics, hydrotreated vegetable oil (HVO), or lignin-derived bio-oils—within a fluid catalytic cracker (FCC), hydrocracker, or hydrotreater. The fundamental principle is that the existing catalyst system and process conditions can accommodate a certain percentage of alternative feedstock without requiring a dedicated downstream unit.

Historical Context

The concept is not entirely new; refineries have long blended different crude grades or intermediate streams to meet product specifications. What distinguishes modern co-processing is the deliberate introduction of non-traditional feedstocks to achieve sustainability targets. Early trials in the 2000s demonstrated that up to 10 percent bio-oil could be co-processed in an FCC unit with minimal yield loss. Since then, advances in catalyst formulation and process control have pushed co-processing ratios higher, sometimes exceeding 30 percent for certain waste-derived streams.

Feedstock Categories

Three broad feedstock categories dominate current co-processing operations:

  • Biomass-derived oils: Includes vegetable oils, animal fats, and algae oils that have been hydrotreated to remove oxygen. These drop-in compatible intermediates can directly replace a portion of fossil gasoil or VGO.
  • Waste plastic pyrolysis oils: Produced by thermal cracking of post-consumer and post-industrial plastics, these oils contain a wide boiling range of hydrocarbons and require careful catalyst selection to handle contaminants such as chlorine and metals.
  • Lignin and cellulosic streams: Derived from woody biomass or agricultural residues, these oxygen-rich feedstocks pose challenges in deoxygenation and coke formation but offer the highest greenhouse gas reduction potential.

Recent Technological Advances

Multiple technology vectors have converged to make co-processing more reliable, efficient, and scalable. These range from fundamental catalyst chemistry to digital process control and novel reactor design.

Catalyst Development

Catalyst research has been the primary driver of co-processing progress. Traditional FCC catalysts, based on zeolite Y, were optimized for vacuum gasoil, not for oxygenated or chlorinated feeds. Researchers have now developed modified zeolites with tailored acidity, mesoporosity, and metal traps that tolerate higher levels of contaminants while maintaining activity and selectivity. Key innovations include:

  • Bifunctional catalysts that combine hydrodeoxygenation (HDO) and cracking functionality, enabling one-step conversion of bio-oils without a separate pretreatment stage.
  • Metal-doped zeolites that mitigate coke formation by promoting hydrogen transfer reactions, extending run length between regenerations.
  • Advanced binder formulations that enhance attrition resistance, a critical requirement when processing feedstocks containing abrasive particulates.

Recent pilot-scale studies from the Catalysis Research Group at Delft University show that a 15 percent loading of a lanthanum-promoted zeolite can achieve 92 percent conversion of a 70/30 blend of VGO and waste plastic oil, with gasoline yield exceeding 45 weight percent.

Process Optimization and Digital Control

Co-processing introduces compositional variability that fixed operating conditions cannot handle efficiently. Advanced process control (APC) systems, powered by machine learning algorithms, now continuously adjust temperature, pressure, catalyst circulation rate, and feed injection patterns to maintain optimal product slates despite feedstock fluctuations. These systems learn from historical data and real-time analysers, such as near-infrared (NIR) spectrometers that measure feed oxygen content and aromaticity every few seconds.

The IEA report on clean refining innovation highlights that digital twin technology has reduced yield variability in co-processing units by up to 40 percent while cutting energy consumption by 8–12 percent. Operators can simulate different feedstock blends offline, select the most profitable mix, and then implement it with confidence.

Integration of Renewable Feedstocks

While early co-processing focused on vegetable oils, recent efforts have expanded to include second- and third-generation feedstocks that do not compete with food production. Key developments include:

  • Hydrothermal liquefaction (HTL) of wet biomass: Produces a biocrude that can be co-processed in hydrocrackers at up to 25 percent blend ratios.
  • Catalytic fast pyrolysis (CFP) of lignocellulosic residues: Generates a low-oxygen bio-oil that requires minimal hydrotreating before FCC co-processing.
  • Chemical recycling of mixed waste plastics: Advanced sorting and dechlorination technologies now enable pyrolysis oils with chlorine content below 10 ppm, making them suitable for FCC feed without damaging downstream equipment.

Neste, a pioneer in renewable feedstocks, has demonstrated commercial-scale co-processing of waste plastic pyrolysis oil alongside renewable diesel feedstocks, achieving a carbon footprint reduction of 70 percent compared to fossil-only operations.

Environmental Control Technologies

Co-processing can alter emission profiles, particularly for sulfur oxides (SOx), nitrogen oxides (NOx), and particulate matter. Modern co-processing units incorporate several mitigation technologies:

  • Wet gas scrubbers that remove SOx and HCl with efficiencies exceeding 99 percent, critical when processing chlorinated plastic oils.
  • Selective catalytic reduction (SCR) units that cut NOx emissions by 90 percent through controlled ammonia injection.
  • Electrostatic precipitators and baghouse filters that capture catalyst fines and soot particles, ensuring stack opacity stays within regulatory limits.

These integrated environmental control systems allow co-processing units to operate under the same emissions permits as conventional units, avoiding the need for lengthy new source review processes.

Key Benefits of Advanced Co-Processing

The technological advances described above translate into tangible operational, environmental, and economic benefits for petrochemical producers.

Enhanced Efficiency and Yield

Modern catalysts and real-time process optimization directly improve product yields. Refiners report that co-processing a 10–20 percent blend of hydrotreated vegetable oil in an FCC unit can increase total gasoline and light olefin yields by 2–4 percentage points, thanks to the higher hydrogen content of the renewable component. At the same time, coke yield—a measure of inefficiency—often decreases because oxygenated bio-oils require less energy to crack than heavy VGO.

Environmental Sustainability

Lifecycle analysis consistently shows that co-processing renewable or waste feedstocks reduces greenhouse gas emissions compared to processing only fossil inputs. The magnitude of reduction depends on feedstock type, blend ratio, and the carbon intensity of the hydrogen used in hydrotreating. Typical lifecycle GHG reductions range from 40 percent for co-processed waste plastic oil to 80 percent for advanced bio-oils derived from forestry residues.

Furthermore, diverting waste plastics from landfills or incineration into co-processing creates a circular carbon economy. The ACS journal Energy & Fuels published a comprehensive review showing that co-processing 1 metric tonne of waste plastic in an FCC unit avoids 2.7 tonnes of CO₂-equivalent emissions compared to landfilling with energy recovery.

Resource Optimization and Circularity

Co-processing enables producers to use feedstocks that would otherwise be discarded or downcycled. Waste plastics, agricultural residues, and used cooking oil all gain a new life as high-value petrochemical building blocks. This resource optimization reduces dependence on virgin fossil feedstocks and buffers refiners against crude price volatility. It also aligns with the principles of industrial symbiosis, where one sector's waste becomes another sector's feedstock.

Economic Advantages

The economic case for co-processing rests on three pillars:

  • Feedstock cost advantage: Waste-derived feedstocks often carry a negative cost (gate fees) or are significantly cheaper than crude oil, improving gross margins.
  • Product differentiation: Co-processed products can be marketed as "renewable" or "circular," commanding premium prices in markets with low-carbon fuel standards (LCFS) or renewable energy certifications.
  • Capital efficiency: Co-processing avoids the need to build dedicated biorefineries or waste conversion units; instead, existing assets are leveraged with relatively modest retrofits, reducing capital intensity and project risk.

A recent techno-economic analysis by the International Energy Agency suggests that co-processing in existing refineries can achieve internal rates of return (IRR) of 15–25 percent at moderate blend ratios, outperforming standalone waste-to-fuels projects in many scenarios.

Challenges and Considerations

Despite the progress, co-processing is not without technical and operational hurdles that must be managed carefully.

Feedstock Variability and Contaminants

Waste-derived feedstocks exhibit inherent variability in composition, density, viscosity, and contaminant levels. Chlorine from PVC plastics, metals from packaging, and nitrogen compounds from proteins can poison catalysts, corrode equipment, and generate unwanted byproducts. Robust feedstock quality specifications, upstream pretreatment (such as dechlorination and filtration), and real-time blending controls are essential to maintain unit stability.

Catalyst Deactivation and Regeneration

Co-processing accelerates catalyst deactivation due to increased metal deposition, coke formation, and neutralization of acid sites by basic nitrogen compounds. More frequent catalyst replacement or regeneration cycles can raise operating costs. Advances in catalyst formulation—such as higher metal tolerance and easier regenerability—have mitigated this issue, but it remains a focus of ongoing research.

Product Quality and Certification

Co-processed products must meet the same specifications as their fossil-only counterparts. In some cases, blending bio-derived molecules alters the distribution of aromatics, olefins, or sulfur compounds, requiring downstream adjustments. Certification schemes, such as the International Sustainability and Carbon Certification (ISCC) ISCC PLUS system, demand rigorous mass balance accounting to attribute renewable content to specific products. Implementing the necessary tracking infrastructure can be complex and costly.

Regulatory and Market Uncertainty

Policy support for co-processed products varies by jurisdiction. While the European Union's Renewable Energy Directive (RED II) and California's Low Carbon Fuel Standard provide strong incentives, other markets lack clear mandates or carbon pricing. This uncertainty complicates investment decisions and may slow the deployment of co-processing capabilities in some regions.

Future Perspectives

Looking ahead, several emerging trends will shape the next generation of co-processing technologies.

Digitalization and Artificial Intelligence

The application of artificial intelligence in process control is still in its early stages, but early adopters report significant gains. Machine learning models that predict feedstock quality from spectroscopic data, optimize blend ratios for maximum profitability in real time, and anticipate catalyst deactivation patterns are becoming operational. These systems learn continuously, improving their recommendations as more data accumulate. The Internet of Things (IoT) and edge computing enable millisecond-level responses, ensuring that co-processing units operate at their thermodynamic and economic optimum even as feedstock quality drifts.

Novel Reactor Designs

While the FCC unit remains the workhorse of co-processing, new reactor concepts are emerging. Slurry-phase hydrocrackers that can handle heavy, solids-laden feedstocks are being tested for direct co-processing of biomass slurries and waste plastics without intermediate pyrolysis. Microchannel reactors, with their superior heat and mass transfer characteristics, offer the potential for highly selective co-processing at smaller scales, enabling distributed production hubs close to waste sources.

Expanding Feedstock Horizons

Research is actively exploring feedstocks beyond the current state of the art. Carbon dioxide captured from industrial sources, combined with green hydrogen, can be converted into synthetic hydrocarbons (e-fuels) that could be co-processed alongside fossil streams. Ocean-derived feedstocks, such as seaweed and algal biomass, offer high productivity without land use competition. And lignin—the most abundant renewable aromatic polymer—remains the holy grail for producing renewable BTX (benzene, toluene, xylene) via co-processing in FCC or hydrocracker units.

Integration with Carbon Capture and Storage

Co-processing units generate a concentrated CO₂ stream when processing oxygenated feedstocks (the oxygen leaves as CO₂ during deoxygenation). This presents an opportunity for integration with carbon capture and storage (CCS) infrastructure, potentially enabling carbon-negative operations if the feedstock itself is biogenic. Several projects in northern Europe are exploring this coupling, which could transform refineries from emission sources into carbon sinks.

Conclusion

Advances in co-processing technologies have transformed the petrochemical production landscape, enabling the simultaneous conversion of fossil, renewable, and waste feedstocks within existing refinery infrastructure. Catalyst innovations, digital process control, and robust environmental systems have addressed many of the early technical barriers, while favourable economics and policy incentives drive commercial adoption. Challenges remain—particularly around feedstock variability, catalyst longevity, and regulatory clarity—but the trajectory is clear: co-processing will become an increasingly mainstream strategy for producers seeking to enhance efficiency, reduce environmental impact, and build resilience in a rapidly evolving energy market. Continued investment in R&D, coupled with supportive policies and cross-industry collaboration, will accelerate the path toward a truly circular and low-carbon petrochemical sector.