Batch vs. Continuous Manufacturing

Is The Nanomaterials Industry Lagging or Leading?

In the world of manufacturing, two dominant paradigms vie for supremacy: batch and continuous processes. At first glance, continuous manufacturing presents itself as a modern-day marvel – a seamless and constant production method that, on paper, seems to promise efficiency, consistency, and reduced waste. And yet, in a surprising twist of industrial reality, a vast majority of industries remain anchored to batch processes – including the nanomaterials industry.

This poses a thought-provoking question: Is the persistent reliance on batch manufacturing indicative of industries being mired in outdated practices? Or do underlying practical challenges cast shadows over the premise of continuous manufacturing? This article delves into the intricate factors guiding this industrial choice, revealing a landscape far more nuanced than it might initially appear.

Historical Context: The Rise of Batch Manufacturing

To understand the staying power of batch processes, we must travel back in time. Batch manufacturing finds its roots in historical periods when resources were limited, and customization was the order of the day. Craftsmen worked on products in small groups, crafting and completing a batch before moving on to the next. This methodology provided flexibility. If there was a sudden change in market demand or an alteration required in design, it was relatively easy to adapt without wasting extensive resources.

As industries grew and became more specialized, the benefits of the assembly line became apparent. Batch processes evolved but didn’t vanish. It allowed companies to respond dynamically to market fluctuations, produce a diverse range of products, and maintain a handle on quality control. This flexibility and adaptability, often essential for industries like pharmaceuticals or specialty chemicals, made batch manufacturing a mainstay.

Future Dreams: The Allure of Continuous Manufacturing

Enter the continuous process. Imagined as the epitome of efficiency, this method involves non-stop production. Raw materials are continuously fed at one end, with finished products emerging at the other. Theoretically, this minimizes downtime, maximizes product output, and provides consistent product quality. Industries with significant scale, like oil refining or certain food production lines, find this method invaluable.

But, continuous manufacturing, with its seamless production and enhanced efficiency, is not without its limitations and challenges. Interestingly, there are striking similarities between its implementation in the nanomaterials industry and the pharmaceutical industry.

Nanomaterial Manufacturing & Its Parallels to Pharmaceuticals

Manufacturing nanomaterials and pharmaceutical drugs, though tailored for different end-products, have remarkable parallels in their production methodologies.

While their price points are widely divergent, at the heart of both is a demand for absolute precision and control. Minor shifts in composition or structure can drastically alter the functionality or efficacy of the resulting product. This underscores the importance of unwavering attention to detail in every production phase. Equally crucial is the commitment to rigorous quality standards. This is a pledge to drug safety and effectiveness for pharmaceuticals, while nanomaterials focus on attaining specific material properties.

And yet, as of 2022, thirteen (13) pharmaceutical drugs are made by continuous manufacturing,¹ a mere 0.03% of the over 19,000 prescription drugs approved in the US market.² The statistics are similar across Europe and Japan.¹

With all the talk about continuous manufacturing, why are most nanomaterials and pharmaceuticals, made through batch processes? As a recent example, Pfizer transitioned its Lipitor drug to a continuous process, however, the company’s experience was unsatisfactory. Famously, Pfizer’s CEO later said that to realize the full benefits from investments in continuous manufacturing, high-volume production was needed.³

Continuous Manufacturing: The Domain of High-Volume Basic Chemicals

When we disentangle the layers of continuous manufacturing’s applicability, it becomes evident that its most profound utility emerges in high-tonnage, single-product scenarios. This is no more evident than in commodity chemicals familiar to the general population such as:

Ammonia (NH₃): A key component in the production of fertilizers, nitric acid, and other chemicals
Chlorine (Cl₂): Employed in producing PVC, disinfectants, and various other chemicals
Polyethylene (PE): The most common plastic, used in packaging, bottles, toys, and more
Polyvinyl Chloride (PVC): Used in producing pipes, cable insulation, and other products
Polystyrene (PS): Used in the production of packaging, insulation, and disposable items

Continuous manufacturing’s essence lies in the unbroken flow of raw materials through meticulously designed units that consistently produce a finished product. From an engineering standpoint, this is a marvel of design and efficiency. Economically, it represents an approach that demands high initial investment but promises reduced marginal costs over an extended timeframe.

To provide a sense of scale, 157 million metric tons of polyethylene⁴ and 182 million metric tons of ammonia⁵ are produced annually. Even in more “niche” commodity chemicals, such as titanium dioxide, about 4 million metric tons⁶ are produced annually. These are manufacturing plants that have break-even points, where total revenue equals all costs, of around 60% of plant capacity. Suitable investment returns are typically achieved when a plant is running at or over 80% of capacity.

Where Continuous Manufacturing Shines

The investment and technical intricacies of establishing a continuous process necessitate an environment where the process can run undisturbed for prolonged periods. Here’s why:

Economies of Scale: The primary advantage of continuous manufacturing is economies of scale. Often these economies of scale are not driven by improvements in raw material costs but decreased labor and energy usage. By their very nature, the method demands a high capital expenditure for the design, engineering, installation, shake-down and accreditation of specialized equipment. The return on this investment is maximized only when the plant operates at a high capacity, justifying the high initial outlay.

Steady-State Operations: Once a continuous process reaches its steady state, it can run optimally with minimal disturbances. However, reaching this state requires time and often consumes a lot of raw material. Thus, short operating times undercut the benefits of continuous processes. In a massive tonnage setting where the plant operates continuously, these startup inefficiencies are diminished over the long run.

Energy Efficiency: Continuous processes can sometimes exhibit better energy efficiency than their batch counterparts due to consistent operating conditions. This is especially the case where there would otherwise be high temperatures ramp-up and ramp-down in a comparable batch process. This factor becomes significant in industries where plants run 24/7, leading to substantial energy savings.

Process Control and Consistency: A continuous plant offers consistent product quality due to the homogeneity of the process conditions. In scenarios where an industry produces only one product, this becomes crucial, as there’s no room for variation in product specifications.

Constraints of Continuous Manufacturing

Continuous manufacturing, despite its merits, has its challenges, especially when viewed through the lens of diverse product lines:

Adaptability Issues: Engineering a continuous plant is a precise endeavor tailored to a specific product. Altering this for another product can be capital and time-intensive, if it’s technically possible. Economically, this diminishes returns and challenges the feasibility of diversifying products in such setups.

Economic Risks of Downtime: Every hour a continuous process isn’t running is a significant economic loss. Engineering solutions can minimize downtimes, but the economic implications of operational disruptions are far more pronounced in continuous processes than batch processes.

Batch Manufacturing: A Dominant Force in Specialty and Fine Chemicals

In the broad world of chemical manufacturing, the transition from base chemicals to fine and specialty chemicals presents unique challenges and requirements. Base chemicals, often produced in massive quantities, are the building blocks, while fine and specialty chemicals are tailored for specific applications and hence demand a nuanced approach to production. Nanomaterials, a smaller subset of specialty chemicals, fall into this category.

As industries dive deeper into the realm of specialty chemicals, they encounter a staggering array of nearly 300,000 compounds,⁷ each with their unique properties, applications, and production needs. This complexity is further underscored by statistics from the European Union. According to their data, a significant 86% of chemical compounds are produced in volumes of 10,000 metric tons or less per year, with 74% less than 1,000 metric tons per year.⁸ Such limited volumes, combined with the specialized nature of these materials, make continuous processing less viable. Instead, the production of these myriad compounds, with very few exceptions, falls squarely into the realm of batch processing. By most estimates, 85% of manufacturing in the specialty and fine chemicals market is done via batch processing. But why?

The very nature of these chemicals and the markets they cater to make batch processing an optimal choice. Here are the main reasons why specialty chemicals are predominantly manufactured using batch processing:

Variability and Complexity: Specialty chemicals often require intricate and multifaceted synthesis processes, which might involve many different steps with dissimilar takt times and processing conditions. Batch processing allows for this level of variability, enabling manufacturers to adjust for each stage of the process.

Volume Considerations: Unlike bulk chemicals, which are produced in enormous quantities, specialty chemicals are usually produced in “smaller” volumes tailored to specific market demands. Batch processing is better suited for such smaller, precise volumes, allowing for efficient production without the need for continuous operation.

Flexibility: The specialty chemicals market can be dynamic, with fluctuating demands or the emergence of new application areas. Batch processing provides the flexibility to switch between different products quickly, allowing manufacturers to adapt to changing market conditions without extensive downtime.

Quality and Purity: Given their specialized applications, the quality and purity of specialty chemicals are paramount. Batch processing allows rigorous quality control at the end of each production cycle, ensuring the product meets stringent standards. If an issue arises in one batch, it doesn’t compromise the entire production.

Customization: Many specialty chemicals are produced based on specific client requirements. Batch processes can be easily customized to produce unique formulations or variants of a product, catering to each client’s specific needs.

Economic Considerations: Setting up a continuous processing system can involve significant capital expenditure. Given the “smaller” production volumes and the diverse range of products in the specialty chemicals sector, the return on investment for continuous systems might only sometimes be justifiable. Batch processes, often requiring lower initial investment, can be more economically viable for this sector.

Scale In Response to Demand: Whereas a continuous system must be designed for a specific capacity at inception, this is not the case with batch processing. It is common to “scale up” a system to meet current and “near” future market demand. If market demand accelerates, one can quickly “scale out” by duplicating production lines. This approach is often significantly more capital efficient, especially when future demand is uncertain.

Safety:: Some specialty chemical reactions might be hazardous if scaled up for continuous processes. Batch processing can sometimes offer a safer environment by limiting the quantity of reactive chemicals in the system at any given time.

In essence, the unique challenges, and requirements of the specialty chemicals sector, ranging from the intricacies of the synthesis processes to market dynamics, make batch processing a fitting and often preferred choice for manufacturers.

Why Batch Processing Dominates Nanomaterial Manufacturing

Nanomaterials are driving breakthroughs across diverse fields due to their inherent behavioral properties. And yet, the very features that make them unique – their minute size, enhanced surface area, and quantum effects – also make their synthesis a complex affair. It’s no surprise, then, that the manufacturing of these materials has a strong predilection for batch processing. Let’s explore the factors intrinsic to nanomaterials that make batch processing the dominant choice.

Precision in Nucleation and Growth. Nanomaterials, by virtue of their size, exhibit extreme sensitivity to the conditions in which they are formed. The initiation of nanoparticle formation (nucleation) and their subsequent growth are critically dependent on parameters such as temperature, concentration gradients, and pH levels. Batch processing offers an environment where these conditions can be defined, controlled, and replicated with high precision, ensuring consistent nucleation and growth dynamics unique to specific nanomaterials.

Multi-step Synthesis Routes. Many nanomaterials require intricate, multi-step synthesis processes where each stage demands distinct conditions. In continuous processing, maintaining the dynamic changes needed for each stage can be challenging. Conversely, batch processing allows for the isolation, purification, and validation of intermediates at each juncture, ensuring successful transitions between synthesis stages tailored for nanoscale materials.

Safety and Containment. Given their heightened reactivity due to increased surface area-to-volume ratios, nanoparticles can pose specific safety concerns. Batch processes, in their enclosed design, significantly mitigate risks associated with nanoparticle exposure, unintended releases, or agglomeration that can occur in open or extended systems.

Characterization and Quality Assurance. Post-synthesis characterization of nanomaterials is vital. Techniques such as transmission electron microscopy, X-ray diffraction, or spectroscopy are used to ensure the desired size, shape, and properties are achieved. Batch processing facilitates this by allowing a complete analysis of each batch, serving as a quality checkpoint, and ensuring the unique attributes of nanomaterials are preserved and consistent.

Handling of Temperamental Precursors. The synthesis of certain nanomaterials involves precursors or reagents that can be extremely sensitive to external conditions like light, air, or temperature fluctuations. The confined environment of batch reactors ensures the stability and efficacy of these precursors throughout the synthesis process, crucial for the desired nano-properties.

Economic Considerations. While nanomaterials hold immense promise, many applications are still in nascent stages or cater to niche markets. The investment required for continuous production systems, given the complexities associated with nanoscale, may not always be justified by the demand or volume. Batch processes, on the other hand, offer modularity, scalability, and adaptability tailored to the ever-evolving world of nanomaterials.

While batch processing’s dominance in nanomaterial manufacturing arises from a confluence of factors, it’s clear that the unique challenges and requirements presented by the nanoscale play a central role. As the science of nanomaterials advances, and as we continually push the boundaries of what’s possible, the adaptability and precision of batch processing will remain invaluable. However, there’s always room for improvement.

Enter the Hybrid Batch Manufacturing Approach to Nanomaterial Manufacturing

Hybrid batch manufacturing integrates both batch and continuous processing techniques, aiming to harness the strengths of each while mitigating their limitations. By strategically employing each method at specific stages of production, manufacturers can achieve optimized results. Cerion Nanomaterials exemplifies this approach, adopting it in response to its expanding customer base, which increasingly seeks enhanced processing capabilities and larger production volumes. A deeper dive into the comparative advantages of the hybrid approach demonstrates:

Integrating Stages. In hybrid systems, specific stages of a process might be continuous, while others remain batch-oriented. For example, a raw material could be processed continuously until a particular intermediate is formed, after which the material might be subjected to batch processes for final modifications and purification.

Flexibility. Hybrid systems offer operational flexibility. For instance, in chemical synthesis, the initial reaction stages are often more suitable for batch processing where the reaction conditions can be precisely controlled and adjusted in real-time. Whereas subsequent post-processing of the nanomaterial, such as calcination, might be more suitable for continuous processing due to steady-state conditions, better heat management, and improved yield.

Scalability. Combining continuous and batch modes can offer easier scale-up. The continuous stages can be scaled by extending operating time, while batch stages can be scaled by volume or through parallel batch units.

Quality and Control. The continuous segments of hybrid systems can provide consistent quality due to steady-state operations. Batch segments, meanwhile, allow for tighter control over specific stages, accommodating processes that might be difficult to maintain continuously.

Economic Considerations. By integrating continuous processes where they are most advantageous, one can achieve reduced operational costs, better resource utilization, and potentially higher throughput. The batch stages, on the other hand, can cater to processes that may not be economically viable to run continuously due to equipment costs, setup times, or intermittent demand.

Safety and Environmental Factors. Continuous segments can reduce waste generation and offer better control over exothermic reactions due to consistent operating conditions. Batch segments, meanwhile, provide the option of isolation, which can be crucial for handling hazardous reactions or for processes that require specific inert environments.

Summary

While the broader narrative in specialty chemicals and nanomaterial manufacturing has been largely dominated by batch processing, it’s important to recognize that there are always exceptions that challenge the norm. There are indeed certain materials that are effectively produced through continuous processes. These achievements, notable in their own right, showcase the adaptability and innovation inherent in the field. However, despite these notable exceptions, continuous processing remains an outlier in this domain. For a majority of specialty chemicals and nanomaterials, the complexities of their synthesis, combined with the need for precise control and adaptability, often render batch processing a more suitable, pragmatic and economically appropriate choice both for the manufacturer and more importantly, their customers.

References

¹ An FDA self-audit of continuous manufacturing for Drug Products. U.S. Food and Drug Administration. (2023, July 31). https://www.fda.gov/drugs/cder-small-business-industry-assistance-sbia/fda-self-audit-continuous-manufacturing-drug-products#:~:text=At%20the%20start%20of%202022,finished%20solid%20oral%20drug%20products.

² Chen, R., Hwang, C., Lee, K., Zydney, A., Kokai-Kun, J. F. (2022, December 5). Where Do We Stand On Adopting Continuous Manufacturing For Biologics? Bioprocess Online. https://www.bioprocessonline.com/doc/where-do-we-stand-on-adopting-continuous-manufacturing-for-biologics-0001

³ Jhamb, K. (2019). CONTINUOUS MANUFACTURING – Continuous Manufacturing in Pharmaceuticals: Implications for the Generics Market. Drug Development & Delivery. https://drug-dev.com/continuous-manufacturing-continuous-manufacturing-in-pharmaceuticals-implications-for-the-generics-market/

⁴ In 2023, The Global Polyethylene Production Capacity Will Exceed 157 Million Tons Per Year, And China’s Growth Rate Will Top The List. ECHEMI. (2022, February 14). https://www.echemi.com/cms/487375.html

⁵ IEA (2021), Ammonia Technology Roadmap, IEA, Paris https://www.iea.org/reports/ammonia-technology-roadmap, License: CC BY 4.0

⁶Titanium dioxide capacity will break 6 million tons this year! Industry warning: highly concerned about overcapacity and titanium raw material shortage. ECHEMI. (2023, April 7). https://www.echemi.com/cms/1325256.html#:~:text=In%202022%2C%20the%20total%20effective,capacity%20utilization%20rate%20is%2083.28%25.

⁷ Pelley, J. (2020, February 12). Number of chemicals in commerce has been vastly underestimated. Chemical & Engineering News. https://cen.acs.org/policy/chemical-regulation/Number-chemicals-commerce-vastly-underestimated/98/i7

⁸OECD Environmental Outlook for the Chemicals Industry. ORGANISATION FOR ECONOMIC CO-OPERATION AND DEVELOPMENT. (2001). https://www.oecd.org/env/ehs/2375538.pdf