In our first dispatch, A Primer: Carbon Nanotubes, we told the journey of CNTs from lab to industry. In The $30 vs $0.13 Problem, we dug into the confusing world of CNT economics, showing how CNTs can range from $40/kg to $8,000/kg depending on structure and purity.
This month I'll cover recycling. It's an interesting technical topic in itself. Only a few years ago, people thought it was impossible to do. Today it's not. That is a good story. But you want to hear a better story? That recycling is not a "green issue". It's not just for ESG and reputation management. No. It's all business.
The story I want to tell today is how recycling nanotubes could change the commercial reality of nanotubes. The economics of recycling suck for plastics and other materials because the resulting recycled material is low-value. Not so, if you can get back nanotubes. As mentioned in last month's edition, you can get $8,000/kg for a (5,5) armchair nanotube. But even more importantly is the cost and time to qualify nanotubes for a new supply chain. I've heard it can take 7 years to qualify CNTs for a Tier 1 automotive OEM. In 7 years, we will have fusion energy. And brain-computer interfaces. We can't wait 7 years. And maybe we won't have to.
Why Recycle Nanotubes?
First, the "forever chemical" concern stems from regulatory anxiety about persistent synthetic materials that don't break down naturally. CNTs could theoretically persist in landfills indefinitely. The irony is that this same chemical robustness makes nanotubes excellent recycling candidates.
Second, CNTs are expensive. Like $8,000/kg for (5,5) armchair nanotubes. Virgin CNT production isn't just costly; it's energy-intensive and heavily dependent on controlled catalytic processes. Every kilogram we recover is a kilogram we don't need to synthesize from scratch.
Third, qualification creates manufacturing's most significant market barrier. Manufacturers exhaustively test samples for dimensional consistency, electrical properties, and integration compatibility. This fundamentally alters recycling economics because recovering already-vetted materials becomes far more valuable than sourcing new supplies that would restart validation, creating technical lock-in where qualified nanotubes become worth recovering at almost any reasonable cost.
Why Is It Hard to Recycle Nanotubes?
Four main challenges: low-loadings, matrix entrapment, regulation, and economics.
First is the low-loading problem. Most CNT-enabled products contain just 0.01% to 1% CNTs by weight. That means recovering a single kilogram of CNTs often requires processing anywhere from 100 kg to 10 tonnes of scrap. The economics are brutal before you even switch the machines on.
Then there's matrix entrapment: CNTs aren't sitting neatly on a surface waiting to be scooped out. They're embedded within polymers, electrodes, or composite matrices at the nanoscale. Separating them without damaging their alignment or introducing contamination remains a non-trivial challenge.
And then regulation. The International Agency for Research on Cancer (IARC) has classified one specific type of CNT as "possibly carcinogenic," while leaving most others unclassified. In Europe, CNTs must meet comprehensive REACH safety requirements. Recycling facilities must navigate EPA pre-approval, enhanced air quality permits, specialized protective equipment, quarterly worker exposure reporting, and specialized waste handling protocols.
Even if you get through all that, there's the question of process economics. The most promising recovery techniques — solvent baths, acid digestion, pyrolysis, or high-temperature reactors — are energy-intensive and capex-heavy.
How Do We Recycle Nanotubes?
For nearly two decades, CNT recycling was considered impossible. In 2024, both IMDEA Materials Institute in Spain and Rice University in the US proved that structured CNT formats can be recovered and reused without performance loss.
1. Crush it: Mechanical Reprocessing
Traditional plastic recycling applied to CNT-filled materials: parts are shredded, melted, and reformed. Studies show composites retain 75-90% mechanical strength after three cycles, but electrical conductivity plummets roughly tenfold per loop as CNTs clump together. Useful today but limited to simple parts where performance degradation is acceptable.
2. Burn it: Thermal Treatment — IMDEA's Breakthrough
Controlled heating to burn away polymer matrices while leaving CNT structures intact. IMDEA Materials Institute demonstrated that CNT sheets can be thermally processed without losing strength or conductivity. Unlike carbon fiber, which suffers catastrophic property loss, CNT sheets act like LEGO bricks — strip the glue, reuse the tower. However, this works cleanly only with pure CNT formats; mixed plastics and electrodes create ash and impurities that degrade CNT quality.
3. Dissolve it: Chemical/Solvent-Based — Rice's "Infinite Fiber Loop"
Using solvents to dissolve CNT fibers back into solution, then spinning them into new fibers. Rice University demonstrated that CNT fibers dissolved in chlorosulfonic acid can be respun into virgin-quality material retaining 100% of tensile strength, conductivity, and alignment. The chemical approach achieved perfect property recovery — a technical marvel — but at the cost of greater process complexity requiring sophisticated solvent handling systems and hazardous chemical safety protocols.
4. Upcycling Plastics: CNTs + Hydrogen
Converting waste plastic feedstock into fresh CNTs using high-temperature pyrolysis or chemical vapour deposition — treating plastic waste as a carbon source for new nanotube synthesis. This could tackle plastic waste and CNT supply simultaneously with multiple revenue streams from processing fees, CNT sales, and hydrogen co-products. The technology is approaching commercial readiness, with some developers targeting deployment within 12-18 months.
Will It Ever Make Economic Sense?
In low-value commodity applications the incentives are weak. Multi-walled CNTs for coatings and conductive plastics cost $30-50 per kilogram, and expanding Asian production capacity is driving those prices even lower. Competing with cheap virgin material in these markets will be difficult for a long time.
Battery manufacturing could be a better application. While CNTs comprise tiny electrode fractions, the intensive qualification requirements make recovery valuable. As gigafactory capacity expands globally, even modest recovery yields from battery recycling could reclaim tens of thousands of tonnes annually.
Premium CNT formats — single-walled nanotubes costing $2,000-8,000 per kilogram, structured fibers, and engineered sheets — operate under a different economic logic. If CNT fibers used in transmission systems or EMI shielding can be recovered and reused, the avoided cost of purchasing new material can justify more advanced recycling processes. Aerospace fuselage skins, lightweight wiring harnesses, and advanced composites are likely to lead adoption.
A second and often more powerful driver is qualification cost. If recovered materials can demonstrate identical properties to the originals, manufacturers bypass costly requalification requirements. In these cases, already-vetted CNTs become more valuable than equivalent new supply, making recycling attractive even as the price of virgin material falls.
The thing I want you to take away from this Dispatch is that recycling is not a sustainability story — it's all economics. Because nanotubes can be so expensive to make and qualify, for some products, it might be economically viable to recycle today. For structured formats like CNT sheets and fibers where thermal and chemical methods are now viable, expect commercial integration likely within 3-5 years across aerospace, EVs, and defense electronics. In these markets, CNTs will evolve from disposable consumables into durable industrial assets, with costs amortized across multiple lifecycles rather than single uses.
So we will begin to see cradle-to-grave, circular economy carbon nanotubes. That's going to be a pretty cool moment. And soon after, we will turn plastics into wonder materials. Thanks for reading.
