Circular Discussions: Looking forward to SMST talks on recycling and reprocessing nitinol
At the upcoming SMST conference (May 4-8, 2026), there are two presentations I’m looking forward to that finally open a nitinol can of worms. I’m referring to the talks on recycling and reprocessing of NiTi and NiTiHf by Ms. Sakia Noorzayee (Ruhr University Bochum) and Dr. Othmane Benefan (NASA Glenn Research Center), respectively. SMST is one of the few venues where these conversations happen in the open.
There’s no debate that the benefits of nitinol outweigh the costs in medical device applications where small-scale precision delivers outsized clinical value across millions of procedures each year. The question gets uncomfortable for the nitinol community when the use case calls for kilograms or tonnes per device.
Potential applications of Nitinol in aerospace, automotive, clean technology and construction could increase annual NiTi consumption by an order of magnitude. That drives up demand (and potentially, price), but it would also pull the recyclability conversation out of the lab and into the supply chain. To realize this potential, the nitinol industry needs to be ready to address the same sustainability questions already being asked of other materials.
Why “sustainability” is a tricky question for NiTi
If you ask whether nitinol is a sustainable material, the honest answer is it depends.
If you mean “functional value per gram”, NiTi is the champ. Superelasticity and SME can collapse mechanisms, enable minimally invasive approaches and reduce system complexity (and complication risk).
If you mean “low-impact supply chain, from raw-material to finished component”, NiTi inherits some fundamental realities: titanium is energy intensive in upstream production, nickel production has route-dependent environmental and social risk, and true circular recycling loops for performance-grade NiTi are not mature at any scale.
For the nitinol industry to realize the long-promised potential of larger-scale applications, we need to apply a lifecycle lens to the cost-benefit equation and validate the use case in real terms.
Upstream processing dominates the GWP impact of nitinol
Nitinol is roughly 55% Ni - 45% Ti by weight. Primary Ti-sponge production using the Kroll process is widely recognized as energy-intensive. A recent Nature Communications Earth & Environment analysis reports global average titanium sponge production at approximately 51 kg CO2e/kg (Xun, 2025; Climatiq, 2023; Gao, 2018). Lower energy alternative processes for Ti have been developed, but nothing has moved from R&D to commercial state-of-the-art (U.S. Department of Energy, 2017; Feng, 2023). While raw nickel processing is less energy intensive at 13 kg CO2e/kg (Xun, 2025; Nickel Institute, 2024), the social and environmental impacts continue to be challenging. If we assume a net yield of 85%, the cradle-to-gate impact of raw nitinol can be estimated at 35.5 kg CO2e/kg.
For context, stainless steel cradle-to-gate emissions are 6.8 kg CO2e/kg with a 30% scrap content (World Stainless Association, 2024). Of course, the nitinol industry is about 0.01% the size of the stainless-steel industry, but it’s a clear signal that credible reclamation pathways are required to reduce the dominant impact of upstream raw materials.
A study of downstream processing impacts using NiTi wire
The impact of processing NiTi ingot into semi-finished feedstock is not well documented. However, we can build a reasonable engineering estimate from comparable materials. Let’s assume a wire processing route consisting of VIM-VAR melting, hot work ingot breakdown, multi-stage cold drawing with inter-anneals, and a final straight anneal. The estimated energy intensities for each step are as follows:
| Process | kWh/kg | Reference |
|---|---|---|
| Vacuum Induction Melting (VIM) | 1.2 | (Center for Metals Production, 1987) |
| Vacuum Arc Remelting (VAR, 1x) | 1.2 | (Rudinger, 1984) |
| Hot Working/Breakdown | 0.7 | (Golder Associates Ltd. & Thorn Associates, 2021) |
| Cold Drawing (3x) | 0.15 | (Suliga, 2023) |
| Intermediate Annealing (3x) | 0.6 | (Altınkaynak, 2020) |
| Straight Anneal | 0.3 | (Olsson, 2016) |
| Total Energy Requirements | 4.15 |
Assuming a grid factor of 0.4 kg CO₂/kWh, the downstream processing contributes only 1.7 kg CO2e/kg, less than 7% of the upstream impact, for a total of 37.2 kg CO2e/kg for virgin NiTi wire.
The opportunity
Production of high-purity constituents dominates the burden of downstream processing for virgin nitinol. The opportunity is obvious: increase scrap content in nitinol feedstock and gain a huge reduction in energy intensity. That is difficult because nitinol has a low tolerance for contamination; carbon, oxygen, and nitrogen are the usual suspects. Furthermore, stoichiometry has a huge impact on performance. To avoid downcycling the material, a high degree of discipline in segregation is required.
Because of this, the most realistic recycling loops are closed-loop in-house scrap recycling (which is already happening), or industrial post-process recycling (if waste streams can be carefully managed and certified). Post-consumer recycling is probably still aspirational for nitinol, especially for smaller components and devices.
At present, the academic literature on recycling of nitinol is sparse. There are a handful of studies on the clinical reuse of orthodontic archwires (Kapila, 1992; Potnis, 2011; Shukla, 2024; Gil, 2012). However, only recently has there been any published work on the metallurgical recycling of NiTi, and even then only in the context of powders for additive manufacturing (Sojoodi M. B., 2025a; Sojoodi M. B., 2025b). In industry, machining swarf and trim scrap are almost certainly being remelted by nitinol manufacturers, especially in tube hollow manufacturing, but these practices are not publicly documented because the processes are proprietary and the scrap content in melts must be limited due to oxygen pickup and composition control. We need more discussion and peer-reviewed publication to validate the life-cycle analysis of large-scale clean technology applications.
This LCA highlights the real sustainability bottleneck for NiTi at scale: not processing energy, but circularity and yield. If we want NiTi to move beyond grams into kilograms and tonnes, then the industry has to behave like a bulk metals industry: high-yield conversion, closed-loop scrap management, and sourcing transparency. Without those, large-scale NiTi risks becoming the exact opposite of what its “clean tech” branding implies — a high-embodied-energy alloy deployed at scale where alternatives can achieve similar function with a mature scrap loop and a lower upstream burden.
The SMST community is the perfect group to address this challenge.
References
Altınkaynak, M. Ç. (2020). Energy and Exergy Analysis of an Industrial Annealing Furnace. Süleyman Demirel Üniversitesi Fen Bilimleri Enstitüsü Dergisi, 24(2), 387-393. doi:https://doi.org/10.19113/sdufenbed.678843
Center for Metals Production. (1987). Vacuum Induction Melting Technology. Center for Metals Production. Retrieved from https://p2infohouse.org/ref/09/08921.pdf
Climatiq. (2023). Titanium sponge (titanium sponge production – from titanium tetrachloride): Emission factor. Retrieved March 6, 2026, from climatiq.io: https://www.climatiq.io/data/emission-factor/7322e0cc-4ed5-4f28-a051-3d458ee494fb
Feng, Q. L. (2023). Research Progress of Titanium Sponge Production: A Review. Metals, 13(2), 408. doi:https://doi.org/10.3390/met13020408
Gao, F. N. (2018). Environmental impacts analysis of titanium sponge production using Kroll process in China. Journal of cleaner production, 174, 771-779. doi:https://doi.org/10.1016/j.jclepro.2017.09.240
Gil, F. E. (2012). Variation of the superelastic properties and nickel release from original and reused NiTi orthodontic archwires. Journal of the Mechanical Behavior of Biomedical Materials, 6, 113-119. doi:https://doi.org/10.1016/j.jmbbm.2011.11.005
Golder Associates Ltd., & Thorn Associates. (2021). Canadian Steel Industry Energy & Greenhouse Gas Emissions Intensity, Technology and Carbon Reduction Roadmap. Canadian Steel Producers Association. Retrieved from https://canadiansteel.ca/files/resources/Golder-Report-CSPA-NRCan.pdf
Kapila, S. H. (1992). Load-deflection characteristics of nickel-titanium alloy wires after clinical recycling and dry heat sterilization. American Journal of Orthodontics and Dentofacial Orthopedics, 102(2), 120–126. doi:https://doi.org/10.1016/0889-5406(92)70023-4
Nickel Institute. (2024). Lifecycle data. Sphera. Retrieved from https://nickelinstitute.org/media/fbmdel4y/2025-lifecycledata-executive-summary.pdf
Olsson, S. (2016). Evaluation of a production route for cold-drawn Nitinol wires.
Potnis, S. P. (2011). Effects of recycling on the mechanical properties of nickel–titanium alloy wires: A comparative study. Journal of Indian Orthodontic Society, 45(3), 124-133. doi:https://doi.org/10.5005/jp-journals-10021-1022
Rudinger, K. P. (1984). Experience of Vacuum Arc Melting With Non-Consumable and Consumable Electrodes. Titanium--Science and Technology, 1, 115-121.
Shukla, P. K. (2024). The effect of different clinical recycling methods on load-deflection properties of super-elastic and thermal nickel–titanium orthodontic arch wires: A comparative assessment. Journal of Orthodontic Science, 13(1), 27. doi:https://doi.org/10.4103/jos.jos_200_23
Sojoodi, M. B. (2025)a. Impact of ultrasonic vibration frequency on the quality of produced NiTi. Advanced Powder Technology, 36. doi:https://doi.org/10.1016/j.apt.2025.104945.
Sojoodi, M. B. (2025)b. Integration of Circular Economy into Metal Additive Manufacturing: A Review of Ultrasonic Plasma Atomization for Producing Virgin and Recycled NiTi Powder. Shap. Mem. Superelasticity. doi:https://doi.org/10.1007/s40830-025-00589-y
Suliga, M. W. (2023). Assessment of the Possibility of Reducing Energy Consumption and Environmental Pollution in the Steel Wire Manufacturing Process. Materials, 16(5), 1940. doi:https://doi.org/10.3390/ma16051940
U.S. Department of Energy. (2017). Bandwidth Study on Energy Use. Retrieved from https://www.energy.gov/sites/prod/files/2017/12/f46/Titanium_bandwidth_study_2017.pdf
World Stainless Association. (2024). CO2 Emissions Report. World Stainless Association. Retrieved from https://worldstainless.org/wp-content/uploads/2025/02/worldstainless_CO2_Emissions_Report.pdf
Xun, D. L. (2025). Sustainable supply of critical materials for water electrolysers and fuel cells. Nature, Communications Earth & Environment, 6, 627. doi:https://doi.org/10.1038/s43247-025-02621-6
Yadav A, J. P. (2020). Impact of recycling on the mechanical properties of nickel-titanium alloy wires and the efficacy of their reuse after cold sterilization. Journal of orthodontic science, 9(10). doi:doi: 10.4103/jos.JOS_45_19