Which Storage Medium Has the Lowest Embodied CO₂ per Terabyte?

As sustainability becomes a core consideration in data center planning, IT leaders are asking a key question: Which storage technology has the lowest carbon footprint per terabyte?

While lifecycle power use is often discussed, embodied CO₂ – the emissions generated during manufacturing – can be equally important when evaluating hardware impact.

Let’s break down how hard drives (HDDs), solid-state drives (SSDs), and magnetic tape (like LTO) compare in both embodied carbon and lifecycle emissions, and what this means for infrastructure choices.

Understanding Embodied CO₂ vs. Lifecycle Carbon

• Embodied CO₂ refers to the greenhouse gas emissions released during the manufacture of a product – materials, energy, transport, and factory processes.
• Lifecycle carbon includes everything: manufacturing + operation (power used during life) + end-of-life disposal or recycling.

While lifecycle emissions dominate long-term power-hungry systems like servers or GPUs, for cold or archival storage, embodied CO₂ becomes more relevant – especially if the media is idle most of its lifespan.

SSD: Fast, Durable – and Carbon Intensive to Manufacture

SSDs offer superior performance and durability, but at a high carbon cost in production. According to data from multiple life cycle analyses:

• 1 TB of SSD storage can embody 200-400 kg CO₂-eq, depending on NAND density and packaging.
• Semiconductor fabrication (especially NAND flash) is extremely energy-intensive due to photolithography, etching, doping, and cleanroom requirements.
• SSDs have fewer moving parts but more silicon – and silicon is carbon-heavy to produce.

This makes SSDs the highest in embodied CO₂ per terabyte, especially for enterprise NVMe and large-capacity QLC drives.

HDD: Mechanically Complex, but Surprisingly Efficient per TB

Hard disk drives, despite their motors and magnetic platters, have moderate embodied carbon levels. Their advantage lies in:

• Mechanical scalability: a 22-28 TB HDD shares most of its components with a 4-6 TB unit, spreading emissions across more capacity.
• Typical embodied CO₂ is 50–100 kg per drive, or 2-4 kg CO₂ per TB for high-capacity models.
• Lower reliance on high-purity semiconductors reduces upstream energy usage.

In terms of embodied carbon per terabyte, HDDs typically outperform SSDs by a factor of 5–10×.

Tape (LTO): Efficient in Use, But What About Manufacture?

Tape has long been celebrated for energy-efficient use:

• Tapes stored on shelves use zero power when idle.
• A 2022 analysis from the IEEE and industry sources shows LTO tape can emit as little as 0.07 kg CO₂ per TB-year, including operation.

But when it comes to embodied CO₂:

• Each LTO cartridge has relatively low emissions (approx. 5–10 kg CO₂), but only holds up to 18–30 TB uncompressed.
• Tape drives themselves are complex, high-precision devices that are amortized across fewer terabytes than HDDs.
• Overall, HDDs may actually beat tape in embodied CO₂ per TB, especially at high drive capacities (e.g. 26–28 TB HDD vs. 18 TB tape).

However, tape wins over HDDs in lifecycle CO₂ if the workload is cold (rarely accessed), because spinning disks draw continuous power.

Quick Comparison: Embodied CO₂ per Terabyte

Key Takeaways

• SSD is worst in embodied CO₂ per TB due to semiconductor manufacturing.
• HDD has the best balance of low embodied CO₂ and capacity scaling, especially for active archive or warm storage tiers.
• Tape wins on lifecycle CO₂, but not necessarily on embodied CO₂ per TB, especially when including drive infrastructure.
• For cold storage, tape or spin-down HDDs (like Leil ’s ICE model) offer the best environmental tradeoff.
• For active, high-performance workloads, SSD is justifiable despite its carbon cost -but it should be reserved for IOPS-sensitive tiers.

Conclusion

If your goal is to minimize embodied carbon per terabyte, high-capacity HDDsare the best option across most storage tiers. They’re significantly greener than SSDs to manufacture and may even edge out tape if the workload isn’t 100% cold.

However, for deep archive, tape remains the winner in total lifecycle efficiency. And when random performance is non-negotiable, flash is necessary, albeit carbon-expensive.

The optimal approach? Use each technology where it excels:

Author: David Gerstein
David Gerstein is the CTO of Leil, an Estonia-based storage infrastructure company building HDD-native software for the exabyte era. Leil is in active co-engineering partnership with Western Digital, validated across the WD, Seagate, and Toshiba drive ecosystems.