Embodied carbon and circularity

The concrete, steel, copper, aluminum, generators, chillers, batteries and servers that make up a data centre all carry emissions from their extraction, manufacture and transport, long before the facility uses its first kilowatt-hour. This embodied carbon was long overlooked because operational emissions were so much larger. As data centres move to clean electricity, the balance changes: on a clean grid, embodied carbon can be the larger part of a facility's lifetime footprint, and it is emitted up front, when it matters most for climate goals. Alongside carbon, data centres consume large quantities of materials and generate electronic waste as hardware is replaced. This lesson covers how embodied carbon is measured, where it comes from in buildings, equipment and IT, how to reduce it, and the principles of circularity: designing out waste and keeping materials in use.

Measuring embodied carbon

Embodied carbon is estimated with life cycle assessment (LCA), which accounts for emissions across a product's life stages: raw material extraction and manufacturing (the product stage), transport and construction, use (including maintenance and replacement), and end of life. For buildings, the European standard EN 15978 and the international ISO 21930 and ISO 14040/14044 define methods and stage modules (A1 to A3 for products, A4 and A5 for transport and construction, B for use, C for end of life, D for benefits beyond the life cycle). Product-level data come from environmental product declarations (EPDs), third-party verified documents reporting a product's impacts per unit, now widely available for concrete, steel, insulation and increasingly for electrical and mechanical equipment. Where EPDs are unavailable, industry-average databases or spend-based estimates are used, with greater uncertainty.

Whole-building LCA tools combine material quantities from the design with EPD or database factors to estimate embodied carbon, allowing designers to compare structural systems, materials and equipment choices before construction, when changes are cheapest.

Where embodied carbon comes from

In a data centre, embodied carbon arises in three main areas:

• The building: concrete foundations, slabs and walls; structural steel; roofing; envelope; and site works. Concrete and steel dominate, through cement production and steelmaking.
• Mechanical, electrical and plumbing (MEP) equipment: switchgear, transformers, UPS systems, batteries, generators, chillers, air handlers, pipework, cable and busway. Copper and aluminum in cables and busbars, and the steel in equipment, are significant, and MEP equipment is replaced one or more times during the building's life.
• IT equipment: servers, storage and networking, with high embodied carbon per kilogram because of semiconductors, printed circuit boards and memory, and short lives of three to six years, so they are replaced many times over a facility's life.

# Embodied versus operational carbon over a 20-year life for a 20 MW (IT) facility (illustrative values)
years = 20
building_t = 25000            # structure, envelope, site works
mep_t = 30000                 # electrical and mechanical equipment, replaced once mid-life
it_refresh_t = 9000 * 1.3     # 9,000 servers at about 1.3 t each, refreshed every 5 years
annual_MWh = 20 * 8760 * 0.8 * 1.25

embodied = building_t + mep_t * 2 + it_refresh_t * (years // 5)
for grid_name, g in [("average grid, 380 g/kWh", 380), ("clean grid, 30 g/kWh", 30)]:
    operational = annual_MWh * g / 1000 * years
    share = embodied / (embodied + operational)
    print(f"{grid_name:<26} operational {operational:>9,.0f} t, embodied {embodied:>7,.0f} t, embodied share {share:5.1%}")

# Effect of lower-carbon concrete and steel (30 % less building carbon) and server life extension to 7 years
improved = building_t * 0.7 + mep_t * 2 + it_refresh_t * (years / 7)
print(f"With low-carbon structure and 7-year servers: embodied {improved:,.0f} t ({1 - improved / embodied:.0%} less)")

average grid, 380 g/kWh    operational 1,331,520 t, embodied 131,800 t, embodied share  9.0%
clean grid, 30 g/kWh       operational   105,120 t, embodied 131,800 t, embodied share 55.6%
With low-carbon structure and 7-year servers: embodied 110,929 t (16% less)

On an average grid of 380 g/kWh, operational emissions over 20 years are about 1.3 million tonnes and embodied carbon is less than a tenth of the total. On a clean grid of 30 g/kWh, operational emissions fall to about 105,000 t, and embodied carbon, about 130,000 t, becomes more than half of the lifetime footprint. IT hardware, refreshed every five years, accounts for about a third of the embodied total in this example. Lower-carbon structural materials and extending server life to seven years together cut embodied carbon by about 16 %.

Reducing embodied carbon in the building

Measures that reduce the embodied carbon of the building include:

• Using less material: efficient structural design, avoiding over-specification of concrete strength and thickness, and right-sizing foundations.
• Lower-carbon concrete: replacing part of the cement with supplementary cementitious materials such as fly ash, slag or calcined clay; using blended cements (such as Portland-limestone cement); specifying performance-based mixes; and in some cases using concrete that absorbs CO₂ during curing.
• Lower-carbon steel: specifying steel made in electric arc furnaces from recycled scrap, which typically has much lower emissions than steel from blast furnaces.
• Alternative structures: mass timber (cross-laminated timber and glulam) for offices and some data hall structures, with fire protection designed accordingly; several operators have built timber-framed data centres.
• Reuse: adapting existing buildings rather than building new, and designing for disassembly so components can be reused at end of life.

In Canada, the federal government's Standard on Embodied Carbon in Construction requires embodied carbon reporting and reduction for major federal construction projects, and the National Research Council has developed national guidelines for whole-building LCA. Portland-limestone cement (type GUL) is widely used, reducing cement emissions by around 10 %, and several provinces and municipalities, such as Toronto through its Green Standard, are introducing embodied carbon limits for new buildings.

Reducing embodied carbon in equipment and IT

For MEP equipment, the main levers are right-sizing (not installing capacity that will never be used), modular designs that add capacity as needed, specifying equipment with EPDs and lower-carbon materials, extending equipment life through maintenance and refurbishment, and choosing refrigerants with low GWP (Lesson 4). For IT, they include extending server lives where performance per watt allows (Lesson 5), reusing components such as memory, drives and chassis across generations, buying refurbished equipment for less demanding workloads, and designing infrastructure that does not force premature replacement. Open hardware designs, such as those developed by the Open Compute Project, emphasize modularity and serviceability, which support longer lives and component reuse.

Circularity and electronic waste

A circular economy aims to keep products and materials in use at their highest value for as long as possible, through maintenance, reuse, refurbishment, remanufacturing and, finally, recycling. Data centres retire large volumes of IT hardware, batteries and equipment. Responsible end-of-life practice includes:

• Secure data sanitization or destruction of storage media, verified and documented, so that equipment can be reused without data risk.
• Resale or redeployment of working equipment, through internal reuse or certified IT asset disposition (ITAD) providers.
• Harvesting of usable components for spares.
• Certified recycling of the remainder, recovering metals including copper, gold and rare elements, and handling hazardous materials safely. Certifications such as R2 and e-Stewards set standards for electronics recyclers.
• Battery recycling: lead-acid batteries are recycled at very high rates; lithium-ion recycling is growing, and second-life uses for batteries are emerging.

Metrics help: the share of retired equipment reused or refurbished, the share of material recycled, and waste sent to landfill. Contracts with suppliers can require take-back and recycled content.

Embodied carbon in procurement

Because most embodied carbon is locked in by purchasing decisions, procurement is where reductions happen. Owners increasingly include embodied carbon in tender requirements: asking contractors for EPDs of major materials, setting maximum global warming potential values for concrete and steel, requiring suppliers of switchgear, generators, UPS and cooling equipment to provide product carbon footprints, and asking IT vendors for product carbon footprints and take-back commitments. Weighting embodied carbon in bid evaluation, alongside price and quality, rewards suppliers who invest in lower-carbon products. Industry groups have begun to standardize product category rules for data centre equipment, which will make comparisons more reliable.

Longer-lived, adaptable buildings

A data centre building lasts far longer than the equipment inside it, but technology changes quickly: rack densities have risen from a few kilowatts to over 100 kW, and cooling has shifted from air to liquid. Buildings designed for flexibility, with structural capacity for heavier equipment, space and routes for liquid cooling pipework, and electrical infrastructure that can be upgraded in modules, can be adapted rather than replaced, saving the embodied carbon of new construction. Adaptability is therefore a sustainability feature, even if it adds some cost at the start.

Finally, end-of-life planning for the building itself, documenting materials and connections so that components can be recovered, prepares for a future in which construction materials are increasingly reused.

Embodied carbon is also increasingly reported. Customers ask for the embodied emissions of the capacity they lease, investors look for whole-life carbon in green building certifications, and building codes in several jurisdictions now require whole-building LCA for large projects. Operators who measure embodied carbon early, using design-stage LCA tools, can respond to these requests with evidence and can show reductions achieved through design choices.