The Carbon Footprint of FRP vs Steel: What the Numbers Actually Mean
The claim appears regularly in FRP industry literature: pultruded GFRP produces 60 to 70% lower CO₂ emissions per tonne than primary steel. It is not wrong. But it is also not the complete picture, and understanding what it actually means — which boundaries it uses, what it leaves out, and where the comparison genuinely favours FRP — is more useful than repeating the headline number without context. This blog explains the carbon comparison between FRP and steel properly.
Published by Reinforce Technology | 12 August 2026
Life cycle assessment (LCA) is the methodology used to quantify the environmental impact of a product across its full life cycle, from raw material extraction through manufacture, use, and end of life. The methodology is standardised under ISO 14040 and ISO 14044 and produces results expressed in global warming potential (GWP), measured in kilograms of CO₂ equivalent (CO₂e) per declared unit — usually per kilogram of material, per metre of section, or per functional unit of the application being assessed.
The comparison between FRP and steel is typically made at the cradle-to-gate stage of the LCA — covering raw material extraction and manufacturing up to the factory gate, before the product leaves for the construction site. This is the most widely available and most comparable LCA boundary for building materials in the UK, corresponding to modules A1 to A3 in the EN 15804 Environmental Product Declaration framework. Understanding why the comparison is typically made at this boundary, what it includes, and what the full picture looks like when the comparison is extended through the use phase and end of life, is the foundation of an informed reading of any FRP versus steel carbon claim.
The Cradle-to-Gate Numbers
Primary steel produced at a blast furnace using iron ore and coking coal generates approximately 1.85 tonnes of CO₂e per tonne of steel produced, based on World Steel Association data for integrated blast furnace-basic oxygen furnace steelmaking. This is the manufacturing carbon intensity of primary steel — the steel made from ore rather than from recycled scrap. Electric arc furnace steel, made predominantly from recycled scrap using grid electricity, generates approximately 0.4 to 0.6 tonnes of CO₂e per tonne, depending on the carbon intensity of the electricity grid supplying the furnace. In the UK, where the electricity grid carbon intensity has fallen substantially with the growth of renewable generation, electric arc furnace steel made on UK grid electricity in 2026 has a substantially lower cradle-to-gate carbon footprint than UK primary steel or imported primary steel.
Pultruded GFRP manufacturing emissions range from 1.8 to 4.6 tonnes of CO₂e per tonne of finished profile, based on peer-reviewed lifecycle assessment data (ScienceDirect, 2025). This range is wide and meaningful. It reflects real variability in production processes: the energy intensity of the glass fibre melting process (which requires temperatures above 1,400°C), the resin system used (vinyl ester resins have higher embodied energy than polyester), the production scale (larger pultrusion facilities achieve better energy efficiency per unit output), and the carbon intensity of the electricity grid supplying the manufacturing facility.
The comparison gets more complex when electric arc furnace steel is used as the steel baseline. EAF steel at 0.4 to 0.6 t CO₂e/t has lower cradle-to-gate emissions than mid-range GFRP at 2 to 3 t CO₂e/t. On a per-kilogram-of-material basis at cradle to gate, EAF recycled steel can have a lower manufacturing carbon footprint than pultruded GFRP. This is the honest version of the comparison, and it is important context for understanding where the FRP environmental advantage actually lies.
Why Per-Kilogram Is the Wrong Unit for Most Applications
Comparing materials by their carbon footprint per kilogram is the right starting point but the wrong ending point for most structural applications. What matters in practice is the carbon footprint of the structural function — the load carried, the span bridged, the perimeter fenced, the cable management length installed — not the raw weight of material used to perform it.
Pultruded GFRP is approximately 75% lighter than structural steel. An FRP I-beam that performs the same structural function as a steel I-beam at the same span and loading uses less material by weight, because the structural performance of FRP in the applications where it is typically used — secondary framing, cable tray supports, walkway primary beams — is achieved at substantially lower mass than the equivalent steel section. When the comparison is made per unit of structural function rather than per kilogram, the FRP carbon position improves relative to steel even where per-kilogram comparisons are less favourable.
A peer-reviewed cradle-to-grave LCA comparing GFRP rebar to steel rebar found that while the per-kilogram emissions difference was 17%, the emissions reduction in real-world construction scenarios — where GFRP's lower density allows less material to be used for equivalent structural performance — ranged from 77 to 85% (ScienceDirect, 2025). This is the most important LCA finding for FRP applications: the functional unit comparison, which accounts for the lower mass of FRP needed to do the same job as steel, produces a substantially more favourable environmental outcome than the per-kilogram comparison that headline figures usually cite.
What Cradle-to-Gate Leaves Out
Cradle-to-gate LCA stops at the factory gate. It does not include transport to site, installation carbon, use-phase emissions, maintenance carbon, or end-of-life processing. For the FRP versus steel comparison, several of these excluded phases are significant.
Use-Phase Maintenance Carbon
This is the most important excluded phase for the FRP versus steel comparison in infrastructure applications. Steel secondary infrastructure in corrosive environments requires periodic recoating to maintain its protective zinc coating. Each recoating event consumes materials and energy with their own carbon footprint: the manufacture of the coating system, the transport of materials and contractors to site, the operation of surface preparation and coating application equipment, and the disposal of surface preparation waste. In demanding environments — coastal, water treatment, marine, chemical — steel secondary infrastructure may require recoating every 8 to 15 years, generating two to four recoating events across a 30 to 50-year asset life.
FRP secondary infrastructure in the same environments requires no recoating. The use-phase maintenance carbon of FRP is zero. When maintenance carbon is included in the comparison, the total life cycle carbon of FRP secondary infrastructure is lower than equivalent steel secondary infrastructure in corrosive environments, even in cases where the cradle-to-gate manufacturing comparison is less strongly in FRP's favour. The UK Net Zero Carbon Buildings Standard, which requires whole-life carbon assessment for large commercial buildings, mandates that this maintenance carbon be included in the embodied carbon calculation — making the FRP position in NZCBS compliance assessments better than a cradle-to-gate-only view suggests.
Transport and Installation Carbon
FRP's lower weight reduces the transport carbon of delivering materials to site, because lighter loads require less fuel to transport and enable more material to be carried per vehicle. This benefit is proportional to the transport distance and the weight differential — typically 75% less material mass for equivalent structural function — and is more significant for large-scale infrastructure projects where material delivery involves substantial vehicle movements. Installation carbon is also reduced by FRP's lighter weight, because manual installation without mechanical lifting equipment requires less plant fuel consumption than equivalent steel installation with cranes and forklifts.
End of Life
This is the most genuinely difficult phase for FRP in the carbon comparison. Steel is one of the most recycled materials in the world, with well-established collection, processing, and remelting infrastructure that recovers steel at high efficiency and routes it back into primary or secondary steel production. The recycled content of steel used in UK construction already partially offsets its manufacturing carbon, and the recyclability of steel at end of life is a genuine environmental credit.
FRP does not have equivalent end-of-life infrastructure. Mechanical recycling of FRP — grinding the cured composite into particulate that can be used as filler in new composite products — is commercially available but degrades the fibre length and produces a lower-performance recyclate than virgin glass fibre. Pyrolysis, which thermally decomposes the polymer matrix and recovers the glass fibre in a condition suitable for reuse, is available at small scale but not yet commercial at infrastructure volumes in the UK. Cement co-processing, in which FRP waste is used as a fuel and raw material substitute in cement kiln operations, provides an energy recovery route but not material recovery. The honest assessment of FRP end-of-life is that it is more complicated than steel recycling, generates landfill waste where recycling infrastructure is unavailable, and is an active area of industry and academic research without a fully resolved commercial solution (Magonde, 2025).
For the carbon comparison specifically, the end-of-life credit for steel recycling partially offsets steel's higher manufacturing carbon. How much it offsets depends on the recycling rate achieved, the energy intensity of the recycling process, and the carbon credit methodology applied. In a conservative whole-life carbon assessment that gives steel full end-of-life recycling credit and gives FRP no end-of-life credit, the advantage of FRP over primary steel narrows compared with a cradle-to-gate only comparison. In a comparison against EAF recycled steel with full recycling credit, the per-kilogram whole-life position of FRP and steel can be close depending on the specific scenario and the energy grid assumptions.
Where the FRP Carbon Advantage Is Clearest
Having laid out the honest complexity of the comparison, it is equally important to identify where the FRP carbon position is most clearly and robustly favourable.
The clearest FRP carbon advantage is in applications where steel secondary infrastructure requires maintenance recoating across the asset life. In these applications — which include most coastal, marine, water treatment, and chemical infrastructure environments — the use-phase maintenance carbon of steel adds substantially to its whole-life carbon, while FRP's use-phase maintenance carbon is zero. When maintenance carbon is properly accounted for in a whole-life assessment, FRP's whole-life carbon position is better than a cradle-to-gate comparison suggests, in some cases significantly so.
The second clearest advantage is in weight-sensitive applications where the lower mass of FRP needed to achieve equivalent structural function makes the functional unit comparison substantially more favourable than the per-kilogram comparison. For applications where FRP structural sections are 25 to 40% of the mass of equivalent steel sections — which covers most secondary framing, cable tray support, and access system applications — the per-functional-unit carbon of FRP is substantially lower than per-kilogram comparisons indicate.
The third advantage is against primary blast furnace steel in the cradle-to-gate comparison specifically, which remains the most relevant comparison for infrastructure using primary steel rather than recycled-content steel. UK infrastructure steel is not uniformly high recycled content — procurement specifications for some applications require primary-grade steel properties — and for these applications the cradle-to-gate comparison between GFRP and primary steel shows the advantage that the 60 to 70% figure describes.
What an Environmental Product Declaration Tells You
An Environmental Product Declaration (EPD) is a standardised document, produced under EN 15804 and verified by a third party, that reports the lifecycle assessment results for a specific product across defined LCA modules. For FRP structural profiles, an EPD would report the global warming potential for modules A1 to A3 (cradle-to-gate manufacturing), and optionally for A4 (transport to site), A5 (installation), B1 to B7 (use phase, including maintenance), and C1 to C4 (end of life). The UK Net Zero Carbon Buildings Standard requires EPD-based embodied carbon data for materials used in NZCBS-compliant buildings, making EPDs increasingly important procurement documentation for UK infrastructure projects.
An EPD for a pultruded FRP structural profile produced to EN 15804 by a verified third-party certifier (BRE, BREEAM Services, or an International EPD System certifier) is the highest-quality form of embodied carbon data currently available for FRP materials, and the form of data that NZCBS compliance assessments and sophisticated green building certifications require. Not all FRP manufacturers have produced EPDs for their products, and the absence of a verified EPD means that embodied carbon data must be taken from generic datasets such as the Inventory of Carbon and Energy (ICE) or the EcoInvent database — which introduce more uncertainty than product-specific verified data.
The Honest Summary
The carbon comparison between FRP and steel is genuinely context-dependent, and the contexts where FRP performs best are also the contexts where it is most commonly specified: corrosive environments with long design lives and maintenance-intensive steel alternatives. In those contexts — coastal, marine, water treatment, chemical processing, and demanding outdoor infrastructure — the whole-life carbon of FRP secondary infrastructure, including zero use-phase maintenance carbon, is lower than equivalent steel secondary infrastructure across 30 to 50-year asset lives even when the end-of-life recycling credit for steel is fully applied.
In contexts where EAF recycled steel with high recycled content is the steel alternative, the per-kilogram manufacturing comparison is less clearly in FRP's favour. The functional unit comparison, accounting for FRP's lower mass in equivalent structural applications, restores much of the advantage. And the maintenance-free use phase of FRP restores the rest in environments where steel requires periodic recoating.
The 60 to 70% lower manufacturing emissions figure is valid for the comparison it makes — pultruded GFRP at the lower end of its production range against primary blast furnace steel, cradle to gate, per kilogram. It is a starting point for understanding the environmental position of FRP, not the complete picture. The complete picture, properly accounted for across a realistic infrastructure application with a 30 to 50-year design life in a corrosive environment, is broadly consistent with the headline figure — and in some maintenance-intensive applications, more favourable still.
References
Energies (2023) 'Steel, Aluminum, and FRP-Composites: The Race to Zero Carbon Emissions', Energies, 16(19), p. 6904. doi: 10.3390/en16196904. [Rajulwar et al.; carbon tax competitiveness; cradle-to-gate LCA comparison across structural materials].
Frontiers in Built Environment (2023) 'A comparative life cycle assessment of fiber-reinforced polymers as a sustainable reinforcement option in concrete beams', Frontiers in Built Environment. doi: 10.3389/fbuil.2023.1194121. [GFRP bar cradle-to-gate shows most significant environmental impact reduction versus steel and CFRP bars].
Magonde, B. (2025) Environmental Impact and Life Cycle Assessment of FRP. MSc Thesis, University of Naples Federico II / MSC FRP. Available at: https://msc-frp.org/wp-content/uploads/2025/10/MSc-Thesis_2024-25_UNINA_BMagonde.pdf [Accessed: 12 August 2026]. [EN 15804 LCA methodology; EPD availability for FRP; variability in CFRP GWP; toxicity categories excluded from standard LCA; end-of-life challenges for FRP recycling].
MDPI Sustainability (2024) 'Comparative Life-Cycle Assessment of Steel and GFRP Rebars for Procurement Sustainability in the Construction Industry', Sustainability, 16(10), p. 3899. doi: 10.3390/su16103899. [GFRP vs steel cradle-to-grave: 17% lower CO₂e per kilogram; 77 to 85% lower CO₂e across spacing configurations in real construction scenarios].
ScienceDirect (2025) 'Sustainable composites for metal replacement: Environmental assessment and material selection of fiber-reinforced polymer across industries', ScienceDirect, doi: 10.1016/S2667-3789(25)00051-3. Available at: https://www.sciencedirect.com/science/article/pii/S2667378925000513 [Accessed: 12 August 2026]. [GFRP emissions 1.8 to 4.6 t CO₂/t; production energy 13 to 32 MJ/kg; GFRP rebar cradle-to-grave 17% lower CO₂e than steel; up to 85.26% lower depending on configuration; EuCIA LCA data for pultruded GFRP].
World Steel Association (2023) Steel's Contribution to a Low Carbon Future and Climate Resilient Societies. Available at: https://worldsteel.org [Accessed: 12 August 2026]. [Blast furnace-BOF primary steel: approximately 1.85 t CO₂e/t; EAF recycled steel: approximately 0.4 to 0.6 t CO₂e/t depending on grid carbon intensity].
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