GRP Standards: Carbon and Lifecycle
The Carbon Question Is No Longer Optional
Every major infrastructure client in the UK now asks the carbon question. Network Rail asks it. The water companies ask it. The DNOs ask it. The highways authorities ask it. And increasingly, private-sector developers and main contractors ask it too, because BREEAM, LEED, and PAS 2080 demand it.
The question takes different forms, ‘What is the embodied carbon of your product?’, ‘Can you provide an EPD?’, ‘How does this compare with steel on a lifecycle basis?’, but the underlying requirement is the same. Whoever is specifying materials needs independently verified environmental data, and they need to understand what the numbers mean.
This article explains how Environmental Product Declarations work, how to read them, how to avoid the most common errors in comparing materials, and what the numbers actually mean when you put GRP alongside steel for a real-world project. It is the final article in this six-part series, and it is arguably the one that will shape more specification decisions over the next decade than any other.
1. What Is an Environmental Product Declaration?
An Environmental Product Declaration (EPD) is a standardised document that reports the environmental impact of a product based on a Lifecycle Assessment (LCA). It is the environmental equivalent of a nutrition label: it tells you what is inside, how it was measured, and what the numbers mean, using an internationally recognised format.
1.1 The Standards Behind EPDs
| Standard | What It Governs |
| ISO 14040 | Environmental management — Lifecycle Assessment: principles and framework. Defines the methodology for conducting an LCA. |
| ISO 14044 | Environmental management — Lifecycle Assessment: requirements and guidelines. Specifies how to collect data and calculate impacts. |
| ISO 14025 | Environmental labels and declarations — Type III environmental declarations. Defines the EPD format and verification requirements. |
| EN 15804+A2 | Sustainability of construction works — Environmental product declarations: core rules for the product category of construction products. The European standard that defines how construction product EPDs must be structured. |
| ISO 21930 | Sustainability in buildings and civil engineering works — Core rules for environmental product declarations of construction products and services. |
An EPD produced to EN 15804+A2 and verified by an accredited programme operator is the gold standard for construction product environmental data. It is accepted by BREEAM, LEED, PAS 2080, and every major UK infrastructure client.
1.2 What an EPD Contains
A compliant EPD reports environmental impacts across multiple categories, but the one that matters most to specifiers and procurement teams is Global Warming Potential (GWP), measured in kilograms of CO₂ equivalent (kgCO₂eq). This is the product’s carbon footprint.
The EPD also reports other impact categories including ozone depletion potential, acidification potential, eutrophication potential, photochemical ozone creation potential, and abiotic resource depletion. For most construction material selection decisions, GWP is the primary driver.
2. The Lifecycle Stages: Understanding A1 to D
The construction product lifecycle is divided into standardised stages defined in EN 15804. Understanding these stages is essential to reading any EPD correctly.
| Code | Stage Name | What It Covers | GRP vs Steel Relevance |
| A1 | Raw materials | Extraction and processing of raw materials: glass fibres, resin, additives | GRP uses E-glass fibres and petroleum-derived resin. Steel uses iron ore and coking coal. |
| A2 | Transport to factory | Transport of raw materials to the manufacturing facility | Distance from raw material source to factory. Our EPD includes transport to our UK warehouse. |
| A3 | Manufacturing | Energy consumed during manufacturing process | Pultrusion uses electrical energy for die heating and pulling. Steel uses blast furnace energy. |
| A4 | Transport to site | Delivery from factory/warehouse to the construction site | GRP is 75–80% lighter than steel — fewer lorry trips, lower transport emissions per delivered function. |
| A5 | Installation | Energy and waste during installation on site | GRP: manual handling, hand tools. Steel: cranes, welding, hot works. Significant difference. |
| B1–B7 | Use stage | Maintenance (B2), repair (B3), replacement (B4), operational energy (B6), operational water (B7) | This is where GRP transforms the comparison. Zero maintenance vs steel repainting every 7–15 years. No replacement vs steel replacement at 15–25 years in aggressive environments. |
| C1–C4 | End of life | Deconstruction (C1), transport to disposal (C2), waste processing (C3), disposal (C4) | Steel has recycling credit. GRP currently goes to landfill or cement kiln co-processing. Industry working on recycling solutions. |
| D | Beyond lifecycle | Benefits and loads from reuse, recovery, and recycling outside the system boundary | Steel claims credit for recyclability. GRP industry developing chemical recycling and thermoplastic pultrusion routes. |
THE CRITICAL POINT ABOUT LIFECYCLE STAGES
Most EPDs report only stages A1–A3 (cradle to gate). This is the manufacturing carbon footprint only. It does not include transport to site, installation, maintenance, replacement, or end of life. Comparing two materials on A1–A3 alone is like comparing two cars on purchase price alone without considering fuel, maintenance, and resale value. For materials with dramatically different maintenance and replacement profiles — like GRP and steel — the use stage (B1–B7) frequently dominates the total lifecycle impact.
3. The Per-Kilogram Trap: The Single Biggest Mistake in Carbon Comparison
When you compare embodied carbon on a per-kilogram basis, GRP appears to have a higher carbon footprint than steel:
| Material | Embodied Carbon A1–A3 (kgCO₂eq/kg) |
| GRP pultruded profiles | 2.447 kgCO₂eq/kg (ECL EPD, factory gate to UK warehouse) |
| Structural steel (UK average) | 1.55–1.86 kgCO₂eq/kg |
| Galvanised steel | 2.03 kgCO₂eq/kg |
| Stainless steel 316 | 6.15 kgCO₂eq/kg |
On a per-kilogram basis, GRP is approximately 30% higher in embodied carbon than standard structural steel. This is the number that procurement teams see, and it is the number that frequently leads to incorrect conclusions.
Here is why it is wrong to stop at that number:
GRP weighs 75–80% less than steel for equivalent structural function.
A structure that requires 1,000 kg of galvanised steel requires approximately 250 kg of GRP to achieve the same structural performance. The carbon comparison must be made on a functional unit basis — the environmental impact to deliver a defined structural function — not on a per-kilogram basis.
3.1 The Weight-Adjusted Comparison
| Factor | Galvanised Steel | GRP |
| Material required for function | 1,000 kg | 250 kg |
| Embodied carbon per kg | 2.03 kgCO₂eq/kg | 2.447 kgCO₂eq/kg |
| Total embodied carbon A1–A3 | 2,030 kgCO₂eq | 612 kgCO₂eq |
| Carbon saving (functional basis) | — | 70% lower than galvanised steel |
The material that appeared 30% worse on a per-kilogram basis is actually 70% better on a functional basis. This is not a marginal difference — it is transformational.
ALWAYS ASK: WHAT IS THE FUNCTIONAL UNIT?
Any carbon comparison that uses per-kilogram figures without adjusting for the mass required to deliver equivalent structural function is fundamentally misleading. If a supplier or consultant presents a carbon comparison showing GRP as higher carbon than steel, ask one question: is this comparison on a functional unit basis? If it is not, the comparison is invalid.
4. Worked Example: GRP Rebar vs Steel Rebar in a Concrete Slab
This example uses real data from our EPD and demonstrates how the carbon calculation works in practice for a 10m² concrete slab foundation at 150mm thickness.
4.1 The Input Data
| Parameter | Steel Rebar | GRP Rebar |
| Slab area | 10 m² | 10 m² |
| Slab thickness | 150mm | 150mm |
| Concrete volume | 1.50 m³ | 1.13 m³ (25% less — reduced cover) |
| Rebar weight required | 225 kg | 45 kg (80% lighter) |
| CO₂eq per kg (rebar) | 1.86 kgCO₂eq/kg | 2.447 kgCO₂eq/kg |
| CO₂eq per m³ (concrete) | ~320 kgCO₂eq/m³ | ~320 kgCO₂eq/m³ |
4.2 The Carbon Calculation
| Component | Steel Solution | GRP Solution |
| Rebar carbon | 225 kg × 1.86 = 418.5 kgCO₂eq | 45 kg × 2.447 = 110.1 kgCO₂eq |
| Concrete carbon | 1.50 m³ × 320 = 480.0 kgCO₂eq | 1.13 m³ × 320 = 361.6 kgCO₂eq |
| Total carbon | 898.5 kgCO₂eq | 471.7 kgCO₂eq |
| Saving | — | 426.8 kgCO₂eq (47.5% reduction) |
RESULT: 47.5% TOTAL CARBON REDUCTION
Rebar saving: 73.7% (308.4 kgCO₂eq)
Concrete saving: 118.4 kgCO₂eq (reduced cover requirements)
On a single 10m² slab, switching from steel to GRP rebar saves nearly half a tonne of CO₂ equivalent. Scale that across a housing development, a bridge deck, or a water treatment facility, and the carbon savings become project-defining.
5. Worked Example: 100m² Industrial Platform — 50-Year Lifecycle
| Lifecycle Stage | Galvanised Steel Platform | GRP Platform |
| A1–A3: Initial embodied | 650 kg × 2.03 = 1,320 kgCO₂eq | 180 kg × 5.5 = 990 kgCO₂eq |
| A1–A3: Protective coating | 150 kgCO₂eq (galvanising + paint) | 0 |
| A4: Transport to site | 65 kgCO₂eq | 25 kgCO₂eq |
| A5: Installation | 200 kgCO₂eq (crane, welding) | 50 kgCO₂eq (manual, bolted) |
| B2: Maintenance (3 cycles) | 3 × 250 = 750 kgCO₂eq | 50 kgCO₂eq (periodic cleaning only) |
| B4: Partial replacement (year 35) | 1,500 kgCO₂eq | 0 |
| C1–C4: End of life | -400 kgCO₂eq (recycling credit) | +50 kgCO₂eq (disposal) |
| 50-YEAR TOTAL | 3,585 kgCO₂eq | 1,165 kgCO₂eq |
| Saving | — | 67.5% lower whole-life carbon |
Even with steel’s recycling credit at end of life, GRP delivers 67.5% lower whole-life carbon over 50 years in a moderately corrosive environment. The maintenance and replacement stages — which do not appear in a simple A1–A3 comparison — account for over 60% of steel’s total lifecycle carbon.
THIS IS WHY A1–A3 COMPARISONS ARE DANGEROUS
If you compare only manufacturing carbon (A1–A3), steel appears 25% lower than GRP on a per-kg basis. If you compare on a functional unit basis including all lifecycle stages, GRP is 67.5% lower. The difference between these two conclusions is the difference between specifying the wrong material and specifying the right one.
6. Our EPD: How We Calculated It and What It Shows
Engineered Composites’ EPD was developed in conjunction with Composites UK and a professor at the Composites Research Centre and University in Shanghai. It follows ISO 14040, ISO 14044, and reports ISO 14021 self-declared results calculated according to ISO 21930/EN 15804+A2.
6.1 Scope
- Functional unit: 1 kg of GRP pultruded product
- System boundary: Cradle to gate (A1–A3) including transport from manufacturing facility to ECL warehouse in the UK
- Product coverage: All GRP pultruded profiles and gratings manufactured by Engineered Composites
6.2 The Headline Number
Global Warming Potential (GWP)
2.447 kgCO₂eq per kg of product
Cradle to gate (A1–A3) including transport to UK warehouse
6.3 How to Use This Number
To calculate the carbon footprint of any GRP product or order from Engineered Composites:
1. Look up the unit weight of the specific profile or grating from our product data sheets (weight per linear metre for profiles, weight per square metre for grating).
2. Calculate the total weight for the quantity required.
3. Multiply total weight by 2.447 kgCO₂eq/kg.
4. The result is the A1–A3 carbon footprint of your GRP order.
For example: 100 linear metres of 100mm × 100mm × 10mm box section at 3.2 kg/m = 320 kg total weight. Carbon footprint: 320 × 2.447 = 783 kgCO₂eq.
7. How to Compare Fairly: Five Rules for Honest Carbon Comparison
Rule 1: Compare on a functional unit basis
Never compare per-kilogram figures without adjusting for the mass required to deliver equivalent structural performance. GRP is 75–80% lighter than steel for equivalent function — this must be reflected in any comparison.
Rule 2: Include the same lifecycle stages
Rule 3: Use product-specific EPDs, not generic data
Industry-average data can be significantly different from product-specific data. Our EPD states 2.447 kgCO₂eq/kg. Generic GRP figures in databases may range from 4.5 to 6.5 kgCO₂eq/kg. Always use the manufacturer’s specific EPD where available.
Rule 4: Account for concrete savings where applicable
GRP rebar does not require the same concrete cover as steel rebar (because corrosion protection is not needed). This reduces concrete volume by up to 25%, delivering a significant additional carbon saving that should be included in any rebar comparison.
Rule 5: State assumptions transparently
Every carbon comparison involves assumptions: service environment, maintenance frequency, design life, replacement intervals, end-of-life treatment. State them clearly. A comparison that does not state its assumptions cannot be verified or challenged.
8. The Recycling Question: Steel’s Advantage and GRP’s Response
Steel has a genuine advantage at end of life: it is widely recycled, and EPDs can claim a carbon credit in Stage D for the avoided burden of virgin steel production. This credit can be significant — typically 300–500 kgCO₂eq per tonne of steel recycled.
GRP thermoset composites cannot currently be recycled in the same way. The thermoset resin matrix cannot be remelted. Current end-of-life options are:
- Landfill: Widely available but environmentally undesirable. Subject to increasing landfill tax (£103.70/tonne in 2025/26).
- Cement kiln co-processing: Established in the EU, growing in the UK. The GRP is used as both fuel and raw material in cement production, recovering both energy and mineral content.
- Mechanical recycling: GRP is shredded and ground into filler material for use in other products. Limited facilities currently available in the UK.
- Chemical recycling (solvolysis): Emerging technology using solvents or supercritical fluids to break down the resin matrix and recover glass fibres with properties closer to virgin material. Pilot plants operational.
- Thermoplastic pultrusion: Development of pultruded products using thermoplastic matrices (which can be remelted) instead of thermosets offers a route to closed-loop recycling. Products emerging commercially.
The composites industry recognises this challenge and is actively investing in solutions. But it is important to keep the recycling advantage in perspective: even with steel’s end-of-life recycling credit, GRP still delivers lower whole-life carbon in the worked examples above because the savings during the use stage (zero maintenance, no replacement) far exceed the recycling benefit.
9. BREEAM, LEED, and PAS 2080: Where EPDs Earn Credits
| Rating System | Relevant Credits | How GRP EPD Contributes |
| BREEAM | Mat 01 — Lifecycle impacts: credits for specifying materials with lower lifecycle environmental impacts. Mat 03 — Responsible sourcing. Wst 01 — Construction waste. | EPD provides verified data for lifecycle impact calculations. GRP’s durability and reduced maintenance contribute to Mat 01 scoring. |
| LEED | MR Credit — Lifecycle impact reduction. MR Credit — Environmental Product Declarations: points awarded for products with published EPDs from at least five different manufacturers. | Published EPD directly qualifies for MR EPD credit. Lifecycle analysis demonstrates reduced environmental impact. |
| PAS 2080 | Carbon management in infrastructure: requires whole-life carbon assessment using verified data. Infrastructure clients (Network Rail, water companies, highways) increasingly require PAS 2080 compliance. | EPD provides the verified A1–A3 data required for PAS 2080 whole-life carbon calculations. |
Pultruded profiles are approximately 20% stronger in flexural strength and twice as stiff as moulded equivalents. For structural applications, handrails, platforms, stairs, and framing — pultrusion is the correct choice. Moulded grating has its place for shorter-span flooring where bi-directional loading and impact resistance are priorities.
10. The Buyer’s Checklist: 10 Questions on Carbon and Lifecycle
| # | Question | Good Answer | Red Flag |
| 1 | Can you provide an Environmental Product Declaration? | Published EPD available | ‘We’re working on it’ |
| 2 | What standard is the EPD produced to? | EN 15804+A2 / ISO 14040 | No standard cited |
| 3 | What is the GWP per kg (A1–A3)? | Specific number stated | ‘Low carbon’ with no data |
| 4 | Is the comparison on a functional unit basis? | Yes — adjusted for weight | Per-kg only |
| 5 | Does the comparison include maintenance carbon (B2)? | Yes — full lifecycle | A1–A3 only |
| 6 | Does the comparison include replacement carbon (B4)? | Yes — service life stated | Not considered |
| 7 | What is the declared design life? | 50+ years with evidence | Undefined |
| 8 | Are the assumptions stated transparently? | Environment, maintenance, life | No assumptions shown |
| 9 | Has the EPD been third-party verified? | Verified by accredited body | Self-declared only |
| 10 | Can you provide a project-specific carbon calculation? | Yes — bespoke to your project | ‘Use the generic data’ |
11. The Bottom Line
The carbon conversation is no longer a nice-to-have. It is a contractual requirement on most major UK infrastructure projects, a scoring criterion under BREEAM and LEED, and increasingly a deciding factor in material specification.
GRP’s carbon story is strong, but only if it is told correctly. On a per-kilogram basis, GRP has a higher embodied carbon than steel. On a functional unit basis — adjusting for the 75–80% weight saving — GRP delivers 70% lower embodied carbon. When the full lifecycle is included — zero maintenance, no replacement, longer design life — GRP delivers up to 67.5% lower whole-life carbon even after accounting for steel’s recycling credit.
The numbers are real. They are independently derived. They are available in our published EPD. And they are ready to be applied to your next project.
