3. EPD vs Carbon Footprint vs LCA: What’s the Difference?

Environmental assessment terminology confuses people because the terms overlap. Life Cycle Assessment, carbon footprint, and Environmental Product Declaration all involve quantifying environmental impacts, but they’re different things used for different purposes. Understanding what distinguishes them helps you choose the right approach for your needs.

The confusion is understandable. All three involve collecting data about materials, energy, transport, and processes. All three produce numbers describing environmental impacts. All three reference similar standards. Yet they differ fundamentally in scope, requirements, and intended use.

Life Cycle Assessment: The Foundation Methodology#

Life Cycle Assessment (LCA) is the underlying methodology for quantifying environmental impacts across a product’s life cycle. It’s governed by ISO 14040 and ISO 14044, which define how to conduct LCA studies regardless of what you intend to do with the results.

LCA follows four phases. Goal and scope definition establishes what you’re studying and why. Life cycle inventory analysis compiles the inputs and outputs (materials, energy, emissions, waste). Impact assessment calculates environmental impacts from the inventory data. Interpretation evaluates results and draws conclusions.

The critical feature of LCA is comprehensiveness. You trace impacts from raw material extraction through manufacturing, use, and disposal. You account for energy, transport, auxiliary materials, and waste treatment. You calculate multiple impact categories: climate change, acidification, eutrophication, resource depletion, water consumption, and others.

LCA is flexible. You define system boundaries appropriate for your study. You choose impact categories relevant to your questions. You determine data quality requirements. You decide whether to include optional life cycle stages. This flexibility makes LCA applicable to diverse questions but it also means LCA studies aren’t automatically comparable.

Two LCA studies of the same product might reach different conclusions because they made different methodological choices. One might use European databases while another uses global averages. One might include end-of-life while another stops at factory gate. One might assess 15 impact categories while another focuses on five.

LCA exists primarily as an internal decision support tool. Companies use LCA to compare design alternatives, identify improvement opportunities, or understand their products’ environmental profiles. The ISO 14040 series doesn’t mandate public disclosure or verification. You can conduct LCA, use the results internally, and never publish anything.

This internal focus distinguishes LCA from carbon footprints and EPDs, which are communication tools.

Carbon Footprint: LCA Focused on Climate#

A product carbon footprint quantifies greenhouse gas emissions across the life cycle, expressed as carbon dioxide equivalents (CO₂e). It’s essentially LCA restricted to one impact category: climate change.

ISO 14067 governs carbon footprinting. The standard builds on ISO 14040/44 but adds specific requirements for GHG quantification, biogenic carbon accounting, and communication.

Carbon footprints are simpler than full LCA because you track only emissions relevant to climate change. You don’t calculate acidification, eutrophication, or toxicity. You don’t assess resource depletion or water consumption. This focus makes carbon footprinting faster and cheaper than comprehensive LCA.

The simplification has appeal. Climate change dominates environmental policy and public attention. Customers understand CO₂e. Regulations focus on carbon. For many purposes, knowing the carbon footprint provides adequate information without the complexity of full LCA.

Carbon footprints serve both internal and external purposes. Internally, companies use them to identify emission hotspots and track reduction progress. Externally, they communicate climate performance to customers, investors, or regulators.

Here’s where verification becomes critical. ISO 14067 makes verification optional. You can calculate a carbon footprint, claim conformance with ISO 14067, and never have anyone check your work. Some companies choose verification for credibility. Others don’t.

This creates a credibility spectrum. Unverified self-declared carbon footprints have unknown reliability. Verified carbon footprints with detailed review reports carry more weight. But even verified carbon footprints face comparability challenges because companies choose different system boundaries, allocation methods, and data sources within ISO 14067’s flexibility.

EPD: Standardised LCA Communication#

An Environmental Product Declaration is a communication format for presenting LCA results in a standardised, verified, comparable way. EPDs don’t replace LCA. They’re based on LCA conducted according to ISO 14040/44, then packaged according to ISO 14025 requirements.

The distinguishing features of EPDs are standardisation and verification.

Standardisation comes through Product Category Rules (PCRs) that specify exactly how to conduct LCA for a product category. The PCR defines functional unit, system boundaries, required life cycle stages, mandatory impact categories, data quality requirements, and allocation rules. Every EPD in a category follows the same PCR, making comparison meaningful.

This removes the flexibility that makes LCA studies incomparable. You can’t choose which life cycle stages to include. You can’t select impact categories based on favourable results. You can’t define system boundaries to exclude inconvenient processes. The PCR dictates methodology.

Verification is mandatory. An independent verifier checks that the LCA follows the PCR and ISO 14040/44, that data meets quality requirements, and that the EPD accurately presents results. This verification isn’t optional like ISO 14067. It’s required by ISO 14025, with most programme operators mandating third-party verification even when the standard would permit independent internal verification.

EPDs report multiple impact categories. Construction product EPDs following EN 15804 must report at minimum seven core environmental impacts plus additional indicators. You can’t create an EPD that reports only carbon and ignores other impacts.

EPDs organise results into life cycle modules (A1-A3, B1-B7, C1-C4, D) providing detailed transparency about where impacts occur. This modular structure supports building-level assessment and product comparison in context.

EPDs exist as public documents registered with programme operators. They’re communication tools, not internal studies. Creating an EPD means making detailed environmental data publicly available.

The Relationship Between Them#

These three aren’t alternatives. They’re related tools with different applications.

LCA is the foundation. Both carbon footprints and EPDs require LCA. You can’t create either without conducting underlying LCA according to ISO 14040/44.

Carbon footprints are focused LCA. You conduct LCA limited to climate change impacts, follow ISO 14067 requirements for GHG accounting, and optionally verify results. The carbon footprint might be based on the same inventory data as an EPD but reports only the climate change impact.

EPDs are comprehensive LCA packaged for standardised communication. You conduct full LCA following both ISO 14040/44 and the relevant PCR, assess multiple impact categories, undergo mandatory verification, and publish results in standardised format.

You might conduct LCA that generates both carbon footprint and EPD. The LCA provides complete inventory data. You extract climate change impacts to report a carbon footprint. You assess all required impact categories to create an EPD. Same underlying data, different communication formats serving different needs.

When to Use Each Approach#

Choose LCA when:

• You need detailed understanding for internal decisions
• You’re comparing design alternatives
• You want to identify improvement opportunities
• You don’t need to communicate results externally
• You need flexibility in scope and method

LCA supports product development, process optimisation, and strategic planning. It’s the tool for understanding your environmental profile and finding reduction opportunities. You control the study scope and keep results internal.

Choose carbon footprint when:

• Climate change is the priority impact
• Customers or regulations require carbon data specifically
• You need quick, cost-effective assessment
• Full multi-impact LCA is unnecessary
• You want flexibility in verification

Carbon footprints suit corporate carbon accounting, customer carbon data requests, and climate-focused decision making. They’re faster and cheaper than EPDs because they assess only one impact category and don’t require PCR compliance or mandatory verification.

Choose EPD when:

• Regulations require EPDs specifically
• You need green building certification credits
• Customers specify EPD requirements
• You want credible competitive differentiation
• Product comparison in standardised format matters

EPDs suit regulated markets, green building supply chains, and situations demanding verified multi-impact assessment. They cost more and take longer than carbon footprints but they deliver higher credibility and broader impact coverage.

The Verification Difference#

Verification requirements fundamentally distinguish these approaches.

LCA studies (ISO 14040/44) don’t require verification at all. You can conduct LCA, use results internally, and never have anyone check your work. If you choose critical review, you decide the scope and who conducts it. The standards don’t mandate external oversight for conformance.

Carbon footprints (ISO 14067) make verification optional. You can claim conformance whether verified or not. Some companies pursue verification for credibility. Others don’t. The standard doesn’t distinguish verified from unverified footprints in terms of conformance.

This creates a credibility problem. Two products both claim carbon footprints conforming to ISO 14067. One underwent rigorous third-party verification. One was self-declared with no external review. Both technically conform to the standard. Users can’t tell which is which unless verification status is disclosed.

EPDs (ISO 14025) require mandatory verification. The standard specifies independent verification as minimum, with third-party verification required for consumer-facing declarations. Most programme operators mandate third-party verification even for business-to-business EPDs. You cannot create a conformant EPD without verification.

This verification requirement gives EPDs inherently higher credibility than optional-verification carbon footprints. When someone presents an EPD, you know it underwent independent review. When someone presents a carbon footprint, verification status remains uncertain unless explicitly stated.

The Comparability Challenge#

All three approaches face comparability challenges but to different degrees.

LCA studies are highly flexible. Two studies of identical products might use different databases, impact methods, system boundaries, and allocation rules. They could reach contradictory conclusions, both validly conducted according to ISO 14040/44. Direct comparison requires checking that methodologies align.

Carbon footprints constrain some choices through ISO 14067 requirements but substantial flexibility remains. System boundaries, biogenic carbon treatment, allocation methods, and data sources vary between footprints. Companies might choose boundaries that present their product favourably. Comparison requires methodological alignment checking.

EPDs maximise comparability through PCRs that eliminate flexibility. Every EPD in a category follows identical methodology. System boundaries, impact methods, and data quality requirements are specified. Comparability is built in, though comparing EPDs still requires checking they follow compatible PCRs from compatible programmes.

The tradeoff is clear. LCA flexibility supports diverse applications but prevents comparison. EPD standardisation enables comparison but constrains methodology. Carbon footprints sit in the middle with partial standardisation.

Cost and Timeline Differences#

Resource requirements vary substantially.

LCA studies depend entirely on scope. A screening LCA with generic data might take weeks. A detailed LCA with primary data collection could take months. Costs range from several thousand pounds to tens of thousands depending on product complexity, data availability, and required detail. No verification costs if results stay internal.

Carbon footprints are generally cheaper than full LCA because they assess one impact category. Data collection requirements are similar but impact assessment is simpler. Timeline might be weeks to months depending on supply chain complexity. Verification adds cost if pursued, typically several thousand pounds for third-party review.

EPDs are the most expensive and time-consuming option. You need full LCA covering all required impact categories, PCR compliance checking, programme operator fees, and mandatory verification. Costs and timelines typically run several thousand to twenty thousand pounds and three to six months for first-time EPDs. Updates are faster and cheaper.

The cost difference reflects the different purposes. LCA is an internal tool with flexible scope. Carbon footprints provide focused communication. EPDs deliver comprehensive, verified, standardised transparency.

Can You Have Multiple?#

Yes, and many companies do. The three serve different needs.

You might conduct comprehensive LCA for internal decision support, extract climate data to report a carbon footprint satisfying customer requirements, and create an EPD for green building market access. Same product, same underlying data, multiple communication formats.

The efficient approach is conducting thorough LCA that meets EPD data requirements. This generates inventory data supporting all three outputs. You can produce internal LCA reports for decision making, carbon footprint communications for customers requesting climate data specifically, and EPD for markets requiring standardised declarations.

Trying to retrofit an EPD from a limited carbon footprint study often fails because the carbon footprint may lack data for other impact categories or may not follow PCR system boundary requirements. Starting with EPD-level data collection enables multiple outputs. Starting with minimal carbon footprint data limits options.

Making the Choice#

Select based on your needs, requirements, and audience.

If regulations or customers explicitly require EPDs, you need EPDs. Carbon footprints or LCA studies won’t satisfy those requirements. Check whether your business needs an EPD based on your markets and customers.

If climate data is sufficient and no one requires broader assessment, carbon footprints may be adequate. They’re faster and cheaper than EPDs while providing climate information.

If you need environmental understanding for internal improvement without external communication, LCA without public disclosure suits your needs. You maintain flexibility and control.

Consider the credibility level you need. Self-declared carbon footprints have limited credibility. Verified carbon footprints carry more weight. EPDs with mandatory verification and standardised methodology provide highest credibility for product claims.

Think about comparability requirements. If enabling direct product comparison matters, EPDs provide the standardisation needed. If you’re just reporting your absolute performance without comparison, carbon footprints or LCA suffice.

The Standards Foundation#

All three build on ISO 14040 and 14044 for LCA methodology. Understanding that foundation helps you see how they relate:

• ISO 14040/44: LCA methodology applicable to all three approaches
• ISO 14067: Carbon footprinting specifics built on ISO 14040/44
• ISO 14025: EPD programme and declaration requirements built on ISO 14040/44
• EN 15804: Construction product EPD specifics built on ISO 14025

The standards form a hierarchy. ISO 14040/44 provides methodology foundation. ISO 14067 and ISO 14025 add specific requirements for communication formats. EN 15804 adds sector-specific rules for construction.

Starting Your Assessment Journey#

Whether you pursue LCA, carbon footprint, or EPD, you need similar foundational work:

• Product definition and functional unit
• System boundary determination
• Data collection from manufacturing and supply chain
• Database selection for background processes
• Impact assessment method selection

This common foundation means starting with one approach doesn’t prevent pursuing others later. Building robust data collection systems and supply chain engagement supports all three outputs.

For most manufacturers entering environmental assessment, the progression often follows: preliminary LCA for internal understanding, carbon footprint for customer communication if requested, EPD if regulations or markets require it. Each step builds on previous work.

The key is understanding what each tool does and matching that to your needs rather than pursuing the most comprehensive option by default. LCA, carbon footprints, and EPDs all have roles. Choosing the right tool for your context makes environmental assessment productive rather than just another compliance burden.