Life Cycle Assessment (LCA) is a methodology for quantifying the potential environmental impacts of a product or system across its life cycle—from upstream materials and processing through use and end-of-life. In practice, an LCA is a structured model of a real supply chain that helps you understand where impacts come from, what drives them, and what changes will matter most.

What questions does LCA help answer?

LCA helps answer practical questions like:

• What is the environmental impact of 1 L of my favourite Dairy Milk? How does it compare to Oat Milk? Almond Milk?

• Are greenhouse gas emissions saved when I buy tomatoes from the farmer's market? Versus from international growers?

• What is the lifetime impact of electric vehicles vs. fossil-fuel based vehicles? What opportunities are there to reduce this?

LCA results are used by businesses, investors, consumers, and policymakers to evaluate environmental (and often economic and social) trade-offs and to guide decisions with more confidence and transparency.

Sustainability decisions are rarely simple. Changes that reduce emissions in one area can increase impacts elsewhere, and “green” claims often depend on boundary choices, assumptions, and data quality.

LCA is designed for this reality. It provides a consistent way to:

• define what you’re measuring,

• track impacts across the full system, and

• compare options using a shared basis (your unit of analysis).

How are LCAs utilized across society?

• The Public - LCAs support more informed choices by making impacts clearer and more comparable.

• Enterprise - LCAs guide product strategy and operational improvements by revealing impact hotspots.

• Supply Chain Managers - LCAs help prioritize supplier engagement and procurement decisions using measured drivers of impact.

• Brand Managers - LCAs provide a credible foundation for environmental communications grounded in traceable data.

• Retailers - LCAs support product selection and category strategy as customer and regulatory expectations evolve.

Overall, LCAs help teams move from intuition and marketing claims to structured, evidence-based decisions—and they provide the transparency needed to build trust with customers, partners, and regulators.

At CarbonGraph, we like to think of an LCA as a living model of a supply chain: a digital representation of activities and exchanges that can be refined as better data becomes available. You don’t “do an LCA once”—you build a model that can evolve as inputs change, suppliers shift, assumptions are revisited, and uncertainty is reduced.

Practically, practitioners move through the steps iteratively. The process has a clear structure, but real-world modeling is rarely linear.

The Five Steps in LCA

The LCA process is typically broken into five steps:

• Step 1: Goal and scope definition

• Step 2: Data Collection, Allocation, & Handling Uncertainty

• Step 3: Building the Life cycle Inventory (LCI)

• Step 4: Life cycle Impact assessment (LCIA)

• Step 5: Interpretation of Results & Reporting

You’ll see these steps recur across standards and guidance.

Links to External Methodology Resources

• ISO 14040 - Life cycle assessment Principles and framework — https://www.iso.org/standard/37456.html

• ISO 14044 - Life Cycle Assessment Requirements and Guidelines — https://www.iso.org/standard/38498.html

• ISO 14067 - Greenhouse gases Carbon footprint of products — https://www.iso.org/standard/71206.html

• ISO 14025 - Environmental labels and declarations — https://www.iso.org/standard/38131.html

• GHG Protocol - Product Life Cycle Accounting and Reporting Standard — https://ghgprotocol.org/sites/default/files/standards/Product-Life-Cycle-Accounting-Reporting-Standard_041613.pdf

• U.S. General Services Administration - Life Cycle Assessment Overview — https://sftool.gov/plan/400/life-cycle-assessment

• Attributional and Consequential Life Cycle Assessment — https://www.intechopen.com/chapters/69212

This step sets the foundation for everything that follows. A strong goal and scope makes results easier to interpret, easier to explain, and harder to misread.

At a high level, LCAs are often used to support goals like:

Change Management

Use LCA to understand where impacts are generated across the supply chain, then focus improvements where they’ll matter most. This is especially valuable when regulations are evolving or when impact drivers are distributed across many suppliers and processes.

Performance Tracking

An LCA model can be revisited as your product, sourcing, or operations change. That allows you to measure progress over time—using the same structure and assumptions—so that improvements are comparable and traceable.

Stakeholder Stewardship

LCAs provide a shared language for environmental performance. They help you collaborate with suppliers and partners, communicate constraints and trade-offs clearly, and build trust through transparent methods and documented assumptions.

Product Differentiation

When environmental performance is backed by traceable modeling and credible reporting, it becomes a real differentiator. LCA helps teams make claims that are grounded in method and data—not vibes.

Defining the Scope & Boundary Limits of the Product's Life Cycle

To establish the study’s framework, define:

• Boundary Limits — what life cycle stages are included

• Unit of Analysis — what quantity/function you’re reporting results for (functional or declared unit)

What are the Boundary Limits of an LCA?

Boundary limits determine which stages are included or excluded. Common boundary types include:

• Cradle-to-Grave: Full life cycle from extraction through end-of-life. Most comprehensive view.

• Cradle-to-Gate: From extraction through manufacturing, ending when the product leaves the factory. Common for material and intermediate products.

• Gate-to-Gate: A focused segment of the supply chain, often within a single facility or process step.

• Gate-to-Grave: From factory exit through use and end-of-life. Useful when the production stage is not being assessed.

Each choice changes what your results represent—and what conclusions you can (and can’t) draw.

What is the Unit of Analysis of an LCA?

The unit of analysis determines what “one unit” means for your results.

• Functional Unit: Tied to what the product does, especially important for comparing alternatives that provide the same function. It typically includes:

  • Magnitude (quantity/size)

  • Useful duration (lifespan/number of uses)

  • Quality parameters (performance specs)

  Example: “The LCA was conducted for a 500 ml steel meal container with a silicone lid, designed for 1,000 reuses.”

• Declared Unit: A simpler unit based on physical quantity (mass/volume/count), often used when comparability is not the primary goal.

  Example: “1 tonne of 68% Fe Ore.”

• Unit of Analysis: The amount of product/service the results are based on, derived from either the functional or declared unit.

Starting to Map the Supply Chain

Once goal and scope are set, the next step is to map the system you’re modeling. Think of this as establishing the structure your data will attach to.

A Product Life Cycle Map is a visual representation of stages, activities, and flows across the system boundary.

What is a Product Life Cycle Map?

A Product Life Cycle Map captures the stages of a product’s journey, from upstream materials to end-of-life processing. It helps you understand how activities connect, where key inputs and outputs occur, and where impacts are likely to concentrate.

By laying out the structure, the map helps you identify key exchanges and avoid leaving out important stages.

How do I create a Product Life Cycle Map?

• Identify stages across the life cycle (materials, production, distribution, use, end-of-life)

• Define boundaries clearly (cradle-to-gate, cradle-to-grave, etc.)

• Track inputs/outputs (materials, energy, emissions) at each stage

• Visualize interactions between stages so the system structure is explicit

CarbonGraph’s modeling interface is designed to support building—and evolving—these maps over time.

Once the structure is defined, you start attaching data to the model. This is where real-world constraints show up: missing data, inconsistent units, supplier variability, and uncertainty.

The quality of your inputs determines the quality of your results—so a key part of this step is being explicit about data quality and gaps.

Why is tracking data quality important?

• Identify weak points where data is low-confidence or missing

• Assess uncertainty and understand how it influences results

• Communicate limitations clearly and traceably

• Improve over time by focusing collection on what actually matters

What sources of data can be utilized for the LCA?

Data typically comes from a mix of:

Primary Data Sources

Information collected from production steps within the ownership or control of the reporting company (e.g., measured material weights, facility electricity usage).

Secondary Data Sources

Information not directly measured for the study—such as LCA databases, industry averages, or spend-based estimates.

CarbonGraph also provides a comprehensive set of Reference LCA Data, which is readily accessible to all CarbonGraph users.

What data quality criteria should you consider?

• Technological quality: does it match the actual technology used?

• Geographical quality: does it match the region/location?

• Temporal quality: does it match the relevant timeframe/age?

• Completeness: are key inputs/outputs missing?

• Reliability: how dependable are sources and methods?

What other data collection challenges are there?

How do I handle uncertainty & fill data gaps?

Data gaps are normal. Primary or secondary data may not be available for certain steps due to confidentiality, limited resources, or poor availability by process or region. Best practice is to document and disclose these gaps—then prioritize improvements where they affect results most.

How do I model & allocate across multiple co-products?

Some production steps generate multiple valuable products, and the shared impacts must be attributed across outputs.

Example: a fish processing facility produces “fish fillets” and “fish by-products” (bones, oils, etc.). What fraction of the facility’s impacts should be associated with each?

LCA addresses this through allocation.

What are the allocation best practices?

• Process Subdivision — Split the process into sub-processes

• Functional Unit Redefinition — Combine outputs into a single unit (e.g., egg white + yolk = whole egg)

• System Expansion — Model downstream impacts for one co-product

• Physical Allocation — Allocate by mass/count/other physical relationships

• Economic Allocation — Allocate by market value

• Other Relationships Allocation — Allocate using a justified causal relationship

How do I model the use of recycled materials?

Recycling often spans multiple product life cycles, so allocation is required.

CarbonGraph recommends the Recycled Content Method (also known as the Cut-Off Method). This approach attributes recycling impacts to products that use recycled material upstream, and does not assign additional impacts to the end-of-life recycling stage of the product being assessed.

The Life Cycle Inventory (LCI) is the structured list of inputs and outputs for each production step in your model. If the life cycle map is your blueprint, the LCI is the bill of materials and exchanges that make it real.

A useful way to think about LCIs is as “recipes” for production activities. They can be detailed or high-level depending on what you need the model to represent.

Examples:

• 200g Flour + 100g Water + 5g yeast + 30 min in the Oven = ~200g of Bread

• 2 units of Laces + 2 units of Unlaced Shoes = 1 pair of Laced Shoes

• 500 kWh of Electricity + 1 tonne Scrap Metal = 1 tonne of Liquid Steel

Each input and output is an exchange. Exchanges typically fall into two categories: Elementary and Product Exchanges.

What are Elementary Exchanges?

Elementary exchanges are direct flows between the economy and the environment: resources extracted from nature and emissions/waste released back to nature.

Examples: 1 kg of CO₂ emitted to air, or 1000 kg of iron ore extracted.

What are Product Exchanges?

Product exchanges are human-made materials/services exchanged between production steps within the economy (sometimes described as the “technosphere” or “market”).

Examples: butter, grapes, steel plate—processed goods transferred between stages.

How do LCIs of individual activities become a complete LCA?

A full supply chain model is built by connecting LCIs across production steps. The “right” structure depends on the life cycle map created during goal and scope.

CarbonGraph’s LCA editing interface supports this structure with unit conversions and easy linking between LCIs, enabling complex supply chain models.

Example LCI in the CarbonGraph Platform

The LCI format in CarbonGraph supports advanced modeling (carbon sequestration, biogenic/non-biogenic emissions, carbon uptake, and more). Those topics are beyond the scope of this intro guide, but they become important in more advanced studies.

How do to model Carbon Offsets or Avoided Emissions?

Carbon offsets and avoided emissions are often used in climate strategies, but it’s important to separate them from the core inventory results.

According to ISO standards, offsets or avoided emissions cannot be directly subtracted from total inventory results. Instead, they may be reported separately as additional information, preserving transparency and comparability of the underlying LCA results.

In LCIA, inventory data is translated into impact results through a structured relationship between elementary flows, impact factors, impact categories, and characterization models.

Elementary Flows: The Building Blocks of Impact

Elementary flows are the direct exchanges with the environment—materials extracted and emissions released. They are the measurable quantities LCIA uses as inputs.

Impact Factors: Quantifying Environmental Impact

Each elementary flow has an associated impact factor per category—used to convert quantities into comparable impact units.

Example: 1 kg CO₂ emitted contributes 1 kg CO₂e in the Climate Change category.

Impact Categories: Grouping Related Environmental Impacts

Impact categories reflect environmental problems we want to assess, such as climate change or acidification.

Examples of LCIA Impact Categories

• Climate Change: potential contribution to global warming (CO₂e)

• Ozone Depletion: potential to deplete the ozone layer

• Acidification: potential to contribute to acid rain

• Resource Depletion: depletion of natural resources

Characterization Models: Frameworks for Impact Assessment

Characterization models define the methods and factors used to evaluate impacts across categories. Different models emphasize different categories and regional assumptions.

Examples of Characterization Models

• TRACI (Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts): North America-focused; developed by the U.S. EPA.

• ReCiPe: Global model; commonly used in Europe; supports midpoint and endpoint approaches.

• CML (Centrum voor Milieuwetenschappen Leiden): Midpoint-focused; strong European foundation.

• IMPACT 2002+: Integrates midpoints and endpoints.

• ILCD (International Reference Life Cycle Data System): EC guidance and recommended methods.

Calculation Methodology in LCIA

The calculation chain typically looks like:

How Does It All Connect?

• Elementary flows: raw environmental exchanges (e.g., 1 kg CO₂)

• Impact factors: coefficients translating flows into category impacts

• Impact categories: broader issues being assessed

• Characterization models: the framework that ensures consistent application

The Summarized LCIA Calculation Steps

• Inventory analysis: quantify elementary flows from the LCI

• Apply impact factors: convert flows into category results

• Aggregate across categories: summarize contributions per category

• Integrate (optional): combine categories or convert midpoints to endpoints (where applicable)

By understanding this chain, you can interpret what drives results—and what changes would reduce impacts most effectively.

The final step is interpreting results and communicating them responsibly. Good reporting provides context: what was modeled, what assumptions were made, what data was used, and what limitations exist.

This is also where you validate credibility by demonstrating adherence to core accounting principles: relevance, accuracy, completeness, consistency, and transparency.

Because LCAs serve many audiences, reporting should be tailored so the results are understandable and actionable.

Examples of Audiences for LCA Reports

• The Public: readers with little to no experience in LCA

• Policymakers: officials and regulators using results to inform decisions

• Sustainability Practitioners: technical audiences compiling and comparing studies

• External Stakeholders: customers, partners, and others evaluating products

Common LCA Report Contents

• Executive Summary: key findings and implications

• Recommendations for Action: decisions supported by results

• Visual Representation of Data: charts and diagrams that clarify findings

• Uncertainty Analysis: how assumptions and variability affect conclusions

• Comparative Analysis: benchmarking or comparison with prior work (when appropriate)

• Detailed Appendices: methodological notes and inventories for technical audiences

• Stakeholder Feedback: how engagement informed scope or interpretation

Example Disclaimer Text

“The results presented in this report are unique to the assumptions and practices of company X. The results are not meant as a platform for comparability to other companies and/or products. Even for similar products, differences in unit of analysis, use and end-of-life stage profiles, and data quality may produce incomparable results. The reader may refer to the additional resources for a glossary and additional insight into the LCA reporting process.”

CarbonGraph strives to create a flexible platform that can be used for any reporting framework.

Thank you for exploring our beginner's guide to Life Cycle Assessment (LCA). We hope this introduction has given you a practical foundation for understanding what LCA is, how it works, and why it’s useful.

For deeper insights into LCA methodology, explore these external resources:

• ISO 14040 - Life cycle assessment Principles and framework — https://www.iso.org/standard/37456.html

• ISO 14044 - Life Cycle Assessment Requirements and Guidelines — https://www.iso.org/standard/38498.html

• ISO 14067 - Greenhouse gases Carbon footprint of products — https://www.iso.org/standard/71206.html

• ISO 14025 - Environmental labels and declarations — https://www.iso.org/standard/38131.html

• GHG Protocol - Product Life Cycle Accounting and Reporting Standard — https://ghgprotocol.org/sites/default/files/standards/Product-Life-Cycle-Accounting-Reporting-Standard_041613.pdf

• U.S. General Services Administration - Life Cycle Assessment Overview — https://sftool.gov/plan/400/life-cycle-assessment

• Attributional and Consequential Life Cycle Assessment — https://www.intechopen.com/chapters/69212

If you have any questions, feedback, or suggestions, please don’t hesitate to contact us at support@carbongraph.io. Your insights are invaluable to us, and we’re always eager to improve our platform and resources to better serve your needs.