What is the Life Cycle Inventory (LCI) and how is it used

The Life Cycle Inventory (LCI) is the complete, quantified list of every flow of materials, energy, water, emissions, and waste that enters and leaves a product system, from raw material extraction to end of life. It is the second phase of a Life Cycle Assessment (LCA) and, in practice, the one that most determines its quality: without a rigorous inventory, the results lose credibility with regulators, customers, and investors.

This article explains what information an LCI contains, why it is key to corporate sustainability, and how to build it step by step.

If you want to review the LCA as a whole, you can read the article Life Cycle Assessment: how to evaluate a product's environmental impact and the guide to methods and tools for the LCA.

What information does an LCI contain?

An LCI gathers, in verifiable units, the quantities of raw material, the electricity consumed, the water used, and the kilograms of emissions or waste involved in each life cycle stage: extraction, processing, distribution, use, and end of life. That traceability is what makes it possible to turn sustainability claims into auditable metrics.

The Life Cycle Inventory combines two types of data: primary data, measured directly at the plant or process, and secondary data, drawn from recognised databases such as Ecoinvent. The greater the weight of primary data in the relevant processes, the more robust the inventory.

Why is the LCI key to corporate sustainability?

A well-built and, where appropriate, verified LCI reduces uncertainty in measuring the carbon footprint and the water footprint, which increases the trust of investors and customers. It is also the basis on which environmental declarations are built: without a traceable inventory it is not possible to issue a credible Environmental Product Declaration (EPD) or product carbon footprint.

In addition, a solid inventory makes it easier to pass sustainability audits and investor due diligence processes and disclosure frameworks such as CDP, because it provides the detail and traceability they require.

Steps to build a robust Life Cycle Inventory

1. Define scope and functional unit

Choose the system boundaries (for example, cradle to grave) and the functional unit, such as one litre of paint. A flow diagram validated by management helps avoid gaps and overlaps.

2. Map processes and sub-processes

Draw a schematic with the system nodes (for example, injection, drying, and packaging) that then link to meter readings and process sheets.

3. Collect primary data

Extract information from flowmeters, energy meters, and plant control systems. It is advisable to check consistency with a mass and energy balance between inputs and outputs.

4. Complete with quality secondary data

For stages without direct measurement, recognised databases are used, always documenting their origin. An EPD requires a relevant share of primary data in the main processes.

5. Verify balances and document assumptions

Every assumption is recorded for the later critical review under ISO 14044, which is the standard that sets the inventory requirements.

How to turn the LCI into a competitive advantage

The LCI makes it possible to locate the critical points or hot spots where most of the environmental impact is concentrated, which helps prioritise improvement actions. It also makes it possible to quantify the effect of eco-design, such as reducing the weight of packaging, which translates into a direct reduction of the associated emissions.

A traceable inventory also strengthens the company's position in commercial negotiations, because it makes it possible to demonstrate environmental advantages over competitors with data rather than generic claims.

Lead your sustainability strategy with data

The Life Cycle Inventory turns green promises into verifiable metrics. Integrating it into the sustainability roadmap makes it possible to justify investments and differentiate the brand with evidence. Platforms such as Manglai's product footprint help structure the inventory and connect it with the corporate water footprint and with sustainability reporting.

Frequently asked questions about the Life Cycle Inventory (LCI)

What is the difference between primary and secondary data?

Primary data are measured directly at the plant; secondary data come from recognised databases. An Environmental Product Declaration requires a relevant share of primary data in the main processes.

How long does it take to compile an LCI?

It depends on the complexity of the system. A simple product may require a few weeks, while a complex system, such as a complete vehicle, may take several months.

Is specialised software needed?

For rigorous results, yes. Tools such as OpenLCA or SimaPro reduce errors and provide full traceability.

How is the LCI related to the carbon footprint?

The product carbon footprint is calculated from the inventory, selecting the flows that contribute to climate change. The LCI is therefore the common starting point for any impact indicator.