Building Your First Model

Now that you have openLCA installed and databases imported, it's time to build an actual LCA model. In this lesson, we'll create a complete product system for a simple product, connecting processes to form a full supply chain.

The Modeling Workflow

Building an LCA in openLCA follows these steps:

1. Define your product and functional unit
2. Create or find processes for each life cycle stage
3. Link processes into a product system
4. Calculate results using LCIA methods
5. Analyze and interpret the outcomes

Let's work through each step with a concrete example: a simple ceramic coffee mug.

Step 1: Define Your Product

Before touching the software, clearly define what you're assessing:

Product: Ceramic coffee mug Functional unit: One mug providing 3 years of daily use (approximately 1,000 uses) System boundary: Cradle-to-grave including raw materials, manufacturing, use phase, and end-of-life

This scope determines which processes we need to model.

Step 2: Create Your Foreground Process

While databases provide background data, you'll often need to create "foreground" processes specific to your product.

Creating a New Process

1. In the Navigation panel, expand your database
2. Right-click on Processes
3. Select New process
4. Enter a name: "Ceramic mug production"
5. Click Finish

Configuring the Process

The process editor opens with several tabs:

General information:

• Name: Ceramic mug production
• Description: Manufacturing of a 350g ceramic coffee mug
• Category: Create or select an appropriate category

Inputs/Outputs tab: This is where you define what goes in and out of your process.

Adding the Reference Product

Every process needs a reference product—the main output:

1. Go to the Inputs/Outputs tab
2. In the Outputs section, click Add
3. For Flow, click the browse button and select New flow
4. Create a product flow named "ceramic mug"
5. Set the Amount to 1
6. Set the Unit to "Item(s)" or "p" (pieces)
7. Check the Reference box—this marks it as the process's main output

Adding Material Inputs

Now add the inputs needed to make the mug:

1. In the Inputs section, click Add
2. Search for "clay" or "ceramic" in your database
3. Select an appropriate process (e.g., "clay preparation" or "ceramic raw material")
4. Enter the amount: 0.35 kg (the mug's weight)

Continue adding inputs:

Adding Direct Emissions

For emissions from your process (not upstream), add elementary flows:

1. In Outputs, click Add
2. Search in Elementary flows (not processes)
3. Add "Carbon dioxide, fossil" to air: 0.15 kg
4. Add "Water vapor" to air: 0.8 kg

Handling Uncertainty (Optional)

For more robust analysis, add uncertainty to key values:

1. Click on an input amount
2. In the properties, find Uncertainty
3. Select a distribution type (e.g., Normal, Lognormal)
4. Enter the standard deviation or geometric standard deviation

Step 3: Add Life Cycle Stages

A complete LCA needs multiple stages. Let's add use phase and end-of-life:

Use Phase Process

Create a new process: "Ceramic mug use phase"

Inputs:

• Ceramic mug: 1 item (link to your production process)
• Tap water (for washing): 2,000 L (1,000 uses × 2L per wash)
• Dishwasher electricity: 50 kWh (estimate for 1,000 cycles, partial load allocation)

Outputs:

• Ceramic mug (used): 1 item
• Wastewater: 2,000 L (to elementary flows)

End-of-Life Process

Create a new process: "Ceramic mug end-of-life"

Inputs:

• Ceramic mug (used): 1 item

Outputs:

• Inert waste to landfill: 0.35 kg (elementary flow)
• Transport: Include transport to disposal if desired

Step 4: Create a Product System

Product systems link processes together for calculation. They represent the complete supply chain.

Building the Product System

1. Right-click on your main process ("Ceramic mug use phase" for a cradle-to-grave scope)
2. Select Create product system
3. In the dialog:
   • Name: Ceramic mug life cycle
   • Target amount: 1 item
   • Auto-link: Select By provider (recommended)
4. Click Finish

Understanding Auto-linking

Auto-linking connects your foreground processes to background database processes. The options:

• By provider: Connects to the default provider for each flow
• By product: Matches by product flow name
• Cutoff: Leaves flows unlinked (manual linking required)

Viewing the Model Graph

After creation, view the supply chain visually:

1. Open your product system
2. Go to the Model graph tab
3. You'll see processes as boxes with connections showing material/energy flows

Use the toolbar to:

• Zoom in/out
• Rearrange nodes
• Expand/collapse supply chains
• Export the graph as an image

Manual Linking

If auto-linking missed connections or linked incorrectly:

1. Go to the Linking tab
2. Find unlinked flows (marked with warnings)
3. Click on a flow and select the correct provider process
4. For multi-option flows, choose the most appropriate provider

Step 5: Configure Calculation Settings

Before calculating, review system settings:

Allocation Method

If any processes have multiple products:

1. Open the product system settings
2. Select an allocation method (Physical, Economic, or None)
3. Ensure this matches your goal and scope

Cut-off Rules

Decide how to handle small flows:

1. In product system settings, find cut-off options
2. Consider excluding flows below a threshold (e.g., 1% of total)
3. Document what's excluded

Step 6: Run the Calculation

Now calculate impacts:

1. With your product system open, click Calculate in the toolbar
2. Select calculation type:
   • Quick result: Fast, basic results
   • Analysis: Full contribution analysis
   • Monte Carlo: For uncertainty analysis
3. Select an LCIA method (e.g., ReCiPe 2016 Midpoint)
4. Click Finish

Understanding Results

The calculation opens several views:

Impact analysis:

• Shows total impact for each category
• Click on a category to see contributing processes

Inventory results:

• Lists all elementary flows in the system
• Useful for detailed emissions tracking

Contribution tree:

• Hierarchical breakdown of where impacts come from
• Expand nodes to trace impacts to specific processes

Sankey diagram:

• Visual flow diagram sized by contribution
• Intuitive way to spot hotspots

Validating Your Model

Before trusting results, validate your model:

Sanity Checks

1. Order of magnitude: Are results reasonable compared to literature?
2. Mass balance: Do material inputs roughly equal outputs?
3. Dominant contributors: Do hotspots make sense?

Common Issues

Zero results: Check that all processes are linked and have the correct reference product.

Unexpectedly high impacts: Look for unit mismatches (kg vs. ton, kWh vs. MJ).

Missing contributions: Verify flows are mapped to LCIA methods.

Saving and Exporting

Save Your Work

openLCA auto-saves to the database, but you can also:

• Export processes as JSON-LD for sharing
• Create database backups regularly

Export Results

1. Go to File → Export
2. Choose format (Excel, JSON, HTML report)
3. Select what to include
4. Save to your desired location

Key Takeaways

1. Every process needs a reference product and quantified inputs/outputs
2. Link foreground processes to database background data
3. Product systems represent the complete supply chain for calculation
4. Auto-linking speeds setup but may require manual corrections
5. Validate results before drawing conclusions

Practice Exercise

Extend the coffee mug model:

1. Add packaging (cardboard box) to the production stage
2. Add retail transport from factory to store
3. Compare impacts with and without packaging

How much does packaging contribute to the total Global Warming Potential?

What's Next?

With your model built, the next lesson covers running different types of impact assessments and exporting results for reporting.

---

Resources

• openLCA Modeling Guide
• openLCA Community Forum