If you’ve ever looked at an emission factor and wondered “Where does this number come from?” or “What method is being used here?”, this article is for you.

With the launch of ecoinvent v3.11, Variable now gives you access to more emission factors than ever — and we’re making it easier to understand how they’re calculated and what they mean for your results.

🔁 What’s a system model?

A system model defines how emissions are counted across a product’s life cycle — especially how recycled materials, waste, and co-products are treated.

For ecoinvent v3.11, Variable currently supports the Allocation, cut-off, EN15804+A2 system model. It’s based on the same core principles as the standard Allocation, cut-off by classification model:

• Recycled inputs are treated as burden-free, meaning no upstream emissions are assigned to them.

• Co-products are allocated based on physical properties (typically mass or energy content).

• The model is widely used for both product carbon footprint calculations and EPD generation.

The key difference is that the EN15804 version includes Module D, which reports the potential benefits of recycling or energy recovery after the product’s end of life. These benefits are only reported in EPD results — they do not affect PCF or carbon accounting values.

Using this model ensures that you can calculate both Product Carbon Footprints (PCFs) and EPDs with consistent, high-quality data. Variable also displays the system model used for each dataset, so you always know how your results are calculated.

Ecoinvent also offers other system models, such as:

• Consequential, which models long-term market effects and system-wide changes in supply and demand

• Allocation at the point of substitution, which assigns credits to co-products based on assumed substitution of other products in the market

These approaches are useful for policy studies and academic research, but they are not used for PCFs, EPDs, or carbon accounting. That’s why Variable focuses on the Allocation, cut-off, EN15804+A2 model, the most widely accepted and relevant for practical, real-world product assessments.

📏 What’s an LCIA method?

LCIA stands for Life Cycle Impact Assessment. It’s how we translate emissions data (like CO₂, CH₄, or N₂O) into environmental impacts — such as climate change, acidification, or water pollution.

At Variable, we focus on methods that are widely used and recognized:

• IPCC GWP

  This refers to Global Warming Potential over 100 years (GWP100), based on IPCC reports. It’s the standard metric for climate impact in the GHG Protocol, ISO 14067, PAS 2050, and most PCF frameworks .

  → This is Variable’s default for carbon footprint calculations.

  
  

• EN 15804+A2

  Used for Environmental Product Declarations (EPDs). It requires 19 specific impact categories and defines consistent modeling rules for construction products in particular.

📊 What impact indicators are included?

By default, Variable focuses on fossil-based Global Warming Potential (GWP) — the most relevant and widely reported indicator for carbon accounting, LCAs, and PCFs.

ecoinvent v3.11 also includes additional indicators, such as:

• 🌿 Biogenic GWP

• 💧 Eutrophication

• ☁️ Acidification

• 🧂 Resource depletion

• ...and others required under EN 15804+A2

These additional indicators will be available in Variable soon as part of an upcoming release of the extended LCA functionality with support for EPDs — so you’ll be able to calculate the full environmental profile for all your products.