ave you ever wondered how environmental impacts are divided among products and by-products in a Life Cycle Assessment? Ecoinvent offers four distinct system models for this purpose, each with its own methodology and underlying philosophy. Whether you’re new to LCAs or a seasoned professional, understanding these approaches is key to transparent, meaningful sustainability assessments. Let’s explore each model with real-world examples.

1. Allocation, Cut-off by Classification
Imagine you run a bakery. Your signature loaves of bread are the key products, while the leftover dough scraps and crumbs are considered waste. In the “Allocation, Cut-off by Classification” model, the environmental burdens of primary production are assigned entirely to the main product—your bread. The wastes or recycled materials (the scraps) are “cut off” and treated separately. This means that, when these scraps are recycled (say, turned into animal feed or other products), they carry no legacy of the primary production processes. This method follows the “polluter pays” principle, ensuring that the burdens of waste treatment don’t unfairly fall on the primary product.

2. Allocation, Cut-off, EN15804
Tailored for the construction sector and aligned with the European standard EN15804, this model operates on the same cut-off principle but with specific guidelines for building products. Think about a façade panel manufacturer producing high-performance exterior panels. Under the “Allocation, Cut-off, EN15804” approach, any recycling inputs or production scraps aren’t burdened with impacts from the panel’s primary production processes. Instead, these flows are excluded based on standardized criteria, ensuring that environmental product declarations (EPDs) accurately reflect the building’s overall footprint in accordance with European norms.

3. Allocation at the Point of Substitution
Now, imagine an automotive manufacturer that integrates recycled steel into its production line. Instead of simply ignoring the recycled content, the “Allocation at the Point of Substitution” model recognizes that this recycled steel can replace virgin steel in other production processes. In practice, the environmental savings from displacing a raw material are credited back to the process. It’s like giving your recycled steel a “bonus” by offsetting part of the environmental burden. This approach aligns with the circular economy by acknowledging that recycled inputs offer tangible benefits when they substitute for more resource-intensive alternatives.

4. Substitution, Consequential, Long-Term
Lastly, consider a scenario where a major consumer goods company shifts to using recycled plastics. This decision not only affects the immediate production process but also sets off a chain reaction: reducing reliance on virgin plastics, stimulating market adjustments, and encouraging more sustainable practices industry-wide. The “Substitution, Consequential, Long-Term” model captures these ripple effects. By treating by-products as negative flows—essentially credits that offset burdens—it accounts for both the direct benefits and the long-term, dynamic shifts in the market. This approach is particularly useful when assessing policies or innovations that drive transformational change over time.

Each of Ecoinvent’s four system models offers a unique lens for evaluating the environmental impacts of products—empowering you with flexibility based on your study’s goals. Whether it’s pinpointing the core emissions of a process, aligning with industry regulations, unlocking the value of recycled resources, or forecasting market trends for long-term benefits, you can choose the approach that best fits your project requirements. This tailored strategy equips you with transparent, decision-friendly sustainability insights.