Every Life Cycle Assessment starts with a fundamental choice: Are you building a model that describes where you've been, or one that explores where you could go? This isn't just about methodology; it's about purpose. Do you need numbers for documentation, reporting, and compliance? Or do you need a tool to investigate your improvement opportunities and understand the real-world consequences of your decisions?
Life Cycle Assessment (LCA) has become the gold standard for quantifying sustainability impacts. By incorporating a life cycle perspective and adopting holistic thinking, it allows us to see beyond isolated stages product life cycle. Its focus on relating impacts to the actual functions of products and services enables meaningful, system-level comparisons of different options, which helps us determine the most sustainable means to achieve desired outcomes.
It is therefore of course tacitly implied that the value of LCA as a method is to inform us of the best path forward and to provide optimal decision support. Consequently, it is paramount that our LCAs are conducted with this goal of reducing future environmental impacts in mind.
To serve this purpose, our models must emphasize causality and understanding the links between choices and effects. Since we are ultimately interested in understanding the consequences of change, and since those causal relationships are often complex and unintuitive, we need comprehensive methods that can represent such complexity. Only then can we develop a full picture before making decisions that shape the future of our planet.
Sadly, this lens is too often not applied in current LCAs, where often the focus is on mapping past emissions while normative methodological choices are made to isolate product systems from the context that they inhabit. While such retrospective studies can be informative, they may fail to provide decision-makers with the insight needed to anticipate the consequences of potential changes. When used as guidance, these backward-looking models risk answering the wrong questions, namely those describing the past rather than guiding the future.
An LCA is only as good as the question it answers. Be explicit: are you comparing alternatives, finding hotspots, or assessing the consequences of a decision? Without a clear goal, you may end up with a study that reports history instead of guiding action.
A key choice is between two approaches:
Understanding the difference helps you pick the right tool so your study answers the question that actually matters for your purpose.
CLCA, aims to model the environmental consequences of a decision or a change in the market. It focuses on how market demands and production systems would adjust if a product system were introduced or changed. CLCA answers questions like "What are the environmental implications of increasing the production of this product, or introducing a new alternative?" In other words, Consequential LCA answers how the environmental footprint of a product will be in the future based on factors like how the market changes.
Pros
Cons
ALCA aims to describe the environmental impacts “attributed” to a product or service within a specific supply chain. It typically models the physical flows to and from a product system, representing average or typical production processes. ALCA answers questions like "What is the environmental footprint of this product as it currently exists?" In other words, Attributional LCA answers how the environmental footprint of this product was in the past or how it currently exists.
Pros
Cons
While both methods have their place, CLCA is often more powerful for decision-making aimed at future impact reduction. It helps identify truly impactful interventions by focusing on market responses. ALCAs are often used for used for annual accounting and reporting, but there is a risk that the results by mistake are also used decision-making where two or more product systems are compared, even if it is clearly stated that the attributional LCA is not suitable for that purpose.
When to use CLCA:
When to use ALCA:
It is important to know that it is also possible to conduct a CLCA alongside the ALCA, so that the differences are clearly visible and explainable to the user, and so that the package can be used for both decision-making and reporting without risks of greenwashing challenges.
All LCAs start with a Goal and scope definition: Clearly define the purpose of the study, the product system to be assessed, the functional unit (the reference unit for comparison), system boundaries, and the environmental impacts to be evaluated. Each of these choices should be made to fit the specific question you need to answer.
Whether you are exploring LCA for the first time or looking to deepen your existing practices, We guide you through every step and ensure that your LCA follows the standards and methods most appropriate for your needs, so you end up with the right data to make the most effective decisions.
