Dealing with Emergy Algebra in the Life Cycle Assessment Framework

Life Cycle Inventory (LCI) represents one of the four steps of the Life Cycle Assessment (LCA) methodology, which is a standardized procedure (ISO 14040:2006) to estimate the environmental impacts generated by the production, use and delivery of goods and services and final waste disposal. The calculation of emergy using LCI databases is acknowledged to be of great advantage to improve the accuracy and transparency of the emergy results and their reliability for a broader policy makers and stakeholders’ community. The compatibility with the emergy algebra rules is not straightforward for complex process-based LCI models, which (differently than the emergy rationale) keep a logic of conservation and allocate resources among co-products. This aspect has so far limited a consistent calculation of emergy in an LCA framework. The aim of this position paper is to describe the challenges to overcome in order to implement emergy accounting in LCA and specifically to outline possible research paths related to the implementation of the emergy algebra into LCIs. The Ecoinvent database is taken as a reference system, since it represents one of the most advanced LCI databases in terms of data quality and models, with around 4,200 LCI unit processes (i.e. energy generation, materials and agri-food production, infrastructure and transportation). It is structured in a large and complex matrix system with thousands of connections and loops between products and processes. We argue that the implementation of the emergy method and calculation within Ecoinvent and other LCI databases could follow two different paths: 1) rigorously following the database structure, i.e. the network of processes used for the emergy calculation and implicitly assuming that the relation between the processes and products are those existent in the database, or 2) not entirely following the emergy rules (with formal and comprehensive justification), i.e. considering the database network as different from the processes network in the real world and consequently only partially implementing the emergy algebra, following several simplifying hypotheses. The benefits and drawbacks of the two approaches are investigated toward a formal definition of a consistent approach.