Life Cycle Assessment (LCA) in Environmental Engineering: ISO 14040 Metrics, Eco-Indicators, and Circular Systems
Life Cycle Assessment (LCA) is a standardized, cradle-to-grave analytical methodology used to evaluate the environmental impacts associated with a product, process, or civil infrastructure system throughout its lifecycle. Governed by ISO 14040 and ISO 14044 standards, LCA quantifies resource consumption, energy usage, and environmental emissions across four phases: Goal and Scope Definition, Life Cycle Inventory (LCI), Life Cycle Impact Assessment (LCIA), and Interpretation. In the Life Cycle Inventory phase, material and energy balance equations are formulated relative to a defined Functional Unit (FU) . The cumulative energy demand ($CED$) across $n$ life stages is calculated as: $$CED = \sum_{i=1}^{n} \left( E_{\text{direct}, i} + E_{\text{embodied}, i} \right) = \sum_{i=1}^{n} \left( m_i \cdot e_i + V_i \cdot \varepsilon_i \right)$$ Where $m_i$ is material mass, $e_i$ is specific embodied energy ($\text{MJ/kg}$), $V_i$ is energy volume/fuel consumed, and $\varepsilon_i$ is f...