Life Cycle Assessment (LCA) is an approach that is evaluated to obtain possible environmental impacts of a product throughout the products’ life cycle by gathering inputs and outputs of the production system.
Life Cycle Assessment Framework
ISO 14040 Standards demonstrate four phases of a Life Cycle Assessment Study. Figure 1 shows the Life Cycle Assessment Framework that is evaluated with the combination of Goal And Scope Definition, Life Cycle Inventory Analysis, Life Cycle Impact Assessment and Interpretation of Results. Arrows represent that all those four phases are related to each other.
Goal And Scope Definition
In goal and scope definition phase; aim and coverage of the study are defined. This section also includes functional unit and system boundary definitions(Jolliet et al., 2016).
Functional unit is an important component in a Life Cycle Assessment study which is a quantitive definition of the products’ function. After the functional unit of the system is defined; all inputs, outputs and environmental impacts are represented per functional unit. Thus comparison of the impact potentials can be done efficiently and developments for the system can be recommended by arranging inputs.
System boundary of the study is defined in goal and scope definition phase. In this step; it is indicated what is included and what is excluded in the study. LCA can be conducted with four approaches. In a cradle-to-grave approach, Life Cycle Assessment Study starts from the resource extraction and ends with the use phase or waste management. In cradle-to-gate approach, it starts with the resource extraction and ends with the part of the production step. If gate-to-gate approach is accepted, LCA is conducted between production steps(gates) or a specific process of the production throughout the life cycle. Gate-to-grave approach covers the activity after production which is transportation, use and waste management.
Life Cycle Inventory Analysis
In Life Cycle Inventory Analysis phase; inventory data which include all inputs and outputs of the system according to the accepted Life Cycle Assessment Approach are defined. All the data that are collected from the facility and also obtained during on-site observations are represented per functional unit. An inventory analysis includes all energy and water inputs, material flow, etc. Outputs cover solid wastes, wastewater, by-products and emissions to the atmosphere.
Life Cycle Impact Assessment
The data that is collected in the Life Cycle Inventory Analysis phase is used in the Life Cycle Impact Assessment(LCIA) step in order to calculate environmental impacts with the chosen Life Cycle Impact Assessment Method.
There are several Life Cycle Impact Assessment methods such as CML, IMPACT 2002+, TRACI, ReCiPe, USEtox, IPCC 2001, etc.
Many impact categories can be calculated in a Life Cycle Assessment study such as; Global Warming Potential (GWP), Photochemical Ozone Creation Potential(POCP), Ozone Layer Depletion (ODP), Acidification Potential (AP), Eutrophication Potential (EP), Human Toxicity Potential (HTP), Abiotic Depletion Potential (ADP), Freshwater Aquatic Ecotoxicity Potential (FAETP), Marine Aquatic Ecotoxicity Potential (MAETP), etc.
Figure 2 demonstrates the classification and characterization steps of a Life Cycle Assessment study. In classification step; inventory data are categorized according to environmental impact potential categories. In characterization step; emissions that cause environmental impacts are multiplied with the characterization factor.
Interpretation of the results phase is the last step of a Life Cycle Assessment Study. In this section, results that are calculated in the Life Cycle Impact Assessment step are interpreted.
Interpretations need to respond to the goal and scope of the study and respect the system boundary that is defined in the goal and scope definition phase.
Sensitivity analysis and uncertainty analysis take place in the interpretation section. Those analyses give an opportunity to provide reliable conclusions and recommendations to develop the process.