Life Cycle Assessment Notes

LCA Process

• Four main processes:

  • Scope and definition

  • Inventory analysis

  • Impact assessment

  • Interpretation of results

Goal Definition

• Define the objective of the study.

• Determine the starting and ending points of the process.

• Define the methods to be used.

• Identify parameters to be measured.

Scope Definition

• Define the boundaries of the study.

• Example: Carbon Nanotube (CNT) synthesis:

  • Base plastic material collection

  • Shredding

  • Pretreatment (may or may not be needed)

  • Chemical Vapor Deposition (CVD) synthesis

  • Post-treatment (chemical or heat)

Inventory Analysis

• LCA studies are data-driven.

• Data is required for each step of the process.

• Data sources:

  • Literature

  • Databases

  • Experimental work

  • Assumptions may be necessary

Data Collection

• Collect data relevant to the defined scope.

• Make necessary assumptions.

• Source data from:

  • Literature

  • Databases

  • Government research

  • International agencies (IEA, UN, etc.)

• Assess the authenticity and reliability of data.

Data Preference

• Primary data (collected directly from industries/factories) is more valuable and improves accuracy.

• Secondary data (from literature) is often used due to the difficulty of obtaining primary data.

• Experimental data is also used.

Data Compilation

• Split data based on the defined scope and steps.

• Collect inventory data from start to end.

• Identify data requirements for each step.

Impact Assessment

• Calculation based on inventory data.

• Can be done using software or manual calculations.

• Data needs to be in a standard, normalized unit.

• Climate Change Example:

  • Caused by gases like carbon dioxide, methane, nitrous oxide ($N_2O$), water vapor, and hydrofluorocarbons.

  • Quantified into a single unit for comparison.

• Impact Categories:

  • Global Warming Potential (GWP)

  • Acidification Potential

  • Ozone Depletion Potential

  • Human Toxicity

  • Eutrophication

  • Auto Oxidation Potential

  • Solid Waste

  • Ecotoxicity

• Data from inventory is converted using conversion and emission factors.

• Global Warming Potential (GWP) Example:

  • Represented as kilogram carbon dioxide equivalent ($kg CO_2$ equivalent).

  • Methane conversion factor: 21

  • Nitrous oxide conversion factor: 310-320

  • Calculations are compiled (e.g., in Excel).

Interpretation of Results

• Compare results with previous literature.

• Interpret whether results are favorable.

• Analyze why results are higher or lower than expected.

• Identify the safest or best pathway for material production.

• This stage defines the outcome and objective of the study.

Iterative Process

• Life Cycle Assessment is an iterative process.

• The arrows in the diagram are double-sided, indicating that the process can go back and forth between stages.

• Interpretation of results is connected to all three parameters (scope, inventory, impact assessment).

• Accuracy depends on the authenticity of data.

System Boundary

• Defines the scope: from start to end of the project.

• Cradle-to-gate approach: from raw material extraction to the factory gate.

• Factory gate: point before retailer, wholesaler, or final consumer.

• Example of CNTs: sourced from plastics (or biomass).

• Steps:

  • Plastic sourcing

  • Pre-treatment

  • CVD method (or pyrolysis/microwave)

  • Purified CNTs ($P r C N T$) - treating it with acid

Key Parameters within System Boundary

• Energy Input: required for each process step.

• Emission Output: released during each process step. *Energy Input:

  • Electricity powers processes, especially CVD.

  • Equipment has a power rating.

  • Indirect emissions result from electricity production methods.

  • Regional variations in emissions per kilowatt-hour.
    $1.1 kg CO_2$ per kilowatt hour in Uttarakhand (example).

• Regional disparities in energy inputs and emissions exist.

  • Only three things are really important for system boundary

    • Energy, Substance Route, Emissions

Functional Unit

• Reference material for comparison.

• Example: 1 gram of CNT.

• Used as a basis for comparing CNT synthesis impacts.

• Yield adjustments may be needed to ensure functional unit represents an approximate value.

  • Not a control variable kind of thing

  • Different methods of CNT synthesis will vary in yield

• Example:

  • 5 grams of PET + 5 grams of paracetamol → 1.2 grams of CNTs.

  • Adjust input parameters so that the functional unit is 1 gram.

• Functional unit: reference point for comparing environmental impact and energy production.

• Assumed in a particular study for LCA purposes.

• Ensures a level playing field when comparing different materials or processes.

• Allows for the comparison of materials with the same quantities.

Further Steps (To be Discussed Next Time)

• Calculations: require a dedicated session (30-40 minutes).

• Previous Process of Plastic: Determine the amount of energy required for production (e.g., 10 grams of plastic).

• Evaluate energy consumption (kilojoules, megajoules).

• Determine environmental impact (GWP, AP, etc.).

*For producing 10 grams of plastic:
*How much energy is required?
*What is the environmental impact?

Tentative Data

• Find existing literature on energy requirements and environmental impact for plastic production.

• Compare different plastics.
  LCA is always comparative early.

• Assume transportation distance to the facility (e.g., 15-20 kilometers).

• CVD emissions are mostly indirect (electricity consumption).

Research Task

• Determine the energy consumption and environmental impact for producing 10 grams of various plastics (polyethylene, polyester, mixed plastics).

• Focus on one country (U.S. or India).
  *First, India. If there are no results, consider the US.

• If the data is available from the US, take the electricity consumption and environmental impact of the USA and say it must be uniform somewhere.

Study Focus

*Find how much amount of energy is required to produce 10g of particular plastic
*What are the emissions?