Carbon Footprint and Life Cycle Assessment of Electric Vehicles

Relevant Greenhouse Gases in the Transportation Sector

• Distinction of Greenhouse Effects:

  • Natural Greenhouse Effect: The atmospheric warming caused by naturally occurring gases that allow solar radiation to reach the Earth but trap reflected heat.
  • Anthropogenic Greenhouse Effect: The additional warming caused by human activities (e.g., industrial processes, transportation, agriculture).

• Key Greenhouse Gases (GHG):

  • Water vapor ($H_2O$)
  • Carbon dioxide ($CO_2$)
  • Methane ($CH_4$)
  • Ozone ($O_3$)
  • Nitrous oxide ($N_2O$)

• Factors Influencing a Gas's Impact:

  • Radiation Properties: How effectively the gas absorbs and re-emits infrared radiation.
  • Dwell Time (Lifetime): The duration the gas stays in the atmosphere before being removed by natural processes.

• Global Warming Potential (GWP):

  • The UN Intergovernmental Panel on Climate Change (IPCC) publishes GWP values to standardize the impact of various gases relative to $CO_2$ over specific time horizons.

• Calculation of Climate Change Potential:
  • $\text{Climate Change Potential} = \sum_{i} GWP_i \times m_i$
  • Unit: $kg\,CO_{2eq.}$ ($CO_2$-equivalent).
  • Goal: To achieve comparability of diverse GHG emissions.

Emission Classification and Well-to-Wheel (WtW) Considerations

• System Boundaries for Emissions:

  • Tank-to-Wheel (TtW): Direct emissions, tailpipe emissions, or direct emissions during vehicle operation.
  • Well-to-Tank (WtT): Upstream emissions, indirect emissions, covering fuel/energy production and transport.
  • Well-to-Wheel (WtW): The total balance of TtW and WtT emissions. If available, charging efficiency ($\eta = 94\,\%$) is factored into WtT/WtW for electric vehicles.

• Perspective Shift: While manufacturer specifications and legal regulations typically refer to direct tailpipe emissions ($TtW$), a full system extension is necessary for Electric Vehicles (EVs) to include manufacturing and electricity generation balances ($WtW$).

Global and Sectoral CO2 Emission Trends

• Worldwide CO2 Emissions (1960–2024):

  • Emissions have grown from approximately $10,000\,million\,tons$ in 1960 to over $35,000\,million\,tons$ by 2020.
  • The 2024 estimate is approximately $37.4\,billion\,metric\,tons$.

• Breakdown by Sector (2022 Data):

  • Energy industry: $38.08\,\%$
  • Transportation: $20.68\,\%$
  • Industrial combustion: $16.97\,\%$
  • Buildings and facilities: $8.88\,\%$
  • Processing technology: $8.38\,\%$
  • Fuel utilization: $6.57\,\%$
  • Others: $0.44\,\%$

• Emissions in Germany:

  • Sector breakdown includes Energy Industry, Industry, Building, Transportation, Agriculture, and Waste Management.
  • The Climate Protection Act (CPA) goal for 2030 aims for significantly lower million tons of $CO_{2eq.}$ compared to 2010–2022 levels.

Electricity Mix and Environmental Impact

• GHG Emissions per kWh in the EU (2022):

  • Sweden: $7\,g\,CO_{2eq}/kWh$
  • France: $68\,g\,CO_{2eq}/kWh$
  • EU Average: $251\,g\,CO_{2eq}/kWh$
  • Germany: $366\,g\,CO_{2eq}/kWh$
  • Poland: $666\,g\,CO_{2eq}/kWh$

• Breakdown by Power Plant Type (Germany 2022):

  • Brown coal: $1233\,g\,CO_{2eq}/kWh$ ($988\,g$ is $CO_2$, the rest is other GHG).
  • Hard coal: $831\,g\,CO_{2eq}/kWh$
  • Natural gas: $491\,g\,CO_{2eq}/kWh$
  • Wind (onshore): $8\,g\,CO_{2eq}/kWh$
  • Solar/PV: $53\,g\,CO_{2eq}/kWh$
  • Nuclear: $12\,g\,CO_{2eq}/kWh$

• German Electricity Mix Composition (2025 Example):

  • Wind Onshore: $26.8\,\%$
  • Fossil Brown Coal/Lignite: $17.2\,\%$
  • Solar: $14.2\,\%$
  • Fossil Gas: $11.7\,\%$
  • Biomass: $8.9\,\%$
  • Wind Offshore: $6.2\,\%$
  • Fossil Hard Coal: $5.8\,\%$

• German Electricity Mix Trends:

  • 1990: $764\,g\,CO_{2eq}/kWh$
  • 2022: $434\,g\,CO_{2eq}/kWh$
  • Goal for 2050: Dominance of Wind ($51.8\,\%$) and Solar ($22.6\,\%$—forecast).

Comparative Analysis: Gasoline vs. Electric (WtW)

• Scenario 1: EU Electricity Mix

  • Golf 8 1.5 TSI (Gasoline): Consumption $5.1\,L/100\,km$. Total emissions: $165.3\,g\,CO_{2eq}/km$.
  • ID.3 Pro Performance (EV): Consumption $16.1\,kWh/100\,km$. EU Mix emissions ($295.8\,g\,CO_{2eq}/kWh$) with $\eta = 90\,\%$. Total: $52.9\,g\,CO_{2eq}/km$.

• Scenario 2: Brown Coal Generation

  • Generating electricity purely from brown coal ($1009\,g\,CO_{2eq}/kWh$) causes the ID.3 emissions to rise to $180.5\,g\,CO_{2eq}/km$, making it worse than the gasoline Golf.

Transportation of Natural Gases and Methane Slip

• Compressed Natural Gas (CNG): Transport distance significantly impacts the footprint due to methane leaks along pipelines.
  • Pipeline 1000km: $248\,g\,CO_{2eq}/kg$
  • Pipeline 7000km (Siberia): $1003.4\,g\,CO_{2eq}/kg$ ($663.0\,g\,CO_2$, $327.0\,g\,CH_4$, $13.4\,g\,N_2O$).
• Case Comparison (Diesel vs. CNG):
  • Golf 8 2.0 TDI (Diesel): $152.2\,g\,CO_{2eq}/km$
  • Seat Leon 1.5 TGI (CNG from Siberia): $155.1\,g\,CO_{2eq}/km$. The "Methane Slip" during engine operation contributes to this high value.

Analysis of Biofuels

• Biofuel GHG Balances (g CO2-eq/L):

  • Ethanol (Sugar Beets): Production emits $802\,g$, but receives a credit of $-1519\,g$. Net: $-717\,g$.
  • FAME (Sunflower Seeds): Net: $-1646\,g$.
  • Comparison (Gasoline vs. Ethanol): Total WtW for Ethanol is $86\,g\,CO_{2eq}/km$ vs. $165.3\,g\,CO_{2eq}/km$ for Gasoline.

• Limits of Biofuel Use:

  • Yield Estimation (Ethanol from grain): $1650\,L\,gasoline\,equivalent/ha$.
  • Total German agricultural land is $17\,million\,ha$. To replace all gasoline/diesel with biofuels would require approx. $41.4\,million\,ha$ (more than the total area of Germany - $35.7\,million\,ha$).
  • Food Competition: High biofuel demand competes with land needed for food and pet food.

Sustainability Methods for Electric Vehicles

• Methods for Composition of Charging Current:

  • Mix Method: Uses the average electricity mix of the grid.
  • Delta Method: Considers the additional power plants that must be brought online to meet the charging demand (often coal-heavy).
  • Parallel-Market Method: Based on specific green electricity contracts.

• Evaluation Findings:

  • Emissions: Generally lower for EVs in the EU, except in coal-heavy countries (DE, PL) when using the Delta method.
  • Efficiency: EVs have higher well-to-wheel efficiency in all EU countries across all methods.
  • Economic Outlook: From 2025 onwards, economic costs for $CO_2$ reduction using EVs are lower than for ICEVs due to rising certificate prices.

Life Cycle Assessment (LCA) Methodology

• Standardization: ISO 14040/14044.

• Four Phases of LCA:

  1. Objective and scope of investigation (Functional unit, e.g., mileage in km).
  2. Life cycle inventory (Material flows).
  3. Impact assessment.
  4. Evaluation.

• System Subdivisions:

  • Production (Extraction of raw materials + manufacturing).
  • Fuel supply (WtT).
  • Driving emissions (TtW).
  • Recycling (Negligible for ICEVs, higher for EVs due to batteries).

LCA Case Studies and Results

• VW Golf VI vs VII: GHG emissions reduced from $25.7\,tons$ to $22.2\,tons$ over the life cycle.

• VW Passat 1.4 TSI: Production emits approx. $7.4\,t\,CO_{2eq.}$ usage emits approx. $29\,t\,CO_{2eq.}$ over 10 years.

• VW up! vs e-up!:

  • Production: e-up! ($EV$) > up! ($ICEV$) due to battery manufacturing.
  • Usage: e-up! < up! (especially with green power).
  • Recycling: e-up! > up!.

• Global Context (Per Capita Emissions 2021):

  • Germany: $9.7\,t\,CO_{2eq.}/capita$
  • USA: $14.2\,t\,CO_{2eq.}/capita$
  • India: $1.9\,t\,CO_{2eq.}/capita$
  • World Target for $2^\circ C$: Higher reductions required across the board.

Environmental Impact Categories

LCAs analyze more than just global warming:

• GWP (Global Warming Potential): Measure of greenhouse effect.
• POCP (Photochemical Ozone Creation Potential): High-level pollution causing summer smog / ground-level ozone (Unit: $kg\,C_2H_{4eq}$).
• AP (Acidification Potential): "Acid rain" caused by emissions like $SO_2$ or $NO_x$ (Unit: $kg\,SO_{2eq}$).
• ODP (Ozone Depletion Potential): Destruction of the stratospheric ozone layer (Unit: $g\,R11_{eq}$).
• EP (Eutrophication Potential): Overfertilization of waters and soils with nutrients (Unit: $kg\,PO_{4eq}$).

Summary Key Questions

• Drive evaluated? By comparing the unit $CO_2$ equivalent and analyzing environmental damage throughout the full life cycle.
• Classification? Splitting into raw material extraction, production, WtW, and recycling.
• LCA results? Assessments provide damage analysis across various categories beyond just warming potential.
• Most eco-friendly drive? Depends on the definition of "eco-friendly" (e.g., carbon-focused vs. acid-focused vs. eutrophication-focused).