LCA for Energy and Power Generation

Energy production is central to climate change and environmental sustainability. Life Cycle Assessment of electricity generation technologies reveals that impacts extend far beyond operational emissions—embodied carbon in infrastructure, fuel supply chains, and end-of-life considerations all matter significantly.

Why LCA for Energy?

Foundation of other LCAs: Electricity is an input to virtually every product and process. Energy LCA data forms the backbone of most LCI databases.

Technology comparison: Debates about nuclear vs. solar, wind vs. gas, and grid-scale storage require life cycle evidence.

Policy relevance: Energy policy decisions—subsidies, phase-outs, grid planning—benefit from comprehensive impact assessment.

Climate targets: Electricity decarbonization is essential for climate goals; LCA shows which pathways actually reduce emissions.

Emerging technologies: Hydrogen, carbon capture, and advanced renewables need life cycle evaluation before large-scale deployment.

Methodological Considerations

Functional Unit

Energy LCA typically uses:

Per unit of electricity: "1 kWh (or 1 MWh) of electricity delivered to the grid"

• Most common functional unit
• Doesn't account for dispatchability

Per unit of capacity: "1 MW of installed capacity over 25-year lifetime"

• Accounts for capacity factor differences
• Useful for infrastructure comparisons

System services: "1 MW of dispatchable capacity"

• Accounts for intermittency
• Requires storage/backup allocation

System Boundary Choices

Capacity Factor and Lifetime

Results are highly sensitive to utilization assumptions:

Technology Profiles

Fossil Fuels

Coal

• Dominant impacts: Combustion CO₂ (80-90% of GWP)
• Other concerns: Mining impacts, ash disposal, mercury emissions
• Typical GWP: 800-1,200 g CO₂e/kWh
• Key variables: Plant efficiency, coal type, transport distance

Natural Gas (CCGT)

• Dominant impacts: Combustion CO₂ (70-80%), methane leakage (10-20%)
• Other concerns: Fracking impacts (unconventional), infrastructure
• Typical GWP: 400-550 g CO₂e/kWh
• Key variables: Methane leakage rate, plant efficiency

Oil

• Limited role: Primarily backup/islands
• Typical GWP: 700-900 g CO₂e/kWh

Nuclear

Key characteristics:

• Very low operational emissions
• Significant construction and fuel cycle impacts
• Unique waste management requirements
• Long plant lifetimes

Impact distribution:

Typical GWP: 5-25 g CO₂e/kWh

Methodological issues:

• Long time horizons complicate assessment
• Waste storage for millennia—how to account?
• Accident risk—included in LCA or separate risk assessment?

Wind Power

Onshore wind

• Typical GWP: 7-15 g CO₂e/kWh
• Dominant impacts: Tower and foundation (steel, concrete)
• Key variables: Capacity factor, turbine size, lifetime

Offshore wind

• Typical GWP: 10-25 g CO₂e/kWh
• Additional impacts: Foundation type, installation vessels, cables
• Higher capacity factors partially offset additional infrastructure

Impact distribution (typical):

Solar Photovoltaics

Crystalline silicon (c-Si)

• Typical GWP: 20-50 g CO₂e/kWh
• Dominant impacts: Silicon purification, cell manufacturing
• Key variables: Manufacturing location (grid carbon), efficiency, lifetime

Thin-film (CdTe, CIGS)

• Typical GWP: 15-40 g CO₂e/kWh
• Lower energy manufacturing, but material concerns

Impact drivers:

Hydropower

Reservoir hydro

• Typical GWP: 4-30 g CO₂e/kWh (temperate)
• Tropical reservoirs: 100-2,000+ g CO₂e/kWh (methane from flooded biomass)
• Long lifetimes: 50-100+ years

Run-of-river

• Typical GWP: 2-10 g CO₂e/kWh
• Lower infrastructure impacts

Key issues:

• Tropical reservoir emissions (methane from decomposition)
• Ecosystem and land use impacts
• Social impacts (displacement)—not captured in standard LCA

Emerging Technologies

Hydrogen (for energy storage/transport)

• Green hydrogen (electrolysis + renewables): Low GWP but efficiency losses
• Grey hydrogen (SMR): High GWP (~10 kg CO₂/kg H₂)
• Blue hydrogen (SMR + CCS): Moderate GWP, depends on capture rate and methane leakage

Carbon Capture and Storage (CCS)

• Reduces plant emissions 85-95%
• Energy penalty increases upstream impacts
• Storage permanence assumptions matter

Geothermal

• Typical GWP: 15-55 g CO₂e/kWh
• Varies with reservoir type and emissions

Comparative Results

GWP Summary (g CO₂e/kWh)

Ranges reflect variation in technology, location, and methodology. Based on IPCC and peer-reviewed literature.

Beyond Climate Change

Grid-Level Analysis

Average vs. Marginal Emissions

Average grid emissions: Total emissions / total generation

• Used for attributional LCA
• Represents the grid as it currently exists

Marginal grid emissions: Emissions from the next kWh produced

• Used for consequential LCA
• Represents what happens when demand increases

Marginal emissions are often higher than average (gas peakers, coal plants operate at margins) but this varies by time, season, and grid.

Time-Dependent Impacts

Grid emissions vary significantly by:

• Time of day (solar peaks midday, wind varies)
• Season (heating/cooling loads)
• Year (grid evolves toward decarbonization)

For use-phase impacts (EVs, heat pumps), time-dependent assessment may be more appropriate than annual averages.

Data Sources

Key Databases and Resources

NREL LCA Harmonization Project

NREL conducted systematic harmonization of published LCAs for major technologies, providing consistent comparison by:

• Standardizing capacity factors, lifetimes, and boundaries
• Identifying sources of variation
• Providing harmonized ranges for policy use

Key Takeaways

1. Renewable and nuclear technologies have order-of-magnitude lower life cycle GWP than fossil fuels
2. Capacity factor and lifetime are critical—location-specific assessment is essential
3. Manufacturing location matters significantly for solar PV
4. Tropical hydropower can have high emissions from reservoir methane
5. Methane leakage assumptions are critical for natural gas assessment
6. Grid-level analysis requires distinguishing average from marginal impacts
7. Non-climate impacts (land, water, materials) vary differently than climate impacts

Resource List

Key Publications

• IPCC AR6 WG III, Chapter 6 (Energy Systems)
• NREL Life Cycle Assessment Harmonization Project
• UNECE Life Cycle Assessment of Electricity Generation Options

Data and Tools

• NREL LCA Commons
• ecoinvent
• Electricity Maps
• EPA eGRID

Organizations

• IEA
• IRENA

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Energy LCA is foundational to most other assessments. When using electricity in product LCAs, ensure the grid mix matches your manufacturing and use locations.