Direct CO₂ Emissions at Point of Generation (kg/MWh)
Energy Source
CO₂ Intensity (kg/MWh)
Coal
800-1,000
Natural Gas
400-500
Oil (Diesel)
700-900
Solar PV
0
Wind
0
Hydropower (Direct)
0
Nuclear
0
Lifecycle CO₂ Emissions (kg/MWh)
Energy Source
Lifecycle CO₂ Intensity (kg/MWh)
Coal
820-1,050
Natural Gas
450-600
Solar PV
20-50
Onshore Wind
10-20
Offshore Wind
15-30
Hydropower
50-200 (higher in tropics)
Nuclear
10-15
Biomass
100-250 (variable)
Key Lifecycle Emission Drivers for Low-Carbon Technologies
Solar PV: Polysilicon production, panel manufacturing, transport, and concrete foundations dominate emissions. Lifespan ~20-30 years; recycling limited by cost.
Wind: Steel, rare earth metals, concrete bases, and maintenance (gearbox/blade replacement) are primary sources.
Nuclear: Uranium mining/enrichment, plant construction materials, and long build times contribute most lifecycle emissions.
Hydropower: Methane emissions from tropical reservoirs can rival fossil fuels.
Biomass: Land use change, transport, and combustion emissions vary widely; can approach coal emissions.
Methane and Non-CO₂ Greenhouse Gas Impacts
Source
Impact
Notes
Natural Gas Fugitive Emissions
High
3-4% leakage negates climate benefit over coal; CH₄ ~85x CO₂ warming over 20 years
Oil Field Flaring
Moderate
Direct CO₂ and black carbon emissions, especially in Nigeria, Russia, Venezuela
Biomass
Variable
Combustion, transport, and regrowth lag cause significant emissions
Carbon Accounting and Policy Implications
Net-zero targets must include full lifecycle emissions, not just operational CO₂.
Carbon pricing should cover upstream and embodied emissions for accurate cost reflection.
Policies favoring technologies based solely on point-source emissions risk perverse incentives and higher real-world emissions.
Lifecycle emissions highlight the importance of supply chain transparency and sustainable material sourcing.
Data sources: NREL LCA Harmonization (2024-2025), IEA Global Energy Review 2025, IPCC AR6, Ember Global Electricity Review 2025, World Nuclear Association, peer-reviewed literature[9][10][11][12][13].
Downstream: Recycling not always practiced; panels last 20-30 years.
Wind:
Upstream: Steel, rare earths, concrete.
Ongoing: Gearbox/blade replacement.
Land use: Transmission adds indirect emissions if sited remotely.
Nuclear:
Upstream: Uranium mining/enrichment, concrete/steel for construction.
Long build times increase embedded emissions.
Once operational, among the lowest lifecycle emissions.
Hydropower:
Methane from tropical reservoirs can be substantial due to rotting biomass.
Biomass:
Land use, transport, and regrowth lag can make emissions comparable to coal.
Methane, Flaring, and Non-CO₂ GHGs
Natural gas:
Methane leakage (“fugitive emissions”) during extraction/transport can offset gas’s CO₂ advantage over coal.
Methane is 84-87x more potent than CO₂ over 20 years. Leakage rates above 3-4% can erase climate benefits.
Oil extraction:
Associated gas flaring adds CO₂ and black carbon.
Biomass:
Emissions from combustion, transport, and land-use change; regrowth takes years, not immediate.
Systemic vs. Symbolic Decarbonization
Lifecycle emissions show that “zero emissions” claims for renewables/nuclear only hold at the point of generation. True decarbonization requires accounting for all upstream and downstream impacts.
Front-loaded emissions: Building solar, wind, and batteries creates a short-term emissions spike before long-term savings are realized.
“Symbolic decarbonization”: Policies that ignore lifecycle GHGs risk shifting emissions upstream (e.g., rare earth mining in China for Western renewables).