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Life Cycle Assessment Harmonization

In this project, NREL reviewed and harmonized life cycle assessments (LCAs) of electricity generation technologies to reduce uncertainty around estimates for environmental impacts and increase the value of these assessments to the policymaking and research communities.

Hundreds of life cycle assessments have been published, with considerable variability in results. These variations in approach hampered comparison across studies and the pooling of published results. NREL harmonized these data to:

  • Understand the range of published results of LCAs of electricity generation technologies
  • Reduce the variability in published results
  • Clarify the central tendency of published estimates.

Chart that shows Electricity Generation Technologies Powered by Renewable Resources. For help reading this chart, please contact the webmaster.

Comparison of as-published life cycle GHG emission estimates for electricity generation technologies. The impacts of the land use change are excluded from this analysis.

The data showed that life cycle greenhouse gas (GHG) emissions from technologies powered by renewable resources are generally less than from those powered by fossil fuel-based resources. The central tendencies of all renewable technologies are between 400 and 1,000 g CO2eq/kWh lower than their fossil-fueled counterparts without carbon capture and sequestration (CCS).

Published Results

In the first phase of this project, NREL analyzed published life cycle GHG estimates for hydropower, ocean, geothermal, biopower, solar, wind, nuclear, coal, and natural gas technologies.

See the results of the review and analysis of published LCA estimates for these technologies:

Chart that shows life cycle greenhouse gas emissions for biopower technologies. For help reading this chart, please contact the webmaster.

Life cycle GHG emissions for biopower technologies per unit of electricity generation, including supply chain emissions

For more information, see:

Chart that shows life cycle greenhouse gas emissions for geothermal technologies.  For help reading this chart, please contact the webmaster.

Estimates of life cycle GHG emissions from geothermal power generation

For more information, see:

Chart that shows life cycle greenhouse gas emissions for hydropower technologies. For help reading this chart, please contact the webmaster.

Life cycle GHG emissions of hydropower technologies

For more information, see the IPPC Special Report on Renewable Energy Sources and Climate Change Mitigation: Hydropower (2011).

Chart that shows life cycle greenhouse gas emissions for ocean power technologies.  For help reading this chart, please contact the webmaster.

Estimates of life cycle GHG emissions of wave and tidal range technologies

For more information, see the IPPC Special Report on Renewable Energy Sources and Climate Change Mitigation: Ocean Energy (2011).

Harmonized Results

Chart that compares published and harmonized life cycle greenhouse gas emissions. For help reading this chart, please contact the webmaster.

Comparison of as-published and harmonized life cycle greenhouse gas emission estimates for selected electricity generation technologies.

In subsequent project phases, NREL adjusted the estimates to a consistent set of methods and assumptions specific to each technology. Like the published data, the harmonized data showed that life cycle greenhouse gas emissions from solar, wind, and nuclear technologies are considerably lower and less variable than emissions from technologies powered by combustion-based natural gas and coal.

Harmonization did not significantly change the central tendency (as indicated by the median value) of any of the technologies evaluated. Harmonization did, however, reduce the variability of GHG emissions estimates.

See the results from NREL's review, analysis, and harmonization of published life cycle assessment estimates for these technologies:

Chart that shows a side-by-side comparison of onshore and offshore wind.  For help reading this chart, please contact the webmaster.

Side-by-side comparison of central tendency and spread of as-published GHG emission estimates for wind power systems

For more information, see:

Chart that shows a side-by-side comparison of light water reactors, boiling water reactors, and pressurized water reactors.  For help reading this chart, please contact the webmaster.

Published and harmonized life cycle GHG emission distribution plots (Whiskers represent minimums and maximums. Boxes represent 25th percentile, median estimate, and 75th percentile.)

For more information, see:

Chart that shows a side-by-side comparison of coal-powered technologies. For help reading this chart, please contact the webmaster.

As-published and technology-specific harmonized estimates of life cycle GHG emissions for coal-fired electricity generation considering all four evaluated technologies as a group and each evaluated technology independently

For more information, see:

Chart that shows a side-by-side comparison of natural gas-fired technologies. For help reading this chart, please contact the webmaster.

Comparison of published to harmonized life cycle GHG emission estimates for natural gas electricity generation technologies using conventionally and unconventionally produced natural gas

For more information, see:

Data and Tools

Download and visualize numerical results and bibliographies on the OpenEI LCA Harmonization application.

Publications

IPCC Special Report on Renewable Energy Sources and Climate Change Mitigation (2011)

Meta-Analysis of Life Cycle Assessments, Journal of Industrial Ecology (2012)

Harmonization of Initial Estimates of Shale Gas Life Cycle Greenhouse Gas Emissions for Electric Power Generation, Proceedings of the National Academy of Sciences of the United States of America (2014)

Life Cycle Greenhouse Gas Emissions from Electricity Generation, NREL Fact Sheet (2013)

Contact

Garvin Heath

Garvin.Heath@nrel.gov | 303-384-7460