Life Cycle Assessments of Energy Technologies
NREL is a leader in the field of life cycle assessment (LCA) of energy technologies, both renewable and conventional. Life cycle assessment is a standardized technique that tracks all material, energy, and pollutant flows of a system—from raw material extraction, manufacturing, transport, and construction to operation and end-of-life disposal. Life cycle assessment can help determine environmental burdens from "cradle to grave" and facilitate comparisons of energy technologies.
Life cycle assessments provide a well-established and comprehensive framework to compare renewable energy technologies with fossil-based and nuclear energy technologies.
Life cycle assessment methodologies have been evolving for a few decades and are now supported by international initiatives (UNEP and SETAC, 2010) and governed by standards (Cowie et al., 2006; ISO, 2006). A 4-part approach to LCA is widely accepted today:
- Stating the purpose of the study and appropriately identifying the boundaries of the study (Goal and Scope Definition)
- Quantifying the energy use and raw material inputs and environmental releases associated with each stage of the life cycle (Life Cycle Inventory)
- Interpreting the results of the inventory to assess the impacts on human health and the environment (Life Cycle Impact Assessment)
- Evaluating opportunities to reduce energy, material inputs, or environmental impacts along the life cycle (Improvement Analysis, or Interpretation)
The Electricity Generating LCA Framework shows the generalized life cycle stages for an energy technology.
Most of the hundreds of life cycle assessments published on electricity generation technologies over the last 30 years only assemble life cycle inventories, quantifying the emissions to the environment or the use of resources rather than reporting effects on environmental quality. In addition, the majority of the available literature on energy technologies is based on attributional LCAs. See IPCC Special Report on Renewable Energy Sources and Climate Change Mitigation: Renewable Energy in the Context of Sustainable Development for more information.
Life cycle greenhouse gas (GHG) emissions from renewable electricity generation technologies are generally less than from those from fossil fuel-based technologies. Comparisons also show that the proportion of GHG emissions from each life cycle stage differs by technology:
- For fossil-fueled technologies, fuel combustion during operation of the facility emits the vast majority of GHGs.
- For nuclear and renewable energy technologies, the majority of GHG emissions are upstream of operation.
- Most emissions for biopower are generated during feedstock production, where agricultural practices play an important role.
- For nuclear power, fuel processing stages are most important, and a significant share of GHG emissions is associated with construction and decommissioning.
- For other renewable technologies (solar, wind, hydropower, ocean and geothermal), most life cycle GHG emissions stem from component manufacturing and, to a lesser extent, facility construction.
Comparison of published results for each specific electricity generation technology is challenging, due to variation of methods and assumptions. Building on experience with performing energy system life cycle assessments, NREL has developed and applied an approach for reducing the uncertainty around estimates for environmental impacts of renewable and conventional electricity generation technologies through its LCA Harmonization Project. These "harmonized" results are intended to support decision making in the policy and research communities.
- Hsu, DD; Inman, D; Heath, GA; Wolfrum, EJ; Mann, MK; Aden, A. 2010. Life Cycle Environmental Impacts of Selected US Ethanol Production and Use Pathways in 2022. Environmental Science & Technology. 44 (13):5289-5297
- Whitaker M, Heath GA. 2009. Life-Cycle Assessment of the Use of Jatropha Biodiesel in Indian Locomotives (Revised). NREL/SR-6A2-44428.
- Burkhardt JJ; Heath GA; Turchi CS. 2011. Life Cycle Assessment of a Parabolic Trough Concentrating Solar Power Plant and the Impacts of Key Design Alternatives. Environmental Science & Technology. 45 (6), pp 2457–2464.
- "Life Cycle Assessment of Biomass Cofiring in a Coal-Fired Power Plant," Clean Products and Processes, by Pamela Spath and Margaret Mann.
- "Life Cycle Assessment of a Natural Gas Combined Cycle Power Generation System," by Pamela Spath and Margaret Mann.
For more information on life cycle assessment across energy technologies, see the IPCC Special Report on Renewable Energy Sources and Climate Change Mitigation: Renewable Energy in the Context of Sustainable Development publication.
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