Life-cycle greenhouse-gas emissions of energy sources

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Comparisons of life-cycle greenhouse gas emissions attempt to calculate the emissions of greenhouse gases or solely carbon dioxide over the full life of a power source, from groundbreaking to fuel sources to waste management back to greenfield status. The IPCC in 2011 aggregated and harmonized the CO2 emission findings of hundreds of papers, which were published between 1980 and 2010.[1]

It is important to note that for all technologies, advances in efficiency and therefore reductions in CO2 emissions since the time of publication have not been included. For example, the total life cycle emissions from wind power may have reduced since publication, similarly, due to the timescales over which the studies were conducted, Nuclear power Generation II reactor CO2 emissions are stated, and not the emissions of Generation III reactors, which are presently under construction in the United States and China.

2011 IPCC aggregated results of the available literature[edit]

A literature review conducted by the Intergovernmental Panel on Climate Change in 2011, of numerous energy sources CO2 emissions per unit of electricity generated, found that the CO2 emission value, that fell within the 50th percentile of all total life cycle emissions studies were as follows.[2]

Lifecycle greenhouse gas emissions by electricity source.[2]
Technology Description 50th percentile
(g CO2/kWhe)
Hydroelectric reservoir 4
Wind onshore 12
Nuclear various generation II reactor types 16
Biomass various 18
Solar thermal parabolic trough 22
Geothermal hot dry rock 45
Solar PV Polycrystaline silicon 46
Natural gas various combined cycle turbines without scrubbing 469
Coal various generator types without scrubbing 1001
Estimated Lifecycle greenhouse gas emissions of carbonaceous fuels when coupled with carbon capture and storage.[2]
Technology Description Minimum estimate
(g CO2/kWhe
Maximum estimate
(g CO2/kWhe
Natural gas with CCS 65 245
Coal with CCS 98 396

2012 Yale University systematic review and harmonization of nuclear power data[edit]

A Yale University review published in the Journal of Industrial Ecology analyzing CO2 life cycle assessment emissions from nuclear power determined that:[3]

"The collective LCA literature indicates that life cycle GHG emissions from nuclear power are only a fraction of traditional fossil sources and comparable to renewable technologies."

It went on to note that for the most common category of reactors, the Light water reactor:

"Harmonization decreased the median estimate for all LWR technology categories so that the medians of BWRs, PWRs, and all LWRs are similar, at approximately 12 g CO2-eq/kWh"

The study noted that:

"the difference between nuclear power life cycle GHG emissions constructed in an electric system dominated by nuclear (or renewables) and a system dominated by coal can be fairly large (in the range of 4 to 22 g CO2-eq/kWh compared to 30 to 110 g CO2-eq/kWh, respectively)"

Although the paper primarily dealt with data from Generation II reactors, and did not analyze the CO2 emissions by 2050 of the presently under construction Generation III reactors, it did summarize the Life Cycle Assessment findings of in development reactor technology's.

Theoretical FBRs [ Fast Breeder Reactors ] have been evaluated in the LCA literature. The limited literature that evaluates this potential future technology reports median life cycle GHG emissions ... similar to or lower than LWRs and purports to consume little or no uranium ore.

2008 Benjamin K. Sovacool survey of nuclear power.[edit]

According to Benjamin K. Sovacool, nuclear power plants produce electricity with about 66 g equivalent lifecycle carbon dioxide emissions per kWh, while renewable power generators produce electricity with 9.5-38 g carbon dioxide per kWh.[4]

A meta analysis of 103 nuclear power life-cycle studies by Benjamin K. Sovacool found that nuclear power plants produce electricity with a mean of 66 g equivalent life-cycle carbon dioxide emissions per kWh, compared to renewable power generators, which produce electricity with 9.5 to 38 g carbon dioxide per kWh and fossil-fuel power stations, which produce electricity with about 443 to 1,050 g equivalent lifecycle carbon dioxide emissions per kWh.[5][6][7]

Sovacool thus concludes that nuclear energy technologies are 7 to 16 times more effective than fossil fuel power plants on a per-kWh basis at fighting climate change, and renewable electricity technologies are "two to seven times more effective than nuclear power plants on a per kWh basis at fighting climate change." Sovacool has said that his estimates already include all conceivable emissions associated with the manufacturing, construction, installation and decommissioning of renewable power plants.[4]

On his nuclear power paper, Benjamin K. Sovacool has been criticized by his peers, as it was noted that his paper was overly based on data from Jan Willem Storm van Leeuwen.[8] Beerten et al. state:

"Most recently, Sovacool(2008) calculated a mean value for the overall emissions by averaging the global results of 19 LCA [Life-Cycle Analysis] studies forming a subset of, as stated by the author, 'the most current, original and transparent studies' out of 103 studies. However, a critical assessment reveals that a majority of the studies representing the upper part of the spectrum are studies that can be traced back to the same input data and performed by the same author, namely Storm van Leeuwen. After careful analysis, it must be concluded that the mix of selected LCAs results in a skewed and distorted collection of different results available in the literature. Furthermore, since many studies use different energy mixes and other assumptions, averaging GHG emissions of those studies is no sound method to calculate an overall emission coefficient, as it gives no site specific information needed for policy makers to base their decisions."[8]

Lifecycle greenhouse gas emission estimates for electricity generators, according to Benjamin K. Sovacool's comparison.[5]
Technology Description Estimate
(g CO2/kWhe)
Wind 2.5 MW offshore 9
Hydroelectric 3.1 MW reservoir 10
Wind 1.5 MW onshore 10
Biogas Anaerobic digestion 11
Hydroelectric 300 kW run-of-river 13
Solar thermal 80 MW parabolic trough 13
Biomass various 14-35
Solar PV Polycrystaline silicon 32
Geothermal 80 MW hot dry rock 38
Nuclear various reactor types 66
Natural gas various combined cycle turbines 443
Fuel Cell hydrogen from gas reforming 664
Diesel various generator and turbine types 778
Heavy oil various generator and turbine types 778
Coal various generator types with scrubbing 960
Coal various generator types without scrubbing 1050

Beerten et al. proceed to discuss reasons why LCA analysis for nuclear power plants can give such widely varying estimates. For example, life-cycle greenhouse-gas emissions of nuclear power depend on the used enrichment method, the carbon intensity of the electricity used for enrichment, the efficiency of the plant, as well as on chosen mining technologies.

However, Beerten et al. failed to mention that the Sovacool survey used multiple papers from e.g. Dones et al. which are at the very low end of estimates. However as discussed by Beerten et al. in their criticism of Sovacool's survey, by its very nature, the taking of an average/mean value from multiple sources which are generally in agreement and adding it to a single high value, will skew the result in that single outliers direction. This is why reporting values as percentile figures is preferred by the Intergovernmental Panel on Climate Change, to prevent conclusions from single outlier studies, which are prevalent not only when examining nuclear power, but in the literature of all energy sources,[9] skewing the greenhouse gas LCA values of energy sources upwards. An upwards skewing issue that would naturally likewise result if one took the mean value from the LCA results of every other energy source. Moreover the differences in methodology would not have been a large issue if Sovacool had stuck to consistently applying his averaging methodology to every other energy source before he concluded: Renewable electricity technologies are "two to seven times more effective than nuclear power plants on a per kWh basis at fighting climate change."

Had he likewise assessed renewable technologies by the same averaging/mean criteria that he lay down in his nuclear power paper, he would not have concluded this. Instead, Sovacool applied his particular methodology to nuclear power only and then simply compared his averaging result, from nuclear power, with the renewable values found by other researchers following entirely different methodologies.

2007 non-peer reviewed Oxford Research Group survey[edit]

A 2007 report published by the Oxford Research Group listed the following results, after Leeuwen and Smith: coal = 755 g/kWh; natural gas = 385 g/kWh; biomass = 29 - 62 g/kWh; wind = 11 - 37 g/kWh; nuclear = 11 - 130 g/kWh (using the minimum and maximum results amongst 3 studies). The report concluded that "Emissions from nuclear power lie somewhere between biomass and natural gas ... Furthermore, as the available average ore grade declines CO2 (and other Greenhouse Gases) emissions from nuclear power will increase." [7]

Other studies[edit]

"Hydropower-Internalised Costs and Externalised Benefits"; Frans H. Koch; International Energy Agency (IEA)-Implementing Agreement for Hydropower Technologies and Programmes; 2000.

In terms of individual studies, a wide range of estimates are made for many fuel sources which arise from the different methodologies used. Those on the low end tend to leave parts of the life cycle out of their analyses, while those on the high end often make unrealistic assumptions about the amount of energy used in some parts of the life cycle.[10]

The Intergovernmental Panel on Climate Change states that total life-cycle GHG emissions per unit of electricity produced from nuclear power are below 40 g CO2-eq/kWh (10 g C-eq/kWh), similar to those for renewable energy sources.[11]

Another report, Life-Cycle Energy Balance and Greenhouse Gas Emissions of Nuclear Energy in Australia, conducted by the University of Sydney in 2008 produced the following results: nuclear = 60-65 g CO2/kWh; wind power = 20 g/kWh; solar PV = 106 g/kWh. The likely range of values from this study produced the following results: nuclear = 10-130 g CO2/kWh; wind power = 13-40 g CO2/kWh; solar PV = 53-217 g CO2/kWh. Furthermore, the study criticised the Vattenfall report : "it omits the energy and greenhouse gas impacts of many upstream contributions".[12]

In a study conducted in 2006 by the UK's Parliamentary Office of Science and Technology (POST), which used figures from the Torness study,[13] nuclear power's life cycle was evaluated to emit the least amount of carbon dioxide (very close to wind power's life cycle emissions) when compared to the other alternatives (fossil fuel, coal, and some renewable energy including biomass and PV solar panels). [14]

A 2005 study,[15] issued by Jan Willem Storm van Leeuwen, reported that carbon dioxide emissions from nuclear power plants per kilowatt hour could range from 20% to 120% of those for natural gas-fired power stations depending on the availability of high grade ores.[15]

See also[edit]

References[edit]

  1. ^ Nuclear Power Results – Life Cycle Assessment Harmonization, NREL Laboratory, Alliance For Sustainable Energy LLC website, U.S. Department Of Energy, last updated: January 24, 2013.
  2. ^ a b c Moomaw, W., P. Burgherr, G. Heath, M. Lenzen, J. Nyboer, A. Verbruggen, 2011: Annex II: Methodology. In IPCC: Special Report on Renewable Energy Sources and Climate Change Mitigation (ref. page 10)
  3. ^ Warner, Ethan S.; Heath, Garvin A. Life Cycle Greenhouse Gas Emissions of Nuclear Electricity Generation: Systematic Review and Harmonization, Journal of Industrial Ecology, Yale University, published online April 17, 2012, doi: 10.1111/j.1530-9290.2012.00472.x.
  4. ^ a b Benjamin K. Sovacool. A Critical Evaluation of Nuclear Power and Renewable Electricity in Asia, Journal of Contemporary Asia, Vol. 40, No. 3, August 2010, p. 386.
  5. ^ a b Benjamin K. Sovacool. Valuing the greenhouse gas emissions from nuclear power: A critical survey. Energy Policy, Vol. 36, 2008, p. 2950.
  6. ^ "Valuing the Greenhouse Gas Emissions from Nuclear Power".  JournalistsResource.org, retrieved 22 March 2012
  7. ^ a b Edited by Frank Barnaby, James Kemp (2006). "Secure Energy? Civil Nuclear Power, Security and Global Warming". Oxford Research Group. Retrieved 2007-07-13. 
  8. ^ a b Beerten, Jef; Laes, Erik; D’haeseleer, William (December 2009). "Greenhouse gas emissions in the nuclear life cycle: A balanced appraisal". Energy Policy 37 (12): 5056–5068. doi:10.1016/j.enpol.2009.06.073. Retrieved 2 Mar 2012. 
  9. ^ http://onlinelibrary.wiley.com/doi/10.1111/j.1530-9290.2012.00464.x/full Life Cycle Greenhouse Gas Emissions of Utility-Scale Wind Power. Published estimates for wind power range from 1.7 to 81 grams CO2-equivalent per kilowatt-hour (g CO2-eq/kWh)
  10. ^ "Nuclear energy: assessing the emissions". Nature. September 2008. Retrieved 18 May 2010. 
  11. ^ IPCC (2007). "Climate Change 2007: Working Group III: Mitigation of Climate Change". 
  12. ^ Lenzen, M.; Frank Barnaby, James Kemp and others (2008). "Life cycle energy and greenhouse gas emissions of nuclear energy: A review. Energy Conversion and Management 49, 2178-2199". University of Sydney. Retrieved 2007-07-13. 
  13. ^ AEA Technology environment (May 2005). "Environmental Product Declaration of Electricity from Torness Nuclear Power Station". Retrieved 31 January 2010. 
  14. ^ Parliamentary Office of Science and Technology (2006). "Carbon Footprint of Electricity Generation". Retrieved 2007-07-13. 
  15. ^ a b Storm van Leeuwen and Philip Smith (2003). "Nuclear Power — The Energy Balance". Retrieved 2006-11-10. 

External links[edit]