Producers' Comments

Nuclear and Hydroelectric power producers estimate lower emissions of CO2 than other analysts give. They have only limited explanations, which are given below.

NUCLEAR

The Swedish Nuclear power producer, Vattenfall, says they are bound by confidentiality agreements. They cite their full study at http://www.environdec.com/reg/021/dokument/EPDforsmark2007.pdf

An email on 23 April 2009 said:

• p. 10-11 will give you some more information on mines and the uranium amounts in the different processing steps. I can not give you any input numbers regarding our suppliers since we have promised not to do so.
• You can however find a lot of information on the homepages of the mining companies and in Australia they have a public national database with a lot of information and numbers http://www.npi.gove.au/
• Concrete production data have been taken from the Suisse ecoinvent database and include CO2 from calcining. I cannot give you data from this database since we have bought a license and signed a contract not to disseminate single datasets.
• We have used steel production data (excluding the end of life recycling credit) from IISI (International Iron and Steel Institute). These data you can get for free if you contact them and tell them how you will use their data.
• Main construction material in our largest reactor (BWR, light water) 1170 MW is (earthquake safe, Swedish conditions)
• Steel tot 29 ton/MW
• Concrete 369 ton/MW
• Copper   0,9 ton/MW
• Here you'll find the methodology used: http://www.environdec.com/pcr/pcr0708e.pdf
• Construction of transmission and distribution networks has been taken from the Suisse ecoinvent database www.ecoinvent.org

Vattenfall also told a conference they use other sources for impact of these materials:

• Primary copper: ICA (International Copper Association)
• Copper products: European Copper Institut (Deutsches K upferinstitut – Life Cycle Center)
• Electricity: ecoinvent Data combined with IEA (International Energy Agency) statistics on
• electricity generation mixes for nations, regions etc.
• Fuels: ecoinvent
• Aluminium: EAA (European Aluminium Association)
• Plastics: PE Plastics Europe (former APME Association of Plastics Manufacturers in Europe)
• Chemicals: PE Plastics Europe (former APME Association of Plastics Manufacturers in Europe), and ecoinvent
• Electronic components: EIME (Environmental Information and Management Explorer) EcoBilan
• Transports: NTM or regional alternatives1
• Waste management, other construction material: ecoinvent

The Swiss Nuclear power producer, NOK, provides the answers indented below. They did not provide data on their mines or amounts of material used in construction. They did say that they omit the CO2 from mining bentonite to protect waste permanently. Page numbers refer to the full Swiss study at http://www.environdec.com/reg/epd144e.pdf]

Generally, all emission factors for background processes (e.g. production of concrete, steel or chemicals) as well as emission factors for transport services were taken from the ecoinvent database (http://ecoinvent.org/). The database provides very detailed documentation for all modeled processes and also includes information on e.g. CO2 emissions from concrete production.

CO2List.org asked the following questions, and NOK gave the indented answers in an email on 4 May, 2009:

p.18 shows grams of greenhouse gases for 10 categories. Is there any more detail about how these 10 numbers were calculated? For example what were the fuel and production at the ISL mine or the other upstream processes? Or the concrete, steel or money used in construction, with factors for greenhouse gases? Does the concrete include just heat, or also the CO2 released from calcining CaCO3 => CaO + CO2 ?

• The CO2 released from calcining is included. Check ecoinvent documentation for details.
  

p.35 describes permanent waste storage in a mountain, and p.18 shows 0,51 g CO2e/kWh for "waste treatment." Does this number include the permanent storage? Excavating the caverns as well as mining and placing the bentonite? I assume it does not include any permanent office or guards to warn people away from the area.

• The number includes all aspects of the final repositories for all waste types. In addition to the excavation of the caverns and bentonite filling also the construction of storage casks as well as the construction and dismantling of an encapsulation facility is considered. The environmental impact of guards or a permanent office building is negligible compared to other activities and has therefore not taken into account.
  

p.9 gives the number of kilometers of transmission network for two voltages, and p.25 says grid infrastructure emits 0,151 g CO2e/kWh. Is the CO2/kilometer needed for construction the same for both voltages, or what are the factors for each voltage?

• Emission factors are not the same for the all voltages as different materials in different quantities are used. Emission factors for the construction of transmission networks were taken from the ecoinvent database.
  

HYDROELECTRICITY

The Swedish Hydroelectric producer, Vattenfall, uses data at odds with other researchers, to report low emissions, of 3.1 g CO2/kWh (0.007 pounds/kWh) from flooding the land. Their full study is at http://www.environdec.com/reg/088/dokument/08_waterEPD.pdf.

They give the explanation indented below. The explanation cites Adams of Oak Ridge National Lab for a figure of 10,000 tonnes of Carbon per square kilometer of Boreal soil (100 tonnes/hectare). Adams' data are at http://www.esd.ornl.gov/projects/qen/carbon12.html and actually show 129 tonnes of Carbon per hectare of Boreal soil, not 100. Later figures from Oak Ridge (Houghton & Hackler 2001) say 206 tonnes per hectare in Boreal soil. Vattenfall assumes only half of their low figure of 100 tonnes does decay.

Furthermore the Carbon in surface vegetation removed before inundation also needs to be counted, since it decays or burns (a small part would have been made into products which in turn are disposed of during  the 100 year time frame Vattenfall uses).

Vattenfall also says their reservoirs absorb CO2, through the action of algae, though a variety of researchers have measured gas exchanged at reservoir surfaces, and find CO2 being generated, not absorbed.

All these figures and sources are compared in the spreadsheet. Vattenfall's explanation follows, from an email on 15 April, 2009:

• The vegetation is removed before inundation, but there is still carbon in the ground itself and according to the ORNL database (Adams 1998), it amounts to 10 000 ton/km2 in boreal areas and 50% is assumed to degenerate during 100 years (which has been assumed to be the technical service life of the dams and water storages).
• Since the water flow becomes slower when building a dam there will also be an uptake of CO2 in growing biomass (algae etc) the amount depending also on latitude and in larger storages there will also be a renewed binding of carbon in the sediments after some time. "
• Adams, D. D. and Van Eck, G. T. M. (1988) Biogeochemical cycling of organic carbon in the sediments of the Grote Rug reservoir. - Archiv für Hydrobiologie, Supplement. 31:319-330.
• Adams, J. (1998) An inventory of data, for reconstructing 'natural steady state' carbon storage in terrestrial ecosystems. - ORNL, Tennessee, USA: INQUA Terrestrial Carbon Commission Resource.
• Axelsson, E. (1999) A life cycle assessment perspective on hydroelectric power, greenhouse gases and biodiversity. - Stockholm, Sweden: University of Stockholm; B.Sc.Thesis.
• Bergström, A.-K., Algesten, G., Sobek, S., Tranvik, L. and Jansson, M. (2004). Emission of CO2 from hydroelectric reservoirs in northern Sweden. - Archiv für Hydrobiologie 159:25-42.
• Brydsten, L.; Jansson, M.; Andersson, T., and Nilsson, Å. (1990). Element transport in regulated and non-regulated rivers in northern Sweden. - Regulated Rivers Research and Management 5:167-176.
• Callender, E. and Smith, R. A. (1993) Deposition of Organic Carbon in Upper Missouri River Reservoirs. - pp. 65-79. I: Kempe, S.; Eisma, D., and Degens, E. T. (eds.) Transport of Carbon and Nutrients in Lakes and Estuaries. Hamburg, FRG: Mitteilungen aus dem Geologisch-Paläontologischen Institut der Universität Hamburg; Part 6, 319 pp.(SCOPE/UNEP; v. Sonderband 74).
• Egerup, J. (2001) Vattenkraftens bidrag till emissioner av växthusgaser. Kalmar, Sweden: Högskolan i Kalmar; B.Sc.Thesis.
• Johansson, M. (1999) Turnover of organic matter in a hydroelectric reservoir - especially the carbon exchange between the atmosphere and the water. - Uppsala, Sweden: Uppsala University School of Engineering, Aquatic and Environmental Engineering; M.Sc.Thesis.
• St.Louis, V. L.; Kelly, C. A.; Duchemin, E.; Rudd, J. W. M., and Rosenberg, D. M. (2000 ). Reservoir Surfaces as Sources of Greenhouse Gases to the Atmosphere: A Global Estimate. - BioScience 50:766-775.
• Svensson, B. S. (2000) Greenhouse gas emissions from hydroelectric reservoirs - the need of a new appraisal. - Presentation made at the COP6 Conference, Den Hague, The Netherlands.
• Svensson, B. S.; Kyläkorpi, L., and Blümer, M. (1996). Vattenkraftens bidrag till växthuseffekten. - Pp. 21-32 I: Zuber, A. (secretary) Klimatdelegationens årsrapport 1996. Stockholm, Sweden: Delegationen för Klimatfrågor.