Nuclear has a larger carbon footprint than either hydro or wind power according to a report prepared for the UK Parliament, see, "The Carbon Footprint of Electrical Power Generation", http://www.parliament.uk/documents/upload/...

Hydro Hydropower converts the energy from flowing water, via turbines and generators, into electricity. There are two main types of hydroelectric schemes; storage and run-of-river. Storage schemes require dams. In run-of-river schemes, turbines are placed in the natural flow of ariver. Once in operation, hydro schemes emit very little CO2, although some methane emissions do arise due to decomposition of flooded vegetation. Storage schemes have a higher footprint, (10-30gCO2eq/kWh), than run-of-river schemes as they require large amounts of raw materials (steel and concrete) to construct the dam.9Run-of-river schemes have very small reservoirs (those with weirs) or none at all so do not give rise to significant emissions during their operation. Carbon footprints for this type of hydro scheme are some of the lowest of all electricity generation technologies (<5gCO2eq/kWh).

Wind Electricity generated from wind energy has one of the lowest carbon footprints. As with other low carbon technologies, nearly all the emissions occur during the manufacturing and construction phases, arising from the production of steel for the tower, concrete for the foundations and epoxy/fibreglass for the rotor blades.10These account for 98% of the total life cycle CO2emissions. Emissions generated during operation of wind turbines arise from routine maintenance inspection trips. This includes use of lubricants and transport. Onshore wind turbines are accessed by vehicle, while offshore turbines are maintained using boats and helicopters. The manufacturing process for both onshore and offshore wind plant is very similar, so life cycle assessment shows that there is little difference between the carbon footprint of onshore (4.64gCO2eq/kWh) versus offshore (5.25gCO2eq/kWh) wind generation (Fig 2).11 The footprint of an offshore turbine is marginally greater because it requires larger foundations.

Nuclear Nuclear power generation has a relatively small carbon footprint (5gCO2eq/kWh) (Fig 2). Since there is no combustion, (heat is generated by fission of uranium or plutonium), operational CO2emissions account for <1% of the total. Most emissions occur during uranium mining, enrichment and fuel fabrication. Decommissioning accounts for 35% of the lifetime CO2emissions, and includes emissions arising from dismantling the nuclear plant and the construction and maintenance of waste storage facilities.12The most energy intensive phase of the nuclear cycle is uranium extraction, which accounts for 40% of the total CO2emissions. Some commentators have suggested that if global nuclear generation capacityincreases, higher grade uranium ore deposits would be depleted, requiring use of lower grade ores. This has raised concerns that the carbon footprint of nuclear generation may increase in the future (see Issues)

Mark