Institute for Sustainability

Impact of carbon capture & storage on water

Impact of carbon capture & storage on water

Coal, gas and nuclear power stations often use water intensively, as it is needed for producing and cooling steam to generate electricity.

To mitigate climate change, carbon capture and storage (CCS) has been proposed as a solution to reduce emissions from coal and gas power stations.

The purpose of CCS is to sequester carbon emissions from coal or gas fired power stations in a safe and secure way, but it will put further pressure on water resources.

Research led by Dr Edward Byers, who completed his PhD at the School of Engineering and Geosciences, has modelled different energy pathways based on the UK government’s roadmap for CCS deployment. The work includes examining the impact of CCS on large river basins such as the River Trent. Researchers modelled future use of water for cooling thermoelectric power stations under a medium emissions climate scenario.

“A warming climate is expected to bring reduced run-off, water availability and drought to the UK, yet the pressure to decarbonise the electricity system may lead to greater water intensity of electricity production”, says Dr Byers.

Based on the scenarios modelled by researchers, the highest concentration of CCS power plants is likely to be in the Yorkshire/Humber area and the North West.  These regions are closest to the North and Irish Sea oil fields where CO2 is expected to be sequestered. To do this in an efficient and cost-effective way, CCS power stations would be clustered together.

Drax power station

Carbon capture and storage uses more water

CCS is expected to play a role in the electricity sector to help reduce greenhouse gas emissions by 80% on 1990 levels by 2050. The sector currently accounts for 34% of emissions in the UK.

The catch is that water intensity almost doubles when CCS is installed to capture emissions from coal power plants, meaning cooling demands can be 26 to 140% higher according to the research.

“We need to pay attention to how water resources are managed in those regions where we expect to have high levels of CCS as it will have levels of freshwater use that perhaps will be double by the year 2050."

CCS also makes thermoelectric power stations less efficient as it adds an extra load that needs to be supplied by the power stations.

Unless something is done to reduce CCS’s demand for more water, it will increase water usage by coal power stations pushing rivers beyond what they are capable of supplying for the thirsty power plants.  

River Trent

How to reduce water demands for CCS

As water resources become scarce in the future, mainly due to environmental pressures from economic growth, rising population and climate change, there will be less water available for thermoelectric power generation.

Already thermoelectric power stations use approximately 5% of available freshwater resources in England and Wales. In the U.S and some European countries, the figure may be much higher, in the region of 30-40%.

Fortunately, there are ways to reduce water demands for CCS power stations that could be used:

  • ‘Closed loop’ cooling systems that re-use cooling water in a second cycle rather than discharging it back to the source the first time, which reduces the amount of water for cooling, but consumes more of it.
  • Switching to hybrid cooling systems that use both water and air could reduce water use by 15-35%. Dry air cooling is also an option, but increases costs even further.
  • Shift generating capacity to either estuaries or the coast, thus using non-freshwater sources for cooling.

Risks of coastline power stations

Power stations located along the coastline, including nuclear, risk damaging aquatic habitats.

“Increasing emissions of thermal discharge brings additional negative environmental and ecological impacts which need to be taken into consideration alongside other benefits of nuclear power. This is not beyond current expertise, but requires additional attention.”

They may also be more vulnerable to storms and coastal flooding. 

Key points to consider for CCS power stations:

  • In regions with high demands from CCS, water demands may exceed availability in rivers during very low flows.
  • Gas fired power stations use less water than coal stations, even with CCS.
  • CCS coal power stations located on rivers with low flows will have twice the impact on water consumption and downstream impacts than a similar gas turbine power station.
  • Less water is used by power stations if hybrid and dry cooling configurations are used instead.
  • Energy pathways with more coal CCS will be more water intensive than current levels.
  • Freshwater consumption increases with the level of capacity for CCS coal power stations

Publications

Byers E, Qadrdan M, Leathard A, Alderson D, Hall JW, Amezaga JM, Tran M, Kilsby CG, Chaudry M. (2015) Cooling water for Britain's future electricity supply. Proceedings of the ICE – Energy doi:10.1680/ener.14.00028

Byers E, Hall JW, Amezaga JM. (2014) Electricity generation and cooling water use: UK pathways to 2050Global Environmental Change, 25, 16–30 doi:10.1016/j.gloenvcha.2014.01.005