Carbon capture and storage (CCS) involves capturing carbon dioxide released by power stations and other industrial sources, and burying it deep underground. In addition to keeping anthropogenic CO2 out of the atmosphere, this technology will lead to benefits and trade-offs for air pollution, according to a new report from the European Environment Agency (EEA). The report shows that while CCS may have an overall positive effect on air pollution, emissions of some pollutants may increase.
CCS technologies require approximately 15–25% more energy depending on the particular type of technology used, so plants with CCS need more fuel than conventional plants. This in turn can lead to increased direct emissions occurring from facilities where CCS is installed, and increased indirect emissions caused by the extraction and transport of the additional fuel.
The EEA report identifies some of the potential benefits and trade-offs for the main air pollutants. It also presents a life-cycle case study for 2050 considering three different scenarios, showing the potential impacts on emissions of air pollutants if CCS were widely implemented in Europe. Key findings include:
Sulphur dioxide (SO2) emissions from power plants are predicted to fall when carbon dioxide (CO2) is captured, as SO2 must also be removed after the fuel combustion stage for technical reasons. Although the extraction and transportation of additional coal will lead to higher SO2 emissions from these stages of the CCS life-cycle, SO2 emissions should decrease overall.
Particulate matter (PM) and nitrogen oxide (NOx) emissions are expected to increase in line with the amount of the additional fuel consumed if no additional measures to reduce emissions are installed.
Ammonia (NH3) is the only pollutant for which a significant increase in emissions is expected to occur, with emissions potentially increasing by a factor of 3 or more. The foreseen increase is due to the degradation of the amine-based solvents used to capture the CO2. However, in absolute terms the increase is small compared to existing ammonia emissions in Europe, 94% of which comes from agriculture. Ammonia contributes to acidification and eutrophication of the environment and also can form harmful fine particulate matter when released in the atmosphere.
Potential carbon dioxide (CO2) savings from CCS vary greatly across the three scenarios in the report. Emissions of CO2 in the EU would fall by around 60% by 2050 if CCS were implemented at all coal-based power generation plants. Implementing CCS at all coal, gas and biomass plants would result in net negative emissions—in effect removing CO2 from the atmosphere. This assumes that all biomass is harvested sustainably without any net changes to the carbon stock.
The case study also shows clearly that the extraction and transport of additional coal can contribute significantly to the life-cycle emissions for coal-based CO2 capture technologies. Overall, however, CCS is considered to be generally beneficial both in terms of climate change and air pollution. However, the potential increase in certain pollutants such as NH3, NOx and PM is important.
In the EU, there are plans to build several demonstration plants for CO2 capture and storage in order to commercialise the technology from 2020. Currently, there are around 80 large scale CCS projects at various stages of development around the world but only a few are operational. There are as yet no large-scale CCS plants in operation which cover all three elements of the CCS chain—the capture, transport and storage of CO2.