Published: Nov 17, 2011
Last modified: Nov 22, 2011
Carbon capture and storage (CCS) involves
capturing carbon dioxide released by
power stations and other industrial sources,
and burying it deep underground. But in
addition to keeping an important greenhouse
gas (GHG) out of the atmosphere, this technology
will lead to benefits and trade-offs for
air pollution. A new report from the European
Environment Agency (EEA) describes the effects
that CCS may have on emissions of some key
air pollutants.
Carbon capture and
storage can bridge the gap for the next
few decades, cutting emissions until we
can shift to a low carbon economy. Our report
shows that while CCS may have an overall
positive effect on air pollution, emissions
of some pollutants may increase. Understanding
these types of trade-offs are extremely
important if we are to deploy this technology
across Europe and the world.
"Carbon capture
and storage can bridge the gap for the next
few decades, cutting emissions until we
can shift to a low carbon economy",
Professor Jacqueline McGlade EEA Executive
Director said. "Our report shows that
while CCS may have an overall positive effect
on air pollution, emissions of some pollutants
may increase. Understanding these types
of trade-offs are extremely important if
we are to deploy this technology across
Europe and the world."
What does CCS mean for air pollutants?
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.
Carbon capture and storage
technologies are assumed to play a central
role in helping Europe achieve its long-term
GHG reduction objectives in a cost-effective
way, reducing domestic GHG emissions by
80-95 % by 2050. Implementing CCS is therefore
considered as a bridging technology, and
should not introduce barriers or delays
to the EU’s objectives of moving toward
a lower-energy and more resource-efficient
economy.
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.
