Carbon Capture and Storage involves the capture of the
CO2 produced from fossil
fuel combustion via chemical absorption and then release, with the gas being
compressed and pumped along pipes for storage in empty undersea oil and natural
gas wells or other geological strata. It is
sometimes claimed that CCS can reduce emissions from the use of fossil fuel by
80-89%, although in practice its overall
efficiency may be more like 60-70%, since the various
CCS processes use energy and supplying that adds more emissions. Coal CCS is
usually harder and more expensive than fossil gas CCS, partly because, to get
high efficiency, the coal has to be gasified as a first stage.
Permanent storage is obviously the ideal, but some
doubt whether it can be achieved reliably over very long periods, depending on
the location and its geology. Oil and
natural gas were trapped underground in strata safely for eons, so it is argued
that replacing them with compressed CO2 should
not involve extra risks. However, accidental rupture and rapid release of large
volumes of gas could be very dangerous, although some of the gas may, in time,
combine with rocks to form new solid calcium carbonate deposits. Some experience
with geological injection and storage has been gained from Enhanced Oil
Recovery using injected gas, although very long term storage would involve new challenges.
CCS has been seen a vital, with the IEA arguing that,
globally, ‘CCS could deliver 13% of the
cumulative emissions reductions needed by 2050 to limit the global increase in
temperature to 2°C (IEA 2DS). There was also some urgency,
with Oxford Prof. Myles
Allen arguing that ‘early investment in carbon dioxide disposal is crucial because most of
the cheapest options, like underground storage, will take decades to develop
and gain public acceptance’.
Biomass with Carbon Capture (BECCS) too has attracted interest, since it
would be carbon negative. The ETI has estimates
that BECCS could supply around 10% of UK power along with substantial net
carbon reduction, servicing around 10GW of power generation and other industrial sources
fitted with CCS. However, views differ on the need for
and viability of BECCS. Clearly its
progress depends on the success of CCS, as well as the development bioenergy
technology and the necessary sustainable sources- its wide scale use implies a
significant increase in biomass production.
Progress on CCS has been slow, with concerns about the cost leading the
UK to abandon its £1 billion CCS competition. That was seen by some as very unwise. However the slow
down was replicated elsewhere, with work on the flagship US Kemper coal CCS project being halted. Norway, already a CCS pioneer
with its enhanced oil recovery technology, has now cut its CCS funding. Some
project work continues, and there are some working projects like the Petra
Nova project in the USA. But the overall message seems
to be that for the moment it is ‘game
over’ for CCS in the EU especially. The UK Department of Business,
Energy and Industrial
Strategy projections in late 2017 had CCS at only 1GW installed in the UK by
2035, and that may be optimistic:
These
setbacks will not be welcomed by those who see CCS as the best way to secure a
future for fossil fuel, or by those who believe CCS and/or BECCS are vital to
reduce carbon emissions. Most recent energy scenarios have
included CCS as a key element, and some have included BECCS, although the
emphasis has varied. For example, while the IEA sees CCS as important for the
power and industrial sectors, and also backs BECCS, IRENA see CCS as being deployed exclusively in the industry
sector, with conventional renewables dominating.
Certainly CCS can be used for carbon emissions from industrial processes
as well as from power plants. It may be that, given the slow down in CCS
development, this will be the main focus, since, some argue, it offers an
easier way to decarbonise industrial activities, than replacing fossil fuel
with renewables. That is debatable: it depends of the industrial process, although, if, rather than CCS, carbon capture
and utilization is adopted (i.e. CCU)
then some industries may find it possible to develop new products and synfuels.
In general, CCU does look more attractive than CCS given that it offers the
potential for new valuable products and it may be that, unlike CCS, it will
prosper in some sectors. Though that is not clear- renewables may offer a better
overall decarbonisation outcome. That
also seems to be the case for the idea of air capture of CO2- a very long
shot, given that the proportion of CO2 in ait is much less than
that in power plant exhausts.
The prospects for BECCS, or indeed BECCU, are even
less clear. Those concerned about the environmental impact of the use
of biomass are inevitably unhappy with BECCS. They see it as having major land
use impacts and as undermining important carbon sinks. In
a report for Chatham House, Duncan Brack
says The
reliance on BECCS of so many of the climate mitigation scenarios reviewed by
the IPCC is of major concern,
potentially distracting attention from other mitigation options & encouraging
decision makers to lock themselves into high-carbon options in the short term
on the assumption that the emissions thus generated can
be compensated for in the long term.
Progress on the various carbon capture option discussed above is clearly
limited, with some greens welcoming
that: they see carbon capture as deflecting support from renewables. Some also similarly
see the current focus on fossil-derived hydrogen as in the H21 project
proposed for Leeds, as a diversion from
a switch to genuinely ‘green hydrogen’ produced using renewables sources (with
no need for CCS). Others however see this developments as a possible step on
the way to the adoption of renewable hydrogen, and as way to establish greener
gas in the heating market, ready for later replacement by fully green bio gas
and P2G syngas gas, when that becomes available on a wide scale.
It is important to defend renewables against diversions, but it is still
the case that fossil fuels remain the dominant suppliers, and they will be so
for some while. In which case, if carbon
emission reduction is seen as urgent, then clean-up options are also urgent, if
only perhaps as interim measures, while development of renewables proceeds -
all in the context of a diminishing reliance on fail fuels. But then we have to
decide which options to back! It’s
easier just to say no to them all! However, the issues have to be faced,
and in
a context where renewables are dominant and a diminishing reliance on fossil
fuel has been agreed, that may be less threatening.
A new book The Long Goodbye
on exiting from coal, out next year, explores these issue further. It’s also
interesting to see that the Global
Warming Policy Foundation has published a report by Prof. Gordon
Hughes which argued that CCS, coal CCS especially,
is expensive and ineffective. Indeed it says ‘for China, investment in
the transmission grid to permit wind generation in the west to be managed
jointly with hydro plants in the rest of the country is a far cheaper way of
reducing CO2 emissions in the next 10–15 years than retrofitting existing coal plants
with CCS or building new coal plants with CCS’. Not what you’d expect from
a GWPF report!
