Clearly, no private fossil fuel company will undertake CCS (apart from supplying small amounts for EOR etc) unless they are compelled to by a carbon tax on emissions, or given subsidies. Fossil fuel power stations not optimised for CCS (and few are) will have much higher energy and monetary costs for capture that those so optimised. There are also legal and other problems with the CO2 burial stage. Who will monitor for CO2 escape and for how long? Will citizens accept the burial of many billions of tonnes of CO2 (at present, a mere 10 million tonnes are sequestered annually), and the widespread increased pressures they will create? Finally, as we eventually move away from fossil fuels, the potential for CCS will fall, and net emissions technologies (such as direct air capture) will be the only means for lowering atmospheric CO2 levels, should this prove necessary.

Dear Pavel,

AS CO2 is a gas, its handling will be expensive and may render the energy gained from fossil fuel very reduced. So, i estimate the use of emissionless energy sources is more economical and this is what the people undertake now.

Best wishes

Dear Professor Moriarty,

Thank you very much for your reply. I fully agree that simple storage of CO2 (in the sub-seamed or saline formations) is a questionable decision for the reasons you mentioned.

Dear Professor Zekry,

I also agree that CCS usually loses to emissionless energy sources when we talk about energy generation. Despite the fact that the efficiency and cost of these sources, without significant government support, is still uncompetitive compared to natural gas or oil.

However, the interest in CCS technologies and their development prospects, as I think, can be connected with the possibility of obtaining a certain economic effect from EOR, ECBM and, probably, a number of other promising areas of CO2 use.

Maybe I'm wrong, but it seems to me that until the full transition to renewable energy, which will not happen soon, the issues of improving the efficiency of fossil fuel extraction will be relevant (including recovery factor). In this context, CCS-EOR/ECBM etc. can become a transitional technologies in the process of fossil energy generation abandonment. Transitional, because they partially solve two problems: improving the efficiency of fossil fuels extraction and reducing technogenic CO2 emissions.

In the long term, if we assume that there will be a complete abandonment of the fossil fuels use as energy sources, the infrastructure created by CCS could be used for the development of high-tech industries such as oil refining and gas processing. Perhaps this infrastructure could also find a different use within the framework of circular economics, but, with my point of view, this possibility is too long-term to be reliably predicted.

Yes Pavel,

Your arguments for CCS seems convincing to some extent. However, this requires to develop such infrastructure for carbon capturing. Before that one has to assess the the energy paid to capture one kilogram and compare it with the useful free energy from burning the quantity of fuel that released this quantity of carbon.

May be the question can one split CO2 to C and O2 what is the cost of this process. One can release oxygen and store carbon. May one use the solar energy in running this process.

Best wishes

CCS is not a well developed project yet. Leakage of carbon into the overlying strata from the placement of Carbon storage is the major concern until now. But numerous research are being undergone right now to solve this problem. US energy department have recently announced a 2.5 million dollar funded project in this purpose. If this can be established, then other prospects like EOR may turn into a new era.

An almost impossible question to answer in a few paragraphs, but here are some points to consider.

· CCS is being deployed at a number of locations around the world for EOR recovery, the oil displaced by the CO2 making the process economic. Regrettably, when the recovered oil is consumed it reduces the net reduction of CO2 emissions. To maximize the benefits of CCS, the CO2 has to be injected into a geological strata for permanent storage without EOR. Such a plant operating in isolation will not be economic. However, in a generating system that is endeavouring to reduce GHG emissions at minimum cost, CCS has a role to play.

· The appetite for energy is insatiable, both power and natural gas. Assuming this vast market could be replaced by renewable sources, there would have to be significant excess production capacity to cater for the intermittent nature of renewables. The installed capacity would have to serve the market under the worst conditions, low wind, heavy cloud cover, scheduled outages for repairs etc. Some estimate that the over build could be over 300 percent more than peak demand, which means for much of the time the resources are under utilized. This greatly increases the cost of energy to the consumer, despite wind and sun being free.

· Under these circumstances CCS could become a more economic option and is available at the flick of a switch. A fossil-fuelled power system requires less than 20 percent excess production capacity and even when coupled with CCS the cost of energy to the consumer is projected to be lower than for a system based solely on renewables.

· CCS plants would be used to remove CO2 from power plant flue gases or from natural gas steam reforming units allowing hydrogen to be used at source of use. The plants could be located at coastal sites allowing the CO2 to be injected into strata below the ocean obviating any risk to the population.

· There is likely a cost-of-energy minimum, satisfied by certain percentages of renewables and fossil plants with CCS (do not forget nuclear). Where is that sweet spot? And could it be exceeded by continued development of renewable sources with no corresponding construction of CCS?

· Research into improved technologies is in progress and likely to lower the cost of CO2 capture. For example, a solvent that could be regenerated at lower temperature and higher pressure would greatly reduce thermal and compression energy losses. However, do we have time to wait for these improved technologies? The indications are that we do not.

· There is a lot of meaningful discussion but unless a serious commitment is made to reduce GHG emissions, CCS is likely to remain a viable solution in waiting.

Difficult question. There are many technical and financial issues - with others in this conversation have intelligently identified. I am keen to point out two things:

a) with a CO2 emissions tax in Norway (for over 25 years), real industrial-scale CCS project can be realized (there are also similar projects in e.g. Canada and USA)

b) Do humans really want to use valuable hydrocarbon chains without emitting the CO2 molecules to atmosphere?

There are two simple answers to (b) either "No - stop using fossil fuels" or "yes - so lets use CCS"

The Australian government smoked $2b a few years ago through various large scale demonstration projects looking for an answer and came up with a negative one! The geological requirements for CO2 storage itself rules out vast majority of the sites and building long pipes adds to an already high cost. The low cost of alternatives especially with the low oil prices of recent years and falling cost of solar/wind put a dampener on it. There are still demonstration and pilot projects happening in various parts of the world: https://www.iea.org/tcep/industry/ccs/

Looking ahead though it has to be an integral part of the CO2 reduction IF we are serious about climate change. IEA has categorically stated CCS being part of the solution. It however is a big IF and life after Paris has not changed that much. It will take a bold policy intervention like a high carbon tax. India and China would have to that party and they are both focusing on renewables of several hundred GW in each country over the next few years. This won't leave much headroom for investment in CCS. In fact, the investment paradigm in CCS is going to be quite complicated with enabling public investment in the storage part being critical. I go back to the point that even several hundred GWs of renewables is not going to cut it for meeting the emissions reduction target in these two countries. It has been stated in several studies most notably by IEA and the Global CCS Institute (https://www.globalccsinstitute.com/).

Let us hope CCS makes a comeback at some stage.

Dr Chattopadhyay, You may wish (along with any other readers) contribute to the Question on RG, "By what, and how, would fossil fuels for power generation, heating, anf motive power be replaced?" In particular, if CCS is not used in conjunction with fossil fuels what technologies are available in the short-term to satisfy the world's mammoth energy needs?