Carbon Capture and Storage: Options, Techniques, and Considerations

1. Energy and the New Reality, Volume 2:C-Free Energy SupplyChapter 9: Carbon capture and storage L. D. Danny Harveyharvey@geog.utoronto.ca Publisher: Earthscan, UKHomepage: www.earthscan.co.uk/?tabid=101808 This material is intended for use in lectures, presentations and as handouts to students, and is provided in Powerpoint format so as to allow customization for the individual needs of course instructors. Permission of the author and publisher is required for any other usage. Please see www.earthscan.co.uk for contact details.

2. Sequence of options:Capture and burial of CO2 from: • Coal powerplants - why bother? • Natural gas powerplants – if still used to complement wind and solar • Concentrated industrial sources that are hard to displace otherwise • Biomass combustion – to create negative emissions • The atmosphere – after emissions have been eliminated, to begin drawing down atmospheric CO2 • The atmosphere, and combined with H2 produced electrolytically from renewable electricity to make synthetic “natural” gas – to use in the existing natural gas distribution network for heating of buildings

3. Outline • Sources of CO2 for capture • Capture techniques • Energy penalties • Compression or liquefaction • Disposal sites • Environmental, safety and legal issues • Timing • Strategic considerations

4. Context:In many scenarios of how fossil fuel CO2 emissions might be eliminated this century, heavy reliance is placed on shifting transportation and heating to electricity combined with C capture and storage - essentially allowing substantial continuation of fossil fuels (along with substantial renewable and nuclear energy and some efficiency improvements in the use of energy to reduce demand)

5. Definitions: • Carbon Capture and Storage (CCS) refers to the capture and disposal of CO2 released from industrial processes • This has also been referred to as Carbon Sequestration, but this term has also been applied to the removal of CO2 from the atmosphere through the buildup of biomass (above-ground vegetation) and/or soil carbon • CCS involving burial of captured CO2 in geological strata (either on land or under the sea bed), shall be referred to here as geological carbon sequestration, while buildup of soil or plant C shall be referred to as biological carbon sequestration

6. CO2 is easiest to capture when both the concentration and absolute partial pressure are large

7. Table 9.1 Properties of gas streams Source: Gale et al (2005, ‘Sources of CO2’, in IPCC Special Report on Carbon Dioxide Capture and Storage, Cambridge University Press, Cambridge, UK)

8. Figure 9.1 A chemical solvent-based plant that captures a mere 200 tCO2/day Source: Thambimuthu et al (2005, IPCC Special Report on Carbon Dioxide Capture and Storage, Cambridge University Press, Cambridge, UK)

9. All of the stationary CO2 sources worldwide of 0.1 MtCO2/yr or more account for about 54% of total world CO2 emissions (see Table 9.2)

10. Options for capture of CO2 from fossil fuel powerplants: • From the flue gases after normal combustion of fuel in air • From the flue gases after combustion of fuel in pure oxygen (oxyfuel methods in Table 9.3) • Prior to combustion, during the gasification of coal for IGCC (Integrated gasification-combined cycle) powerplants • During the operation of fuel cells using fossil fuels

11. Processes for separating CO2 from other gases (applicable to capture after combustion in air or during gasification) • Absorption - chemical (if low CO2 concentration) (MEA is a common solvent) - physical (if high CO2 concentration) (Selexol is a common solvent) • Adsorption • Membrane-based separation • Liquefaction

12. Energy is required • Chemical solvents require heat to drive off the CO2 (in concentrated form) and regenerate the solvent • Physical solvents require heat or a pressure drop for regeneration • Adsorbants require heat or a pressure drop for regeneration • Membrane systems require electrical energy to maintain a high P on one side of the membrane • Liquefaction requires cooling the exhaust gas to as low as ~ 220 K

13. Combustion in oxygen • The only gases produced are CO2 and water vapour • Pure CO2 is produced by cooling the gas enough to condense out the water vapour (giving 96% CO2) followed by distillation if desired • Energy is required to separate O2 from air in liquid form (usually by cooling the air to 89 K, at which point O2 condenses as a liquid)

14. IGCC (Integrated Gasification-Combined Cycle) for coal powerplants • Involves converting the coal to CO2, CO, and H2 by heating it in 95% oxygen • The CO can be reacted with steam to produce more CO2 and H2 • The resulting stream is almost completely CO2 and H2, and the CO2 is easily removed prior to combustion of the H2 • Conversely, CO and H2 can be fed to the turbine, burned in air, and the CO2 removed after combustion using a chemical solvent • Finally, CO and H2 can be fed to the turbine, burned in pure O2, and the CO2 separated by condensing the water vapour that is produced from combustion of the H2

15. All methods of CO2 capture involve an energy penalty • Capture after combustion in air requires either a physical or chemical solvent that absorbs the CO2 but which needs to be regenerated using heat, or uses membranes but requires ~ 15% of the powerplant output to create high pressures • Capture after combustion in oxygen is easy (only H2O and CO2 are produced), but energy is required to separate oxygen from air (cryogenically) • Capture during gasification of coal or during operation of fuel cells entails a very small penalty (a few % at most)

16. Efficiency Penalties & Costs

17. Costs, fraction of CO2 captured, and efficiencies in generating electricity with and with C capture Source: Rubin et al. (2015, Int. J GHG control 40:378-400)

18. Taking advance coal powerplants as an example • the efficiency in generating electricity is 42% without CO2 capture, and 32% with CO2 capture • Since the amount of coal needed to generate a unit of electricity varies with 1/efficiency, the ratio of coal use (with capture/without capture) is 42/32=1.31 • Thus, 31% more coal is needed with CO2 capture compared to without

19. Cost and capacity factor (CF) comparisons • Coal: $2500-4000/kW without C capture $4000-5000/kW with C capture • Onshore wind: $1000-1600/kW, 15-25% CF • Offshore wind: $2000-5000/kW, 25-50% CF • Floating offshore wind: $4000-5000/kW • PV: $2000-4000/kW (today), 15-25% CF • CSTP: $3000-9000/kW today • $2000-3000/kW future, 25-85% CF

20. Effective CO2 Capture FractionBecause of the efficiency penalty, more fuel is needed to produce the same amount of electricity, and the effective CO2 capture fraction is reducedFor example, if 80% of the CO2 in the exhaust is captured but the efficiency of the powerplant drops from 40% to 35%, then 40/35=1.143 times as much fuel is required. The CO2 emission is thus 0.2 x 1.143 = 0.229, so the effective capture fraction is only 77.1% (1.0-0.229)

21. Pilot Projects: A proposed 450-MW IGCC powerplant with carbon capture in Saskatchewan was abandoned after estimated costs ballooned from Cdn$3778/kW to Cdn$8444/kW.The US DOE FutureGen project (a 275-MW IGCC plant that would co-produce electricity and hydrogen) was cancelled around 2007 after projected costs rose from $3250/kW to $6500/kW (Obama re-instated the project).

22. At COP24 (the 24th meeting of the Conference of Parties to the UN Climate Change Convention), in Bonn in November 2017, 23 governments and additional businesses, lead by Canada and the UK, formed the “Powering Past Coal Coalition” and agreed to the following:“Government partners commit to phasing out existing traditional coal power and placing a moratorium on any new traditional coal power stations without operational carbon capture and storage, within our jurisdictions.Business and other non-government partners commit to powering their operations without coal.All partners commit to supporting clean power through their policies (whether public or corporate, as appropriate) and investments and restricting financing for traditional coal power stations without operational carbon capture and storage.”

23. The governments involved are:Alberta, Angola, AustriaBelgium, British ColumbiaCanada, Costa RicaDenmark, El SalvadorFiji, Finland, France Italy, LuxembourgMarshall Islands, Mexico Netherlands, New ZealandNiue, Ontario, Oregon Portugal, QuébecSwitzerland, United Kingdom Vancouver, Washington

24. Note that the declaration bans coal unless it has CCS – but even without CCS, coal powerplants are now more expensive than onshore wind and PV, and not much less expensive than offshore wind and CSTP. With CCS, coal powerplants are even more expensive. So, effectively, this means an end of coal for electricity among the participating countries. The hope was expressed by the original partners that, by COP25 (in 2018), 50 partners will have signed on.

25. Use of biomass with CCS to create negative CO2 emissions

26. BECCS – Biomass Energy-Carbon Capture and Storage Source: Kemper (2015, Int J. GHG Control 40:401-430)

27. Capturing CO2 from biomass powerplants The most efficient method of producing electricity from biomass is through biomass integrated gasification combined cycle (BIGCC), a technology that is still under developmentGasification of biomass would occur in pure O2, producing syngas (a mixture of CH4, CO2, CO and H2) and a char residue that is combusted to provide heat for the gasification process.

28. The syngas would be used in a gas turbine to generate electricity, with waste heat from the gas turbine used to produce steam for use in a steam turbine to generate further electricity (as in natural gas combined-cycle power plants, NGCC)NGCC state-of-the art powerplants have an efficiency of 55-60%BIGCC efficiency would be after 34% without capture of CO2 and only 25% with capture of CO2The result is an effective CO2 capture fraction of only 39% and an increase in the required biomass by 33%

29. C Flow for a dedicated switchgrass-IGCC powerplant Source: Kemper (2015, Int J. GHG Control 40:401-430)

30. Table 9.6Characteristics of capture of CO2 from BIGCC powerplants (with or without the water shift reaction) that could be available after 10 years of intensive R & D Source: Rhodes and Keith (2005, Biomass and Bioenergy 29, 440–450

31. Various schemes for capturing CO2 that would be produced from gasification of black liquor (a processing waste) in integrated pulp and paper appear to be much more favourable, but would also require many years of intensive research and development

32. Status of BECCS projects in 2014 Source: Kemper (2015, Int J. GHG Control 40:401-430)

33. Capture of CO2 during the production of N fertilizer • Production of ammonium nitrate from natural gas or coal releases CO2 chemically, in addition to the CO2 released through the combustion of fuels in order to provide heat for the chemical reaction 3CH4 + 4N2 + 2H2O + 8O2→ 4NH4NO3 + 3CO2 ↑ • Production of ammonium bicarbonate consumes CO2 chemically, offsetting (at least in part) the CO2 produced from combustion of fuels to supply heat for the reaction 3CH4 + 4N2 + 14H2O + 5CO2→ 8NH4HCO3 ↓

34. Conversely, flue gases from combustion of fossil fuels or biomass could be used as a source of C for the production of ammonium bicarbonate through the net reaction2CO2 + N2 +3H2 + 2H2O → 2NH4HCO3↓with the H2 produced electrolytically from water using renewable energy to generate the electricity used for electrolysis. 90% of CO2 in flue gases would be taken up by the above net reaction.

35. Direct Air Capture (DAC) of CO2This entails flow of ambient air over a chemical sorbent that selectively removes CO2, then releasing the captured CO2 in concentrated form for collection and disposal, and regeneration of the sorbent

36. Capture of CO2 from ambient airOne direct capture scheme involves the following steps: • Absorption of CO2 by NaOH solution, producing dissolved Na2CO3 • Reaction with Na2CO3 with Ca(OH)2 to produce CaCO3 and NaOH • Decomposition of CaCO3 to CaO (lime) and CO2 • Reaction of CaO with H2O to regenerate Ca(OH)2

37. According to a 2011 assessment of DAC: • The cost is estimated to be $600/tCO2, with large uncertainty and higher values more likely than lower values • No demonstration or pilot-scale DAC system had been deployed anywhere • It is entirely possible that no DAC concept under discussion today or yet to be invented will succeed in practice

38. An enormous physical structure would be required to remove even modest amounts of CO2 from the atmosphere • To remove CO2 from the atmosphere at a rate equivalent to the emission from one 1000-MW (1-GW) coal power plant would require a structure 10m high and 30 km long (this would absorb 6 MtCO2/yr). • Lots of electricity would be need to power fans to such air over the absorbing surfaces, and heat would be used to regenerate the absorbing materials • This could be powered by renewable energy, but it would make sense to do this only after all existing electricity emission sources have been replaced with renewable energy sources.

39. Perspective: • Pre-industrial atmospheric CO2 concentration was 280 ppmv • The current concentration is 400 ppmv • Under aggressive emission-reduction scenarios, the concentration peaks at 450-500 ppmv • To draw down the concentration by 50 ppmv means lowering the amount of CO2 in the atmosphere by roughly 100 Gt • But once we start removing CO2, the biosphere and oceanic CO2 sinks get weaker, so to have a sustained lowering by 100 Gt means removing about 200 GtC or 733 GtCO2 or 733,000 Mt CO2 • If done over a period of 100 years, this means removing about 7300 Mt CO2/yr – with about 1200 structures 10 m x 30 km.

40. Compression or liquefaction of captured CO2

41. Compression of CO2 • Compression would be required prior to transport by pipeline, with an energy requirement of 300-400 kWh/tC if compressed from 1.3 to 110 atm • If applied to all of the CO2 produced by a coal powerplant with 40% efficiency, this corresponds to an energy cost of 7-10% of the electricity produced (this is in addition to the energy required to capture the CO2 from the flue gases)

42. Liquefaction of CO2 • Liquefaction would be required prior to transport by ship, with an energy requirement of about 400-440 kWh/tC. • The latter would amount to an efficiency penalty of 10-12% if applied to the CO2 produced from a coal powerplant, but less than 2% if applied to the 71% of the CO2 that can be easily captured while producing H2 from natural gas

43. Disposal sites: • Deep saline aquifers on land and beneath the ocean bed • Depleted oil and gas fields • Active oil fields, as part of enhanced oil recovery • Coal beds (displacing coal-bed methane) • Injection below the 3000 m depth in the ocean (liquid CO2 is denser than seawater at this and greater depths)

44. Storage of CO2 in deep saline aquifers • Some remains as a gas, under pressure • Some dissolves very slowly into pore water • In aquifers rich in calcium and magnesium silicates, the CO2 will react with the rock and carbonate will precipitate, reducing the permeability of the rock and creating a permanent trap where none existed before – flood basalts are particularly good

45. Existing and planned aquifer storage projects: • Sleipner West gas field, underneath the North Sea (off of Norway) • Deep aquifers in Japan and US, planned for Australia, Germany, and Norway

46. Storage of CO2 in depleted oil and gas fields and for enhanced oil and gas recovery • CO2 is currently injected into the base of oil and gas fields in order to increase the oil or gas pressure, thereby increasing the amount of oil or gas that can be extracted • Only the net CO2 storage should count as credits against emissions • Storage in already-depleted oil and gas fields is another possibility, but would provide no economic credits and, like enhanced oil or gas recovery, would require long-distance transport of CO2 from the major emission regions to the major oil and gas fields

47. Storage of CO2 in coal beds • Coal usually contains methane that is adsorbed onto the surfaces of micro-pores • This methane is call coal-bed methane, and there can be up to 0.76 GJ methane/tonne of coal (compared to a heating value of coal itself of 32 GJ/t) • CO2 has a greater affinity for coal, so injection of CO2 into coal beds will displace methane while being stored in the coal • Up to 2 CO2 molecules are adsorbed for every CH4 molecule displaced • The methane would be collected and used as an energy source

48. Estimated Worldwide Storage Potential on Land • Oil and gas reservoirs: 230 GtC • Deep saline aquifers: 55-15,000 GtC, likely minimum: 270 GtC • Coal beds, 16-54 GtC theoretical potential, 2 GtC practical potential • TOTAL MINIMUM: about 500 GtC, equal to about 100 years of current fossil fuel emissions (about 10 GtC/yr) if storing the one half of current fossil fuel emissions that would be amenable to capture

49. Environmental and Safety Issues Associated with Capture, Transmission and Storage of CO2

50. Capture of CO2 • Emissions during production and transport of materials used for capture of CO2 (chemical or physical solvents, limestone and ammonia) • Transport and processing of waste produced during regeneration of solvents • Additional requirements for ammonia, limestone and water compared to generation of electricity without CO2 capture • Increased NOx and ammonia emissions from pulverized-coal powerplants with CO2 capture