2050 Pathways Analysis: Geo-sequestration levels
Besides BECCS, geo-sequestration could become an additional driver of negative emissions for the UK. Also referred to as carbon dioxide removal techniques, geosequestration aims to reduce the amount of greenhouse gases in the atmosphere via, for instance, engineered air capture technologies or enhanced weathering processes. The geo-sequestration levels presented in the 2050 Pathways Calculator describe a gradual build-up of mostly engineered air capture technologies. Levels 2 and 3 assess the negative emissions potential of these techniques within the boundaries of the UK. The most ambitious geo-sequestration activity is described in level 4. This entails the UK participating in an international initiative to deploy air capture technologies anywhere in the world wherever they are most effective. All negative emissions technologies can take advantage of the fact that CO2 travels freely in the atmosphere. The technologies can be installed wherever it is the most practical to do so. Level 4 maximises this strategic advantage.
We have two cost estimates, one for domestic and one for international geosequestration activities. No geosequestration technologies have yet been demostrated at the scale the 2050 sector levels are envisaging. Thus, cost estimates are unproven and further input into the analysis is much appreciated.
Level 1: As a baseline, level 1 assumes that no action on geo-sequestration is taken over the coming decades. Any geo-sequestration options that do emerge prove to be technologically unfeasible, financially unattractive, unacceptable to the public and/or insignificant in terms of their contribution to mitigation.
Costing level 1:
£0 - as there is no effort.
Level 2 Level 2 on geo-sequestration assumes the UK generates 1MtCO2 per year of negative emissions. These would be generated by business opportunities either in the form of biochar being linked to financial incentive structures or some business opportunities linked to negative emissions, such as the production of chalk or bio cement.
Costing level 2:
This trajectory presumes a 0.1MtCO2 per year in 2025 and then a gradual built-up of carbon sequestration to 1MtCO2 per year in 2050.
Case study for Carbon Cycle ltd 'induced air flow towers' process:
Indicative numbers partly informed by Carbon Trust report March 2011 on Carbon Cycle ltd process:
|•||Each of the 64 units would be 14m long, 4m high and 3m wide.|
|•||A one-third slice of the demostration units costs today to the tune of £30k (around 30% of the cost). Thus, one whole unit would cost around £100 000. Thus, 64 units would cost to the tune of £6m|
|•||Together the 64 units would process around 50kt of gypsum, removing 13kt (0.013Mt) of carbon dioxide from the atmosphere and produce 30kt of calcium carbonate and 40kt of ammonium sulphate annually.|
|•||These outputs are based on a 340 day operating year across the entire plant, i.e. 7% downtime for planned and unplanned maintenance.|
|•||‘With a spreadsheet analysis, the core process is extremely profitable with gross margins of over 50%, which is significantly more than achieved in other chemical industries. Once Carbon Cycle has a better understanding of how its process operates at a 1/20th scale, the spreadsheet needs to be updated and stress-tested.’ states the Carbon Trust|
Based on these assumptions:
A 0.1MtCO2 per year in 2025 would entail around 8 plants of 64 Carbon Cycle units. This would entail:
|•||Capital cost: 8 x £6m = £48m (estimating a 20 year lifespan that would be £2,5mio per year)|
|•||Fuel cost: 3.3 TWh per year per t/CO2 – thus, 0.33TWh per year in 2050.|
A 1MtCO2 per year in 2050 would entail around 80 plants of 64 Carbon Cycle units. This would entail:
|•||Capital cost: 80 x £6m = £480m (estimating a 20 year lifespan that would be £25mio per year)|
|•||Operating cost: 80 x 51kt = 4,080kt of gypsum; around 4000 workers to run (?!)|
|•||Fuel cost: 3.3 TWh per year per t/CO2|
To note: Carbon Trust assumes this process could be ‘highly profitable’. This, however, is not factored into the analysis. Also, above calculations do not take account of possible economies of scale as they refer to the upper high range of cost assumptions. The low range presumes costs of the technology will fall in 2050 to 10% of the 2010 cost level. Economies of scale would gradually force down prices to this level (this assumption is also being used for the low ranges in other geosequestration technologies, for instance for Klaus Lackner's mechanical air capture machines.)
Other options, which could add to a mix of geosequestration activities under this level, include:
|•||'Negative carbon' construction materials|
Further understanding of how much a 1 MtCO2 per annum capture rate would cost in the UK for these and other negative emission options would be much appreciated.
Level 3 assumes the construction of engineered air capture technologies within the UK geographical boundaries. A ten year demonstration phase would lead to a gradual build-up of engineered air capture technologies starting in 2025. Some engineered negative emissions technologies currently in R&D stage could possibly be deployed in the UK. Options include ‘forced draft contactors’ and ‘induced air flow towers’. As an example, each induced air flow tower, approximately 20 meters tall, is expected to capture 4tCO2 per day. Thus, induced air flow towers capturing 30 MtCO2 per year in 2050 would necessitate the operation of roughly 20,000 towers.
All the engineered air capture methods are presumed to necessitate CCS infrastructure and locations close to power stations as well as significant energy supplies. Level 3 assumes an engineered air capture technology contribution of 30 MtCO2 per year in 2050 with an energy demand of 100 TWh per year. The possibility of utilising excess heat from power stations as well as probable efficiency gains could reduce this energy demand.
Costing level 3:
When considering the Carbon Cycle 'induced air flow towers' process these amounts of 30 MtCO2 captured per year in 2050 could only be achieved if one considers the 'full-cylce' approach (this does not generate chalk as an end product, but separates the carbon dioxide ready for storage). We do not have cost estimates for this 'full cycle' process, thus, need to present some very rough figures. Believing there are no economies of scale and capital cost would be the same as for the 'one-way' process, we would just times by 30 the costs of level 2 plus capital as well as operational CCS costs. Under low cost assumptoins economies of scale are presumed to push down prices to 10% of today's. Thus
|•||Capital cost: 80 x £6m x 30/10 = £1.440mio (estimating a 20 year lifespan that would be £72 mio per year). Plus CCS capital cost ranges as described in the CCS chapter.|
|• Operation costs: CCS operation costs as outlined in CCS chapter.|
|•||Fuel cost: 33 TWh per year per t/CO2|
Level 4 assumes as in level 3 that the UK constructs its own air capture infrastructure in the 2020s, but also participates in an international negative emissions initiative. With international partners the UK would push for a global negative emissions effort to assist a worldwide mitigation strategy. Negative emission technologies would be deployed anywhere in the world wherever they are most cost effective. The UK holds a certain percentage share of negative emissions and counts them towards national mitigation targets. This level assumes that such an operation is in demonstration phase in 2020 with roll-out starting in 2030. It estimates that by 2050 the contribution of this negative emissions approach will deliver around 80 MtCO2 per year to the UK’s mitigation effort. It is also assumed that the energy cost of concentrating and compressing CO2 from the air is in line with statements of some experts in the field.
These energy demand projections are significantly lower than the ones used in level 3. For 80 MtCO2 captured per year the technologies listed below estimate an energy cost of between 40 TWh to 130 TWh per year.
All engineered negative emissions proposals would need to be investigated as to their suitability for deployment in specific regions of the world, their efficiency at capturing and storing CO2 and their impact on the environment. It is impossible to state which technology will ultimately be chosen following a decade-long demonstration phase.
Some contenders could include:
? Artificial ‘carbon trees’ that capture CO2 via an ion exchange resin. The resin absorbs CO2, which is released when exposed to water vapour. 405 The technology must be deployed in regions with a lot of dry air, with access to water and with a CCS capability. Possible locations are Canada, Africa or the Middle East. The container sized carbon trees are predicted to capture around 1 tCO2 per day. 80 MtCO2 per year would necessitate approximately 250,000 ‘carbon trees’.
? ‘Solar scrubber’ technology pumps air into a tube full of calcium oxide pellets. The tubes are heated via parabolic mirrors. At 400 degrees the CO2 reacts with the pellets to form calcium carbonate. Heated to 1000 degrees, pure CO2 is driven out of the pellets. Solar scrubbers would only operate in conjunction with solar energy and would be most effective in desert regions with CCS infrastructure.
? Adding alkalinity to seawater is another possible means of capturing CO2. This involves decomposing heated limestone into lime and CO2.The CO2 is sequestered and the lime is added to seawater, where it acts to enhance the capacity of the oceans as a carbon sink by drawing CO2 out of the atmosphere and storing it as bicarbonate ions in the ocean. The process requires large amounts of limestone, energy, CCS infrastructure and access to the ocean. Possible locations include Australia, Namibia and Oman. 80 MtCO2 per year would require approximately 120 Mt of limestone.
The two engineered air capture technologies of level 3 could also be deployed on a global scale under level 4.
In summary, this level 4 of geo-sequestration estimates a negative emissions potential of 111 MtCO2 per year in 2050 (80 MtCO2 per year from international geo-sequestration processes plus 30 MtCO2 per year from UK engineered air capture techniques and 1 MtCO2 per year from other UK sources). As the energy cost of the international engineered negative emissions have such a significant range and will not need to be covered by UK production, the 2050 Pathways Calculator does not account for them. A significant UK financial contribution to any such international negative emissions programme is to be expected.
Costing level 4:
Case study of artificial 'carbon trees' - Klaus Lackner
Klaus Lackner states that the cost per tonne of CO2 removed from the atmosphere by early prototype machined would be around US$200/tCO2
|-||This includes capital costs of individual air capture units at about US$200 000/t.CO2. Such machines would capture on average 1tCO2 per day.|
|-||And anticipated US energy prices for operation.|
Through learning effects, mass production and improvements in operation, the performance of the units could improve to 1-3tCO2 per day and the capital cost reduced to about US$20 000 per unit. The price of air capture could then drop as low as US$30-90/tCO2 (this includes an estimated transportation and storage cost of US$1-12/tCO2).
Own calculation for international roll-out:
Capital cost for 250 000 air capture machines: 5,000,000,000 US$ We estimate machines will last for 20 years, this equates to roughly 250mio US$ per year. This equates to roughly US$3/tCO2
Operational cost: Lackners approach also necessitates chemicals, water and CCS facilities. Basically, this should cover what is left of the US$30-90/tCO2 after considering fuel cost and capital cost.
Fuel cost: Estimated volume for 80tCO2 is 40 TWh to 130 TWh per year. Lackner supposedly uses ‘anticipated US energy prices’. But there is also an argument for fuel costs to be much lower. Major decisions making points on where to deploy will be space available in a dry climate, carbon capture resource and availability of energy. This energy could be generated by purpose-built fossil fuel/nuclear powerstations, concentrated solar or even utilise ‘stranded gas’ reserves, which supposedly offer up to 90% below market prices.
The 2050 Calculator uses for the 80 MTCO2 of international geosequestration a cost range of $30/tCO2 to $600tCO2. $30/tCO2 reflects the lowest price estimate a credible participant in the geosequestration field has estimated in case of a mass rol-out of a mechanical air capture technology over the coming decades. As an upper range the 2050 Calculator references a recent study from the American Physical Society on 'Direct Air Capture of CO2 with Chemicals' which puts forward $600tCO2 as a cost estimate. Cost estimates of other geosequestration technologies appear to be within this - relatively broad - price range.
As a further 'pointer' for estimating prices, the 2050 cost calculator also introduced a 'default' price which is the 35th centile between the sector's low and high ranges. For the level 4 geosequestration estimation it is £143 t/MtCO2e.
Some references on geo-sequestration activities:
http://royalsociety.org/Geoengineering-the-climate/ http://www.imeche.org/knowledge/themes/environment/climate-change/geo-engineering http://www.aps.org/policy/reports/popa-reports/loader.cfm?csModule=security/getfile&PageID=244407 http://www.carbonengineering.com/wpcontent/uploads/2011/05/CE_APS_DAC_Comments.pdf http://www.virgin.com/people-and-planet/blog/virgin-earth-challenge-announces-leading-organisations
www.climeworks.com http://www.pre.ethz.ch/ (http://www.pre.ethz.ch/publications/journals/full/j236.pdf) http://www.wipo.int/pctdb/en/wo.jspWO=2010107974&IA=US2010027761&DISPLAY=STATUS www.carbonengineering.com www.kilimanjaroenergy.com www.globalthermostat.com / http://scholar.google.com/scholar?hl=en&as_sdt=0,5&q=chichilnisky+eisenberger
http://www.blackcarbon.dk/BiocharApplications.aspx http://www.biocharsolutions.com http://www.biochar.org.uk/ http://www.dtu.dk/English/Service/Phonebook.aspx?lg=showcommon&id=274130 (PDF= http://orbit.dtu.dk/getResource?recordId=274130&objectId=1&versionId=1)