7.3 Is Mineral Carbonation for CO2 storage a clean technology?

Jim Petrie , Chemical Engineering, University of Sydney, Sydney, Australia

As the world grapples with the real consequences of inaction against climate change, carbon capture and storage technologies are perceived as attractive (and necessary)[1] mitigation options for CO2 release from fossil energy plants in the transition to a renewable energy future. However, the focus to date has been almost entirely on geo-sequestration, and there are concerns about such a technology being deployed in time, and at sufficient scale, to make a major impact on desired CO2 reduction targets. As an alternative, mineral carbonation, the reaction of carbon dioxide with magnesium silicate minerals such as serpentines, represents a thermodynamically favourable, safe, and readily auditable route to the sequestration of carbon dioxide. But this technology is itself both energy intensive and resource intensive, and so the question to be answered here is the following:

“Are there conditions under which mineral carbonation for CO2 storage from fossil energy generation plants can be considered a clean technology?”

Definitions of “clean technology” are generally relative. As a starting point, it is a technology which delivers gains in economic efficiency and reductions in environmental impact over competitive processes; in other words an “eco-efficient” option. Beyond this, the paradigm of “clean technology” has evolved and broadened to now sit within a sound philosophical framework of sustainability and sustainable development, to include consideration of social benefits from the deployment of such technology. The potential social impacts of climate change are catastrophic, which demands immediate, sustained, and global attention be given to the problem of atmospheric CO2 reduction.

Given that there are no full scale commercial processes for CO2 sequestration[2], such an evaluation is difficult.  Comparative assessments are made even more difficult due to inconsistencies in spatial and temporal system boundary definitions, selective inclusion of environmental issues, and befuddlement caused by value judgments. When the impetus of action to combat climate change is added to this mix, the call is even more difficult. Whilst there have been some attempts to conduct a life cycle assessment of mineral carbonation[3], these have been based on laboratory scale information only, and are of marginal value in answering the question posed above.

As a contribution to this discussion, this paper examines a prototype full scale mineral carbonation plant, based on the Albany Research Center process[4] , which has been identified by the IPCC [5] as being most fully developed and with the greatest immediate potential for commercialization, despite anomalies identified by other researchers in the field[6].   This prototype has been developed using the ASPEN Plus modeling environment, and due consideration has been given to energy minimization, water conservation, by-product utilization, and waste management. CO2 sequestration efficiencies in the order of 80% are achievable, under a realistic set of process development assumptions. Capital and operating costs for such a plant have been reviewed. Using a simple discounted cash flow analysis, it is possible to suggest at what price carbon dioxide emissions would need to be traded  in order for such a process to be deemed “economic”, in the narrowest sense.

Returning to the question, it is postulated that mineral carbonation could indeed be deemed a clean technology under the following conditions:

  • At the macro-scale: the technology is fully developed and deployed in short order, and at large scale, on CO2 streams which are capture ready; to effect short term reductions in atmospheric CO2, whilst renewable energy options are further developed
  • At the meso-scale: mineral carbonation should be pursued as an anchor technology within an integrated minerals-energy complex, stimulating its own industrial ecology, wherein synergistic opportunities for material and energy exchange are exploited to the mutual benefit of all partners in such a collaborative network. The added value created by such a complex has the potential to significantly off-set the direct costs and energy penalties of mineral carbonation.
  • At the micro-scale: process optimization for energy integration is pursued aggressively.

Ultimately, however, the potential success of this technology hinges on sustained societal pressure to combat climate change, global political will, and efficient economic instruments to stimulate carbon markets.

[1] Metz, B., Davidson, O., De Coninck,  H., Loos. M and Meyer, L. (eds) (2005) Carbon Dioxide Capture and Storage - IPCC Special Report, UN Intergovernmental Panel on Climate Change, ISBN92-9169-119-4.

[2] The Sleipner gas field project in the North Sea, which remains the world' biggest pilot, sequesters only 1 MTe/annum CO2. A single 1000 MWe coal fired power station generates 13-15 MTe/annum of CO2.

[3] Hsien H. Khoo and Reginald B.H. Tan (2006), Life Cycle Evaluation of CO2 Recovery and Mineral Sequestration Alternatives”, Env. Prog &Sust. Energy 25(3), 208-217

[4] O'Connor, W.K., Dahlin, D.C., Rush, G.E., Gerdemann, S.J., Penner, L.R. and Nilsen, D.N. (2005) Aqueous Mineral Carbonation - Mineral Availability, Pre-treatment, Reaction Parametrics, and Process Studies-Final Report, DOE/ARC-TR-04-002,Albany Research Center, US DOE.

[5] Metz, B., Davidson, O., De Coninck,  H., Loos. M and Meyer, L. (eds) (2005) Carbon Dioxide Capture and Storage - IPCC Special Report, UN Intergovernmental Panel on Climate Change, ISBN92-9169-119-4.

[6] Sipalä, J., Teir, S. and Zevenhoven, R. (2008) Carbon dioxide sequestration by mineral carbonation - literature review update 2005–2007. ISBN 978-952-12- 2036-4, Åbo Akademis Tryckeri, Finland.