While environmental advocates urge governments to increase limitations on greenhouse gas emissions, scientists all over the world are searching for carbon sequestration techniques to offset what does get emitted. Looking to nature for inspiration has led to innovation in many scientific arenas, and opportunities to let mother nature lead the way towards carbon capture seem to be emerging with recent discoveries. Conversion of dissolved carbon dioxide (CO2) in ocean water to the calcium carbonate (CaCO3) species that form the shells and exoskeletons of some marine organisms has been ongoing for many millions of years. As anyone who frequents scientific columns probably knows, some scientists in the UK recently discovered a mechanism utilized by sea urchins for carrying out this reaction. The high likelihood of translating the method into one humans could use for capturing anthropogenically produced CO2 in non-oceanic systems has got some folks calling the discovery a potential “game changer”.
CO2 mineralization as a method for carbon capture is referred to as “geologic sequestration”. While it has been considered in the past, the costs involved in translating this method from marine animal utilization to industrial-scale process has excluded it from any list of feasible high volume carbon-capture options. The limiting factor is in the necessity for a catalyst to perform the reaction. Previous candidate catalysts have included peptoids[i], and the most promising former option, the Carbonic Anhydrase enzyme. The need for specific reaction conditions (including pH, temperature, and pressure), the costs involved in extracting or reproducing biological enzymes, and the poor regenerative capacities of known catalysts have been some of the most notable hurdles.
Scientists in the UK recently discovered that sea urchins turn CO2 into CaCO3 for construction of their exoskeletons via nickel catalyst[ii]. Unlike other known catalysts that perform similar reactions, nickel operation is pH independent, doesn’t require the addition of energy, requires no additional reagents, and has a recovery rate greater than 99%, which means it can be reused many times. The study found that CO2 pumped through water containing suspended nickel nanoparticles was 100% retained in the water. The next step of the mineralization process does not require catalysis, making for simple conversion of the intermediate product to CaCO3. Dr. Siller, head of the group that made the discovery, has suggested application of this technology in industrial systems like power stations and chemical processing plants that produce large quantities of CO2[iii]. Small reservoirs of water containing nickel nanoparticles at concentrations of 30 ppm could intercept the CO2-rich output streams at these industrial sites, trapping the gas in the water column.
The discovery of a cheap and widely available catalyst is promising especially due to the fact that the end product, CaCO3, is chemically inert. In terms of cost, nickel could provide an alternative to the Carbonic Anyhdrase enzyme at a thousandth of the price. The estimated cost incurred per ton of CO2 captured is cited at ~$7.9, considering the recycling potential and low cost of nickel. Additionally, the opportunity to sell the CaCO3 output represents potential for entirely offsetting the costs of the sequestration system. CaCO3, a chalky substance, is used in industries such as paper/pulp, plastics, cement, and paint. These industries are estimated to consume over 85 million tons of CaCO3 per year, resulting in markets that bring in roughly $650 billion/yr. Other proposed methods for capturing industrially-produced CO2 include the underground storage of CO2 in expired oil pockets or in deep ocean sites. The cost of transportation of CO2 to these sites, alongside the measures likely to be taken to ensure that leakage won’t occur, represent downsides to these methods that won’t be present were CO2 to be converted to CaCO3.
Because this technology is low-cost and could be utilized without much re-structuring of the industrial settings in which it would be useful, the political and economic feasibilities of its widespread deployment seem reasonable. The buzz all over scientific columns in the last couple of weeks has been calling this finding ‘a potential solution to the challenges of carbon sequestration’. Will it be? Only time will tell. It is, however, important to remember that these technologies are still bandaids for our dirty energy economy, and thus shouldn’t be adopted in lieu of clean energy advancements. But considering how far off we are from 100% clean energy, news regarding promising new sequestration techniques is good news.
[i] Chen, C., Zuckermann, R. “Carbon Sequestration via CO2 Mineralization”, Lawrence Berkeley National Lab. May 6, 2011. http://ei.haas.berkeley.edu/c2m/pdf/2011EndofYearSlides/Carbon%20Sequestration.pdf
[ii] Bhaduri, G.A, Siller, L. “Nickel Nanoparticles Catalyze Reversible Hydration of Carbon Dioxide for Mineralization Carbon Capture and Storage”, Catalysis Science & Technology, The Royal Society of Chemistry, Jan. 2013.
[iii] Science News, “Could the Humble Sea Urchin Hold the Key to Carbon Capture?”, Earth & Climate. Feb, 2013. http://esciencenews.com/articles/2013/02/05/could.humble.sea.urchin.hold.key.carbon.capture
Read more: http://2ndgreenrevolution.com/2013/02/20/mother-nature-the-master-innovator-as-usual/#ixzz2LY8Rq4kg
