Building materials for the construction industry provide an interesting example of mineralisation. In natural carbonation reactions, carbon dioxide reacts with calcium or magnesium minerals, to produce carbonates, the main constituent of limestone. By modifying the reaction conditions using accelerated carbon technology, these reactions can be performed much faster than the natural process. Many industrial residues generated by thermal processes, such as cement kiln dust, iron and steel slag, coals fly ash and bauxite residue, containing lime or appropriate calcium silicates can readily react with carbon dioxide. In doing so, the contaminants in the residues are stabilised and solidified so that they can be used to manufacture new products.
Carbon dioxide has been used to manufacture polymers, such as polyurethanes and polycarbonates. The polymers may comprise 30 to 50% by mass carbon dioxide in the polymer backbone. Polymer products made from carbon dioxide are being commercialised by various companies. These and other polymers that use carbon dioxide offer a range of performance and functionality suitable for commercial application in multiple industry sectors, especially where sustainability is an important product attribute. Polymers derived from carbon dioxide can be produced and processed using the existing infrastructure for petrochemical based polymer manufacturing.
Apart from the utilisation of the captured CO2 as a material resource, it is also possible to use it as a base resource in combination with hydrogen for the synthesis of chemical energy carriers. This pathway opens the possibility of producing a broad range of fuels for use in stationary as well as mobile applications. In this context, methane is a very common energy carrier worldwide. It is the main component of most resources of “natural gas”. The most common use of methane or natural gas, for instance, in Germany, is for the supply of heat in house-holds. Also, natural gas power plants have gained an increasing share of Germany’s power production mix due to their good dynamic characteristics compared to the predominant existing coal power plants. Furthermore, natural gas can be used in cars as a substitute for gasoline in Otto engines. Because of its higher H:C ratio, this technology has the potential to reduce direct CO2 emissions in passenger cars in comparison to conventional gasoline or diesel fuel. The production of methane on the basis of sustainably-produced H2 via electrolysis would therefore quickly find use in the existing infrastructure and markets.
Similarly to methane, the use of methanol is widespread and versatile around the world. Part of the reason for this is that methanol can not only be used as an energy carrier, but also as the feed material for many chemical processes. This gives sustainably-produced methanol manifold opportunities for market implementation. The conventional method of producing methanol is a chemical synthesis based on synthesis gas (H2 + CO), which is mainly produced by means of steam reforming of natural gas, but can also be made via the gasification of coal or biomass. In the past years, numerous research projects have dealt with methanol synthesis from H2 and CO2 feedstock. The largest fully operating commercial power-to-fuel plant is the George Olah plant from CRI (Carbon Recycling International) in Iceland, which produces 5 million liters per year of climate-friendly methanol using geothermal power. Moreover, the production of methanol offers a new route to a range of commodity and platform chemicals including acetic acid, olefins, vinyl acetate, ethyl acetate, ethanol, ethylene glycol and higher alcohols.
Some interesting links:
CO2 conversion into polymers by Econic Technologies. See http://econic-technologies.com/how-it-works/
George Olah carbon dioxide (CO2) to renewable methanol plant. See https://www.chemicals-technology.com/projects/george-olah-renewable-methanol-plant-iceland/
Some scientific references:
Zhu Y, Romain C, Williams C. 2016 Sustainable polymers from renewable resources. Nature. 540, 354-362 (doi:10.1038/nature21001)
E. Billiga, M. Decker, W. Benzinger, F. Ketelsen, P. Pfeifer, R. Peters, D. Stolten, D. Thrän (2019). Non-fossil CO2 recycling—The technical potential for the present and future utilization for fuels in Germany. Journal of CO2 Utilization 30, 130-141 (doi: 10.1016/j.jcou.2019.01.012)
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