Cement manufacture is a significant source of Global CO2 emissions. About 3.4% to 5% of anthropogenic CO2 is emitted from the Cement manufacturing process. The process of manufacturing portland cement requires the burning of large amounts of fossil fuels. In addition the cement manufacturing process triggers the emission of even larger amounts of CO2 as a byproduct of heating raw materials. Lisa J. Hanle, Kamala R. Jayaraman and Joshua S. Smith point out, Cement is often considered a key industry for a number of reasons. To begin with, cement is an essential input into the production of concrete, a primary building material for the construction industry. Due to the importance of cement for various construction-related activities such as highways, residential and commercial buildings, tunnels and dams, production trends tend to reflect general economic activity.
In addition to the emission of CO2 by burning fossil fuels during the production of cement and the the discharge of CO2 from raw materials during cement processing, the burning of fossil fuels to produce electricity used while grinding cement clinkers also contributes to the atmospheric CO2 burden. Burning fossil fuels in cement manufacturing also releases a significant amount of NOX and SO2 gases, creating further environmental problems. There has as of yet been no environmentally satisfactory solution to the cement manufacturing issues, involving the substitution of renewable energy for fossil fuels.
The relation between cement and CO2 is actually complex. Cement in concrete actually goes through prolonged chemical curing processes, during which over half of the CO2 emitted during the manufacturing process is reabsorbed. Thus the CO2 produced by burning fossil fuels during cement manufacture constitutes a separate issue from the CO2 emitted by raw materials, because much of the latter CO2 will later be recaptured later on.
CO2 emissions from materials can be controlled by using a low carbon emissions cement manufacturing process, that might begin with different materials, or inclusion of alternative materials in the raw materials mix. Alternatively carbon recapture could be facilitated during the curing process.
Carbon emissions from burning fossil fuels while processing cement materials, can be eliminated use of nuclear power in the heat production process. One approach would be the production a carbon neutral flsmable gas using process heat from a reactor. The gas would then be burned to provide sufficient heat to process cement raw materials. There are decarbonization objections to this approach, Even if the gas manufacturing process is carbon neutral, we may not be assured of carbon neutrality during all stages of handling and use. For example methane has a far more serious greenhouse implications than CO2 does. Methane lossed inadvertantly to leaks is not carbon neutral, as is methane loses due to imperfect combustion. Thus the introduction of carbon based gases into the cement manufacturing process, presents significant challenges if carbon neutrality is the goal.
There would be no such problem if the gas were hydrogen. My well informed readers will recognize that there are problems with the handling and storage of hydrogen, but those probles relate more to the storage of hydrogen than its production. The hydrogen problems can be minimalized if hydrogen is burned immediately after its production.
Nuclear power can contribute to cement manufacture, both by serving as the indirect source of the required heat input, and as a carbon free source of electricity.
Both gas cooled and liquid salt cooled reactors could be useful in cement manufacturer, but LFTRs have the potential to perform the heat production role with the lowest potential cost. The LIFT would be the energy source that is most compatible with high energy post-carbon future. It has the greatest potential to produce industrial heat and electricity at a low cost, while for all practical purposes, energy produced by LFTRs would not be limited by natural forces or supply problems.
If decarbonization is imagined to be adressed on a sector by sector basis. In terms of electrical generation decarbonization can take place by substituting nuclear power for fossel fuel generating systems. In surface transportation, decarbonization can be accomplished by electrification. Space heating can also be electrified, especially through use of heat pumps. Finally energy for the industrial sector can be provided by greater electrification or by nuclear heat inputs.
This vision would assign to nuclear power a predominate role in the production of post carbon energy. It is quite evident that this role could not be fulfilled by conventional light water nuclear technology. First because of the limited avaliability of U-235. By a switich to Generation IV nuclear technology, energy avaliability of current supplies of nuclear fuel would be increased by a factor of 500 or more.
The program endorced by Nuclear Green is highly ambitious. I advocate the use of nuclear powered energy sources in the creation of a globalized high energy industrialized economy. My view is that this program is not incompatible with environmental values, infact it is more consistent with environmental protection than a low energy renewables powered post-carbon future. In addition, a post carbon high energy future would be less likely to produce the political and economic conditions that would lead to war.
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