Page 55 - 2022 Sustainability Report
P. 55

ENVIRONMENTAL STEWARDSHIP



        Cement Manufacturing

        Carbon dioxide (CO ) emissions are an unavoidable component of manufacturing cement due to the nature of the raw
                         2
        materials and chemical reactions involved. In particular, the calcination process that is chemically necessary to transform the
        raw materials used in manufacturing cement has the side effect of driving out the CO naturally found in the limestone
                                                                                2
        which is the main ingredient of cement. It is this CO that makes up the bulk of emissions from any cement plant.
                                                    2
                                                                                  1  Limestone and other raw
                                                                                     materials quarried

                                                                                  2  Raw materials are ground
                                                                                     and blended

                                                                                  3  Raw materials are heated
                                                                                     to 2,850° F in a kiln

                                                                                  4  Heat transforms the materials
                                                                                     into pellets of “clinker”
                                                                                  5 Clinker is ground with gypsum
                            1                      5                       6
                                                                                     cement

                                                                                  6 Cement is stored and shipped
                                                                                     via truck or rail

                                                                                  7  Primary end use consumption
                                                                                     is concrete



        During the calcination process, limestone is heated in excess of 2,800 degrees Fahrenheit. This breaks down the molecular
        structure of the stone into clinker (mainly comprised of calcium oxide (CaO) compounds) and CO gas. While the solid
                                                                                           2
        clinker is subsequently ground and incorporated into cement, the CO is emitted from the plant. In a modern kiln, more
                                                                   2
        than 50 percent of the Scope 1 GHG emissions are a result of this calcination process, with the remaining emissions
        coming from the combustion of fuels needed to heat the kiln and the on-site generation of electricity. 1
        Cement producers have limited ability to abate or reduce process emissions resulting from calcination due to the fundamental
        chemical composition of the limestone. While awaiting development of commercial-scale carbon capture and storage
        technologies that may provide new, practical means of addressing the CO emitted from limestone, cement producers must
                                                                     2
        focus on opportunities to use lower-carbon fuel sources and improving energy efficiency in the manufacturing process.

        Carbon Capture and Sequestration


        As recognized by a number of international organizations (including the International Energy Agency) as well as various
        industry associations, the cement sector’s ability to limit GHG emissions levels in a manner consistent with the goals of the
        Paris Agreement depends on successful future development and implementation of carbon capture and sequestration (CCS)
        and other innovative technologies on a commercial scale. In fact, the IEA in its September 2022 report on the cement sector
        states that in order to achive net zero and alignment with the Paris Agreement: “(s)harper focus is needed in two key areas:
        reducing the clinker-to-cement ratio (including through greater uptake of blended cements) and deploying innovative
        technologies, such as carbon capture and storage and clinkers made from alternative raw materials.” However, the IEA notes
        in discussing CCS and other technological changes that “(a)ligning with that scenario (the net zero scenario) will require the
        development and deployment of technology that is not currently available.” Similarly, further acceptance of even lower
        clinker content cements by Departments of Transportation and ASTM in the United States will also be critical in allowing the
        cement sector to achieve carbon neutrality across the value chain by 2050. We are monitoring these developments closely.
        1  Testimony for the Congress of the United States House of Representatives Select Committee on the Climate Crisis hearing on “Solving the Climate
          Crisis: Reducing Industrial Emissions Through U.S. Innovation”, September 26, 2019. Jeremy Gregory, PhD, MIT on behalf of the PCA.


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