Alternatives to CCUS
Alternative fuels. The cement industry can meaningfully reduce emissions from the combustion process by replacing traditional fuels like pet coke, coal and natural gas with alternative fuels like biomass and various types of waste. Alternative fuels currently account for nearly 30% of the cement industry’s fuel consumption in the EU and 15% to 20% in the U.S. (although as many as 70% of kilns are estimated to use some level of alternative fuel). Austria — to name one country — has reached a substitution rate of around 80%, making it clear that the industry has significant room to increase alternative fuel adoption globally.
Despite the progress that cement makers and public authorities are making, however, adoption has been relatively slow and is likely capped by access to feedstock.
In Europe, biomass and other types of waste that can be used as alternative fuels are typically routed to incinerators. Like cement kilns, these require continuous supply to operate and, increasingly, methanization plants. In other parts of the world, the availability of biomass and waste from agricultural and forestry sources is limited (e.g., much of the Middle East). Finally, plastics recycling further cuts into potential feedstock availability.
Overall, the European trade group Cembureau estimates that alternative fuel penetration could reach 60% by 2050. For cement’s total CO2 emissions in Europe, that represents a reduction of around 12% over a long period of time, which is significant but fails to address the fundamental chemical emissions from the decomposition of calcium carbonate.
Cementitious materials. Another effective way to reduce emissions from concrete is to substitute cement with CO2-free hydraulic binders. But blast furnace slag, the most efficient type of cementitious material, is already widely used and sought after. And in developed countries, the availability of fly ash — a byproduct of coal power plants and the most widely used type of cementitious product — is running into feedstock constraints due to coal power phaseouts (see Figure 1).