Cambridge Electric Cement ($4 million to recover used cements by using the steel recycling process)

Cambridge Electric Cement, a UK cleantech company founded in 2022, is dedicated to developing a cement with zero emissions. They achieve this by utilizing used concrete waste as flux in steel recycling electric arc furnaces. The resulting steel slag closely resembles the composition of cement. This innovative process not only tackles the substantial carbon emissions linked to conventional cement manufacturing, but also seamlessly incorporates steel recycling to create a self-sustaining cycle.

Challenges: cement emissions

Cement production is a significant contributor to carbon dioxide (CO₂) emissions, making up approximately 8% of the world's total CO₂ emissions. The production of cement involves a chemical reaction known as calcination. During this process, limestone (CaCO₃) is heated to temperatures exceeding 1400 ºC in a kiln, resulting in the production of lime (CaO). This process results in the release of carbon dioxide (CO₂) as per the given reaction:

CaCO₃ + heat → CaO + CO₂

In addition, cement production necessitates significant energy consumption for heating the kiln and grinding raw materials into the fine powder utilized in cement manufacturing. Energy used in cement production primarily comes from the combustion of fossil fuels like coal, oil, and natural gas, resulting in the emission of CO₂ into the atmosphere.

There are several main strategies to reduce emissions from Portland cement production.

  • Utilizing alternative fuels like hydrogen (H₂), fossil gas, municipal waste, or biofuels as substitutes for fossil fuels.
  • Using low-carbon raw materials, such as industrial byproducts of fly ash and slag and recycled materials.
  • Using Carbon Capture and Storage (CCS) to reduce carbon emissions from cement plants.

Nevertheless, these approaches are insufficient to achieve complete elimination of emissions.

Currently, electrification and the burning of hydrogen or biofuels are the most viable options to meet the necessary heat and temperature demands. Nevertheless, all of them come with notable disadvantages: expensive price, limited scalability, challenging procurement process, and extremely low efficiency.

Ground-granulated blast furnace slag and fly ash, the two most commonly used substitution materials, are derived from primary steel production and coal power stations. These sources are known for their high emissions and need to be eliminated as we move towards achieving zero emissions.

CCS has been considered as a potential solution for reducing emissions in challenging sectors like cement. However, its implementation has been cautious, and it is highly unlikely that it will be widely adopted and operating at a significant scale by 2050. As a result, it is doubtful that construction activities will be able to maintain the same emission levels as today. In addition, numerous ongoing projects focus solely on capturing process emissions, without any emphasis on storage.

According to projections, a significant surge in cement demand is expected due to the construction of approximately 75% of the infrastructure that will be in place by 2050. Typically, concrete structures are disposed of in landfills once they have reached the end of their useful life and have been demolished. Thus, the production of low-carbon cement and the recycling of used cement are crucial pathways to attain zero-carbon cement.

Cambridge Electric Cement Technology

Cambridge Electric Cement has successfully developed an economical, industrial-scale cement production process that is completely carbon-neutral. This achievement was made possible by integrating steel recycling and clinkering techniques. The company utilizes recycled concrete waste as an alternative to the lime-flux typically employed in electric arc furnaces (EAFs) for steel recycling. When the steel melts, the concrete waste forms a slag. The rapidly cooled slag closely resembles the commercial Portland cement.

How Cambridge Electric Cement produces low-carbon cement

The diagram below illustrates the process of converting used cement paste into high-quality new cement using electric arc furnaces (EAFs) in steel recycling, taking advantage of the high temperature.

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