A promising alternative to CCS is using algae to ‘eat’ CO2 emissions and produce fuel at the same time. Because of their substantial emissions, cement plants would be ideally suited for deployment of this innovative technology. Several projects, including large-scale undertakings in Spain and France, are currently underway to test the technology.
CO2 from the chimney stack is fed into open reservoirs containing algae or into a dedicated closed system. Like all green terrestrial plants, microalgae grow by photosynthesis and their development requires light (natural or artificial), CO2, water and some nutrients (mineral salts). The more CO2 is fed to the algae, the better they grow.
The algae can then be harvested and dried (possibly using waste heat from the cement plant), before being used as a fuel for the cement kilns. Alternatively, algae biomass can be processed into third-generation biofuels, bio-plastics or high-value-added compounds like antioxidants, lipids or proteins.
The technology is still at a very early stage of development. Research projects will help to determine the functional and economic feasibility of industrial organic biomass production and how to incorporate this technology into the manufacture of cement. Applications of biological capture of CO2 emissions at the scale of cement plants must address the sustainability of significant demands on land use and resource use.
It is too early to make any accurate predictions on potential CO2 savings.
Algae technology offers a solution for CO2 capture, as well as biomass fuel production that could potentially be suitable for smaller plants where CCS deployment is not an option. The research is, however, still at quite an early stage. Further research would need to be encouraged to discover its full potential.