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AAC WORLDWIDE %u2022 2.2025 SCIENCE & INNOVATION 33products such as blast furnace slag or fly ash from incinerators to partially replace Portland cement. With respect to the aerating agent, however, there have been no significant innovations from an environmental point of view, as aluminium powder has remained the only component used to activate the aeration of cement. Different methods of aeration concern in particular non-autoclaved cellular concretes, in which the formation of air voids is achieved through the introduction of a volumetric fraction of preformed foam within the cement paste.Further experiments [3] were carried out using H%u2082O%u2082 as an aerating agent for a concrete obtained from a geopolymer fly ash matrix, demonstrating the formation of microporosities similar to the material aerated with aluminium powder with the same density and mechanical performance.Totally innovative, however, was the methodological approach that led ENEA to the development of a new aerating agent, which is the result of combining the expertise gained in technological research of innovative materials for energy efficiency with that of biological processes. The new aerated concrete is based on the simplification of conventional constituent materials and the use of microorganisms as a source of enzymes capable of breaking down hydrogen peroxide into oxygen and water. The results of the experimentation led to a final product that is very similar to the commercial product in terms of density, mechanical strength, thermal and acoustic conductivity and that holds great potential for environmental sustainability.Experimental approach As is well known, aluminium powder reacting with calcium hydroxide in an alkaline environment (pH %u2265 12) and in the presence of free water, produces, due to the oxidation of the metal, molecular hydrogen according to the following reaction:2Al + 3Ca(OH)%u2082 + 6H%u2082O = 3CaO%u2219Al%u2082O%u2083%u22196H%u2082O + 3H%u2082%u2191(g)The development of H%u2082 results in a porous structure within the mix matrix, which once hardened will have a volume 1.5 to 5 times that of the original cement slurry. The rising process stops when the material reaches a solid consistency: the voids stabilise in the material matrix and the hydrogen content is gradually released into the atmosphere and replaced by air.Bio-aeration, which produces Bio-Aerated Autoclaved Concrete (BAAC), is the result of the dismutaPiero De Fazio is a research executive at ENEA, the National Agency for New Technologies, Energy and Sustainable Economic Development, an Italian public research organization. He is Head of the Section %u201cProcesses and Materials for Energy Applications%u201d and works in the Department of Energy Technologies and Renewable Energy Sources. He has been Scientific Head and coordinator of several research projects funded by public administrations, focused on the development of innovative materials for energy efficiency. Co-holder of two patents in the field of materials, he has authored numerous publications focusing on characterization techniques and the study of durability of building materials.%u00a0 piero.defazio@enea.itGiorgio Leter has been a senior researcher in the field of human and animal biology at ENEA, the National Agency for New Technologies, Energy and Sustainable Economic Development. He has collaborated on numerous national and international research projects, mainly on the toxicology of the male reproductive system and in general on the effects of nano-scaled oxides on animal systems in vivo and in vitro. He collaborated in the conception and development of a patent for bio-aeration of cementitious building materials. He is the author of numerous publications in national and international scientific journals. gleter110@gmail.com