Development of microorganism sampling methods on bio-based earth products intended for healthy, sustainable buildings

Abstract

The impact of buildings on the environment and on the health of the inhabitants are priority issues nowadays. For many reasons, the demand for building products made of materials such as earth and bio-based materials is increasing. Under certain conditions, mold growth can be observed on the surface of such materials, which raises many questions about their use in buildings. In the framework of the “BIOTERRA” ANR project, the aim of the study was to characterize an earth based material incorporating natural fibers from a biotic point of view. Microorganism sampling methods intended for raw materials and cylindrical specimens were optimized, and the microflora profile of these materials was then obtained. The role of the dry step concerning the presence of molds was also studied. The results showed that raw materials and manufactured specimens contained mainly Bacillus sp., Aspergillus sp. and Penicillium sp. Comparisons among samples taken on the surface or the inside of the dried specimens revealed the survival of some molds despite thermal treatment. Those molds were then able to grow on specimens in high humidity conditions. Sampling methods developed here could also be used to identify the microflora of existing earthen buildings.