Bioterra : control of the microbial proliferation on earth bio-based products for healthy and sustainable buildings – BIOTERRA

The BIOTERRA project will focus on four technical tasks which will add a task on the project management and another on the valorization of the results. The first task will aim to choose the raw materials (erath and plant materials), to manufacture the products under study (bricks and plasters) and to identify microbial strains present in cultural heritage earthen habitat and in raw materials used for the study. Tasks 2 and 3 will be carried out in parallel and will be strongly interdependent. Task 2 will focus on properties use of the studied materials, particularly their hygrothermal properties that affect comfort but also microbial proliferation studied in Task 3 (sub-themes 2.2 and 2.4). The use of modeling will deepen the experimental results (subtopic 2.3). The main goal of task 3 is the study of parameters affecting the growth of microbial strains identified and isolated in task 1 and some solutions to limit the proliferation of these microbial strains will also be studied (various recommendations and microbiological control). Identification of microbial strains
(Task 1) and the study of their proliferation (Task 3) will be based on the development of new methodologies (subtopic 2.2). Finally, the task 4 will enable the tasks 2 and 3 with large scale including the monitoring of a building with removable inside walls made ??with earth materials studied in this work (subtopic 2.4).

The part of the task 1 concerning the choice of the raw materials and the manufacturing of the products is finished. Two types of earth (fines from aggregate washing sludge (FWAS) and a kaolinite used in CEREMA for clay plasters) and five aggregate plants (flax fibers, straw, hemp, corn cobs and residues of cork) were selected. The part concerning the sampling and on-site identification of microbial strains present in buildings from the heritage will start during the autumn 2015.

Concerning Task 2, the basic characterizations on all the selected materials are complete and allow to show the important contribution of plant aggregates. The laboratories concerned by this part of the study have begun to characterize the materials more deeply especially in terms of hygrothermal performances and the use of modeling will allow to deepen the analysis of experimental results.

The main objective of task 3 was the study of microbial strains proliferation identified and isolated in task 1. LGC (P4) started a part of this task by the study of microorganisms present on the raw materials (FWAS, straw and hemp used LMDC (P1) and samples of clay plasters sent by the CEREMA (P2)). Proliferation tests will start in the month of January 2016 with a student of Master.

Finally, the task 4 on industrial validation of results should start at the beginning of the last year of the project (January 2017) as originally planned.

Compositions of biobased earth bricks that are extrudable and with high performances: adding hemp or straw improves markedly the hygrothermal performance of earth bricks while maintaining high mechanical performance. In addition, we showed that formulas containing up to 6% by mass of hemp or straw were extrudable, which is promising for industrial exploitation of the results of this project.
Compositions of biobased clay plasters with high performances: tests performed in CEREMA and LGCB allowed to select three compositions of clay plasters that could find industrial outlets for interior coatings.
Methodological contributions on the extraction of bacterial and fungal on biobased raw materials: the developed methodology is now validated and controlled and will allow in particular to take and to analyse samples on buildings from the heritage.

The scientific production achieved during the first 18 months of the BIOTERRA project is relatively large and mainly concerns the participation in conferences to present the BIOTERRA project and its main objectives. Scientific production concerns both multipartner or monopartner works.

Multipartner works: 2 international communications in the conference ICBBM, an article in a French peer-reviewed journal (Materiaux et techniques) and 4 communications or popularizing conferences in France.

Monopartner works: 1 article submitted in an international peer-reviewed journal (Construction and Building Materials), one international communication in the conference ICBBM and 4 communications or popularizing conferences in France.

Nowadays, the impacts of construction on environment and health became major stakes. Problems linked with the indoor air quality are considered to be an important risk factor for human health. The current trend tends to improve environmental quality of buildings, dealing with thermal performances, hygrothermal comfort and the use of materials with low impacts.

For various reasons (patrimonial, environmental, economic…), there is a resurgence of interest in materials used by human since centuries, as earth and bio-based materials (wood, plant fibres and aggregates). Earth is said to improve moisture regulation into the buildings and consequently users’ comfort. Earth is commonly reinforced or lightened with plant matters. However, under some conditions, development of moulds was observed on the surface of these materials raising many questions as for their use.

The BIOTERRA project aims to identify, characterize and offer one (or more) solution(s), with low environmental impact, to the microbial proliferation on earth bio-based products (bricks and plasters) used for construction and restoration of health and durable buildings. This project also aims to develop and validate innovative methodologies for the identification of the microbial strains and the study of their proliferation on building materials.
BIOTERRA project is articulated around 4 technical tasks and 2 additional tasks on project management and valorization of the results. The first task will concern mostly the choice of raw materials (earth and plant aggregates), the fabrication of materials of study (bricks and plasters) and the identification of microbial strains present in earth building heritage and in the raw materials used for the study. The second and third tasks will be carried out in parallel and will be strongly interdependent. Task 2 will concern the functional properties of studied materials; in particular, their hygrothermal properties which impact comfort and microbial proliferation studied in task 3. The use of modeling will allow dealing in depth with the experimental results. The main objective of the third task is the study of microbial proliferation and their influent parameters for identified and isolated strains during task 1. Furthermore some solutions to limit proliferation will be evaluated (various recommendations and biological control in order to limit the impact on health). The identification of microbial strains (task 1) and the study of their proliferation (task 3) will be based on the development of innovative methodologies. Lastly, task 4 will concern the validation of tasks 2 and 3 on a large scale with, in particular, the monitoring of offices in building equipped with removable partition-walls made with materials of the study.

This highly multi-disciplinary project brings together 9 partners including 5 laboratories: the “Laboratoire Matériaux et Durabilité des Constructions” (LMDC), the project coordinator, the “Laboratoire Génie Civil et Bâtiment” (LGCB), the “CETE of Lyon”, the “Laboratoire de Génie Chimique” (LGC) and the “Laboratoire de Recherche en Sciences Végétales” (LRSV). The “Centre Technique de Matériaux Naturels de Construction“ (CTMNC) reinforces this consortium. Finally, three other industrial partners will participate in this project: Agencement-structure, Agronutrition et les Carrières du Boulonnais.