Characterization of mussel shells as a bio-based building insulation material
In Galicia, 35% of mussel culture is intended for canning. This industry has 25 thousand tons per year of waste (i.e., shells) that mainly ends in landfills or at the bottom of the sea, thereby producing an important environmental impact. After performing a heat treatment, mussel shells become a by-product which is suitable for different uses (poultry feed or bed, soil acidity correction, and fertilizer). However, a minority output and other avenues target related to this by-product must still be explored.
Building insulation materials commonly cause significant harmful effect on the environment, especially if their entire life cycle is analysed (the use of large amounts of energy and water for their production, the difficulty to be recycled, or the reuse of waste in the case of demolition or reform, etc.)
The use of mussels could close the circle of the economy related to the canning industry in Galicia.
The aim of this research is to prove the feasibility of mussel shells as a part of building solutions. Suitable thermal and acoustical characteristics of shells as a building insulation material have been found. The confined mussel shell inside a closed space (e.g., in a wooden box) has a thermal transmittance similar to an expanded clay or a light conifer wood, so it can be considered as a material of low thermal conductivity. Moreover, several acoustic studies indicate that a section of confined mussel shell presents a behaviour similar to a double-glazed window. Different building solutions have been designed using shells as a filling insulation material. First, they were tested in a laboratory and then in an experimental building of 60 square meters (Biovalvo Modulus). These modulus mussel shells were used in the roof, the walls and the foundation. Nearly 50 tons of treated mussel shells were converted into a useful by-product which was used as a bio-based building material.