Method for Preparing a Powder from Brown Macroalgae and Method for Fabricating Rigid Objects from Said Powder

A method for preparing a powder from brown macroalgae, intended for the fabrication of rigid objects, characterized in that the method comprises the following steps, in this order:

• harvesting and washing the brown macroalgae;
• treating the brown macroalgae with weak acids, by immersion of said macroalgae in a weak acid bath and/or spraying the weak acid onto said macroalgae;
• grinding the brown macroalgae;
• filtration, so as to extract a residue of non-solubilized algae;
• grinding the residue and then drying the residue for 5 to 48 hours at a temperature of 30° C. and 60° C., so as to obtain a powder with a particle size of between 0.5 and 1.5 millimeters and presenting a residual moisture content equal to or less than 26% by mass.