The present invention relates to use of biochar for preparation of construction material. In a first embodiment, a method for preparing a construction material, such as a concrete, is disclosed, wherein said method comprising the steps of combining a binder (i.e. cement), aggregate (i.e. sand) and biochar; adding an aqueous solvent to form a mixture; and allowing the mixture to harden to form said construction material. In a second embodiment, a wadding material comprising the biochar and a method of preparation thereof is disclosed. In a particular embodiment, said wadding material comprising pellets of plaster, clay and/or plastic and the biochar, wherein said pellets are used as fillers in cavities of special interior partition wall panels. The wadding materials were found to be effective in sequestering carbon dioxide from indoor environment.