The present disclosure relates to a method for processing a liquid by-product of sodium borohydride hydrolysis to obtain a borate compound, the method comprising the following steps: separating the liquid by-product by sedimentation, to obtain a borate-rich supernatant; drying the borate-rich supernatant under vacuum to obtain a solid composition comprising a borate compound. An aspect of the present disclosure relates composition obtainable by the disclosed method comprising at least 90% (w/w) of sodium boron hydroxide and its use as a source of borate in the production of sodium borohydride and/or hydrogen.