There is described a process for obtaining a target chemical species, in particular alginate and/or cellulose, from seaweed. The process comprises the steps of: (i) providing a seaweed portion; (ii) bleaching the seaweed portion; and (iii) extracting the target chemical species from the seaweed portion; wherein the bleaching comprises a neutral or alkaline bleaching step, the neutral or alkaline bleaching step comprising using a bleaching composition under neutral or alkaline conditions. The neutral or alkaline bleaching step may precede the extraction step. Also described is alginate, an alginate salt, alginic acid, an alginic acid salt, an alginate derivative, an alginate derivative salt, cellulose, and/or a cellulose derivative obtained by the process.