There is described a process for obtaining a target chemical species, in particular alginate, from seaweed. The process comprises the steps of: (i) providing a seaweed portion comprising a stipe; (ii) removing at least a portion of an outwardly facing surface of the stipe; (iii) dividing the stipe into a plurality of portions; and (iv) extracting the target chemical species from the plurality of stipe portions. The outwardly facing surface of the stipe may be removed by peeling or abrading and the stipe may be divided into a plurality of portions by milling. Also described is alginate, alginic acid or an alginate derivate, or a salt thereof obtained by the process.