A method of producing a fertiliser composition, the method comprising: (a) providing partially decomposed organic matter (e.g. cellulose fibres); (b) contacting the organic matter with:(i) an anaerobic digestate;(ii) a source of nitrate ion;(iii) a source of ammonia; and (c) contacting the mixture obtained in step (b) with a source of carbon dioxide. The aim is to reduce waste and to reduce emissions of carbon dioxide.
