Abstract: The present invention relates to production of inorganic fertilizers and biomass fiber suitable for thermal conversion processes. A method of producing biomass fiber for thermal conversion processes and inorganic mineral fertilizer from source biomass, includes mixing size reduced source biomass and a fluid under conditions favorable for extracting inorganic nutrients from the size reduced source biomass. A liquid extract phase and a solid phase are separated from the mixture. The liquid extract phase is then concentrated to obtain the inorganic fertilizer. The solid phase is dried to obtain biomass fiber for thermal conversion processes.