Method for the integrated treatment of waste water

The invention relates to the use of biomethanol from the pulp industry in the production of biohydrogen. The preferred biomethanol comprises purified biomethanol derived from black liquor. The invention also relates to a process for the production of biohydrogen from crude biomethanol recovered from black liquor and to a process for producing hydrocarbon biofuel using such biohydrogen as a hydrogen source. The invention further relates to a biofuel production facility for producing fuel from biohydrogen and biohydrocarbon, and to biofuel so produced. The invention makes it possible to produce a biofuel, wherein 100% of the raw material stems from non-fossil sources.