A method of pH regulating biomass residues includes the steps of: providing biomass residue comprising solid and liquid parts; exposing the biomass to one or more separation steps, wherein said biomass is separated into one or more solid fractions having a reduced content of water, and one or more fluid fractions; and adding a pH regulator to the biomass residue, and/or the one or more solid fractions, and/or the one or more fluid fractions, wherein the pH regulator comprises a juice derived from agricultural biomass and/or fish manure.