Process for the production of ethanol and butanol

A process for the production of methane, ethanol and butanol using three separate fermentation steps-comprising:

• a) first fermentation step comprising fermenting initial feedstock to anaerobic fermentation in the presence of acetogenic bacteria, further comprising a mixture of bacterial strains, at a pH below 6.0, at a temperature in the range 20 to 70 degree C., converting said initial feedstock to a product predominantly comprising acetic acid and butyric acid;
• wherein ratio of acetic acid to butyric acid is at least 2:1;
• treating said product predominantly comprising acetic acid and butyric acid to separate a solution comprising the acetic acid and butyric acid by:
• (i) separating residual solids;
• and
• (ii) separating bacteria;
• optionally pasteurizing;
• optionally sterilizing said solution comprising the acetic acid and butyric acid;
• b) second fermentation step comprising fermenting in the presence of solventogenic bacteria said solution comprising the acetic acid and butyric acid from step a) to form ethanol and butanol;
• c) third fermentation step comprising a portion of said feedstock to said first fermentation step is anaerobically digested by a methanogenic bacteria to produce methane;
• optionally a portion of said solution comprising the acetic acid and butyric acid of step a) is anaerobically digested by a methanogenic bacteria in said third fermentation step to produce methane;
• wherein said methane is passed as a fuel gas to a combined heat and power scheme to provide electricity and low pressure steam which are used to meet the energy requirements of the overall process.

A process for the production of methane, ethanol and butanol using three separate fermentation steps-comprising:

• a) first fermentation step comprising fermenting initial feedstock to anaerobic fermentation in the presence of acetogenic bacteria, further comprising a mixture of bacterial strains, at a pH below 6.0, at a temperature in the range 20 to 70 degree C., converting said initial feedstock to a product predominantly comprising acetic acid and butyric acid;
• wherein ratio of acetic acid to butyric acid is at least 2:1;
• treating said product predominantly comprising acetic acid and butyric acid to separate a solution comprising the acetic acid and butyric acid by:
• (i) separating residual solids;
• and
• (ii) separating bacteria;
• optionally pasteurizing;
• optionally sterilizing said solution comprising the acetic acid and butyric acid;
• b) second fermentation step comprising fermenting in the presence of solventogenic bacteria said solution comprising the acetic acid and butyric acid from step a) to form ethanol and butanol;
• c) third fermentation step comprising a portion of said feedstock to said first fermentation step is anaerobically digested by a methanogenic bacteria to produce methane;
• optionally a portion of said solution comprising the acetic acid and butyric acid of step a) is anaerobically digested by a methanogenic bacteria in said third fermentation step to produce methane;
• wherein said methane is passed as a fuel gas to a combined heat and power scheme to provide electricity and low pressure steam which are used to meet the energy requirements of the overall process;
• d) wherein there is also provided, in parallel to the first fermentation step, a gasification step for the production of carbon monoxide and hydrogen from a gasifiable feedstock.