Advanced anaerobic digestion to carboxylic acids

A method comprising:

• utilizing a microorganism for the converting of a substrate to an acid contained in a mixture comprising the acid and water;
• maintaining a pH of the mixture to less than 5;
• and
• treating the mixture with a first stream comprising an organic, wherein:
• the acid is present as a water-soluble species in the mixture,
• the treating results in the transferring of substantially all of the acid from the mixture to the first stream,
• the transferring results in the maintaining of the pH to less than 5, and
• the treating results in the forming of a water stream that is substantially acid-free and a second stream comprising the organic and the acid.