NOVELTY - Obtaining product containing 6C and/or 8C carboxylates and/or methane from carbohydrate containing biomass, comprises: contacting carbohydrate containing biomass, alcohol, and mixture of microorganisms in vessel (103) to form reaction mixture; maintaining reaction mixture under anaerobic conditions at 15-40 degrees C, pH of 4-6, and hydrogen partial pressure of 0.2-5 atmospheres so that 6C and/or 8C carboxylates and/or methane are formed in reaction mixture; and separating at least portion of 6C and/or 8C carboxylates and/or methane from reaction mixture to obtain product.    USE - The method is useful for obtaining a product comprising 6C and/or 8C carboxylates and/or methane from a carbohydrate containing biomass.    ADVANTAGE - The method provides: less than 5% loss of input carbon as carbon dioxide (claimed); removal of the 6C and/or 8C carboxylates continuously or in-line, which doe not inhibit methanogenesis; and the 6C and/or 8C carboxylates and methane with high yield, which provide potential cost and energy savings.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a system (100) for producing 6C and/or 8C carboxylates from a reaction mixture, comprising: a vessel for containing the reaction mixture under anaerobic conditions, where the vessel has an entrance orifice (106) for receiving components of the reaction mixture, and an exit orifice (109) for removing fluid from the vessel; a control valve (112) in pneumatic communication with a headspace of the vessel and configured to maintain a hydrogen partial pressure within the headspace of 0.2-5 atmospheres; a pH controller configured to maintain a pH of the reaction mixture of 4-6; and a separation device configured to receive a carboxylate-containing fluid from the vessel by way of the exit orifice, separate at least a portion of the 6C and/or 8C carboxylates from the received fluid, and return the remainder fluid to the vessel by way of the entrance orifice.    DESCRIPTION OF DRAWING(S) - The figure shows a diagram of a system.    System (100)    Vessel (103)    Entrance orifice (106)    Exit orifice (109)    Control valve (112)