TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Components: The product stream has a concentration of acetic acid in solution of 2-5 wt.% and a concentration of butyric acid in solution of 0.2-0.75 wt.%. The acetic acid and butyric acid are present in a combined concentration of at least 60 wt.%, preferably at least 90 wt.% of the total weight of carboxylic acids in the product stream, and the product stream comprises at least a 2:1, preferably 4:1 ratio of acetic acid to butyric acid. The ethanol and butanol stream from step (d) has a concentration of ethanol in solution of 2-5 wt.% and a concentration of butanol in solution of 0.2-0.75 wt.%. The mixture of bacterial strains includes at least some of the bacteria present in the biomass feedstock. The solventogenic bacteria are Clostridium acetobutylicum, C. beijerinckii, C. aurantibutyricum or C. tetanomorphum. The biomass is landfill leachate. Preferred Method: The pH in step (b) is maintained below 6.0. The temperature in step (b) is 40-70 degrees C. The step (c) comprises: filtration to remove any residual solids. A portion of the biomass feed to the first fermentation step or a portion of the feed to the second fermentation step is, instead, passed to a third fermentation step where it is anaerobically digested by a methanogenic bacteria to produce methane. The 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. EXAMPLE - Municipal solid waste as a biomass feedstock was pre-treated to make it suitable for anaerobic digestion. Then the feedstock was pre-heated and fed to a continuous fermentation vessel containing a mixture of acid-producing anaerobic bacteria. The pH was maintained at 6 and the temperature was maintained at about 55 degrees C to increase acetic acid production rather than carboxylic acids and to inhibit methanogenesis. The fermented broth containing 2-5 wt.% of acetic acid, 0.2-1 wt.% of butyric acid and small amount of carboxylic acid was filtered to remove residual solids. The broth was pasteurized by heating to 72 degrees C. The broth was then passed to a second fermentation vessel. In the second fermentation, the carboxylic acids were converted to relevant alcohols of the same number of carbon atoms using the bacterial Clostridium acetobutylicum. The product from this step contained 2-5 wt.% of ethanol, 0.2-1 wt.% of butanol and smaller amounts of other alcohols was filtered to remove any solids and column. The filtrate was heated and fed to a distillation column. A liquid product containing about 40 wt.% of butanol was removed as a side draw from the column. A liquid product containing about 94 wt.% of ethanol was from just below the top of the column.