Sugarcane trash (ST) was converted to ammonium carboxylates using a novel bioprocessing strategy known as long-term air-lime pretreatment/mixed-culture fermentation. At mild conditions (50 degrees C, 5 weeks, 1-atm air, and excess lime loading of 0.4g Ca(OH)(2)/(g dry biomass)), air-lime pretreatment of ST had moderate delignification (64.4%) with little loss in polysaccharides. Without employing detoxification, sterility, expensive nutrients, or costly enzymes, the feedstock (80% treated ST/20% chicken manure) was fermented to primarily ammonium acetate (> 75%) and butyrate by a mixed culture of marine microorganisms at 55 degrees C. In the best four-stage countercurrent fermentation, the product yield was 0.36 g total acids/(g VS fed) and the substrate conversion was 64%. Model predictions indicate both high acid concentrations (> 47.5 g/L) and high substrate conversions (> 70%) are possible at industrial scale. (C) 2010 Elsevier Ltd. All rights reserved.