This study is based on the production of carboxylic acids through the anaerobic digestion of biomass.  In the MixAlco^™ process, carboxylic acids are neutralized with calcium carbonate to form carboxylic salts that can be chemically upgraded to higher alcohols liquid biofuel. In this study, Algaefiber^®, an alkaline pretreated waste biomass from seaweed processing (FMC Biopolymer), was used as the biomass source.  Algaefibers^® derived from red seaweeds (Eucheuma spinosum and Gigartina radula) were anaerobically digested using a mixed culture of marine-derived microorganisms in bench scale batch fermenters at mesophilic and themophilic temperatures (35⁰C and 55⁰C respectively). The acidogenic digestion and suppression of methanogenesis were achieved by adding small doses of iodoform.  Calcium carbonate and ammonium bicarbonate were added to the fermenters to maintain the pH above 6.  The produced carboxylic acids ranged from 2 to 7 carbons.  The total carboxylic acid production was found to be higher at lower temperature. Acetic acid was the prominent acid at both temperatures but the proportion of acetic in the mixture was greater at thermophilic temperature.