Carbon dioxide is the most dominant component of greenhouse gases and its increasing level in the atmosphere has been of growing concern for many years. There have been many methods to reduce carbon dioxide emissions in the form of CO 2 capture and storage, for example, through its injection into underground waters, saline waters or aquifers in which, CO 2 is transferred from one place to another. However, with these approaches there is always the risk of CO 2 release to the environment.  In this research, a new method for capture and conversion of carbon dioxide in an anaerobic system with an UASB (Upflow Anaerobic Sludge Blanket) reactor (1 L working volume) at 35{493}C is developed. Acetic acid and mixed VFAs (Volatile Fatty Acids) were tested as sources of hydrogen. The system performance was evaluated based on CO 2 and COD (Chemical Oxygen Demand) removals. Values of 68.7%-85.78% were obtained for CO 2 removal and the overall efficiency values were above 50% for loading rates up to 25 gCOD/L.d with a high methane content (>70%) in the biogas. (Abstract shortened by UMI.)