Title

Optimizing Energy Harvest from Organic Waste Using Hydrogen Producing Biofermentor (HPB) and Microbial Fuel Cell (MFC)

Date of Completion

January 2011

Keywords

Engineering, Environmental

Degree

Ph.D.

Abstract

The increased demand for fossil fuels due to rapid industrialization has resulted in higher energy prices and global warming. The fossil fuel reserves are finite and therefore alternative sources of energy must be investigated. One of the potential energy resources are wastewaters which store substantial chemical energy in form of organic compounds that can be convened for energy generation. However, instead of producing energy from wastewaters, significant energy is spent on wastewater treatment. Another potential energy source is glycerol, which is produced in large quantities as a byproduct of biodiesel production. The conversion of glycerol to bioenergy can be an important value addition to biorefineries. In this study, two technologies namely Hydrogen Producing Bioreactor (HPB) and Microbial Fuel Cell (MFC) are used to optimize energy yields from organic wastewater and glycerol. ^ Microorganisms known as acidogens can convert organic compounds into hydrogen under anaerobic conditions. To optimize hydrogen production from organics, the operational conditions of pH. Chemical Oxygen Demand (COD), Temperature and Hydraulic Retention Time (HRT) were investigated in batch and continuous scale reactors. In a MFC, microorganisms can convert organic compounds into electricity. The bacteria directly transfer electrons to the anode surface through extracellular appendages. ^ The bacterial adhesion to anode was investigated at various stages of biofilm formation and correlated with electricity generation. Moreover bacteria attached on anode surface and bacteria suspended in solution were compared for their contribution to electricity generation. The effect of internal resistance of MFC on energy recovery was investigated. The organic compounds present in the wastewater such as ethanol, acetic and butyric acids were examined at wide range of concentrations for electricity generation.^ The HPB and MFC were operated in series to ensure that contaminants present in HPB effluent were degraded in the MFC, thereby improving the water quality for potential reclamation and enhancing energy recovery. The pure-glycerol and glycerol waste from biodiesel production were examined for value generation in both HPB and MFC. The cometabolism of glycerol with glucose was conducted to enhance hydrogen production. The economic analysis was conducted to examine the benefits of incorporating HPB and MFC in biorefineries for energy and 1, 3-propanediol production from glycerol. ^