Thermo-Economic Analysis of Microalgae Co-Firing Process for Fossil Fuel-Fired Power Plants

A thermoeconomic analysis of microalgae co-firing process for fossil fuel-fired power plants is studied. A process with closed photobioreactor and artificial illumination is evaluated for microalgae cultivation, due to its simplicity with less influence from climate variations. The results from this process would contribute to further estimation of process performance and investment. The concept of co-firing (coal-microalgae or natural gas-microalgae) includes the utilization of CO₂ from power plant for microalgal biomass culture and oxy-combustion of using oxygen generated by biomass to enhance the combustion efficiency. As it reduces CO₂ emission by recycling it and uses less fossil fuel, there are concomitant benefits of reduced GHG emissions. The by-products (oxygen) of microalgal biomass can be mixed with air or recycled flue gas prior to combustion, which will have the benefits of lower nitrogen oxide concentration in flue gas, higher efficiency of combustion, and not too high temperature (avoided by available construction materials) resulting from coal combustion in pure oxygen. Two case studies show that there are average savings about $0.386 million/MW/yr and $0.323 million/MW/yr for coal-fired and natural gas-fired power plants, respectively. These costs saving are economically attractive and demonstrate the promise of microalgae technology for reducing greenhouse gas (GHG) emission.