Environmental implications of power generation via coal-microalgae cofiring

Electrical power plants are responsible for over one-third of the US emissions, or about 1.7 Gt CO2 per year. Power-plant flue gas can serve as a source of CO2 for microalgae cultivation, and the algae can be cofired with coal. The study objective was to conduct a Life Cycle Assessment (LCA) to compare the environmental impacts of electricity production via coal firing versus coal/algae cofiring. The LCA results demonstrate that there are potentially significant benefits to recycling CO2 toward microalgae production. As it reduces CO2 emissions by recycling it and uses less coal, there are concomitant benefits of reduced greenhouse gas emissions. However, there are also other energy and fertilizer inputs needed for algae production, which contribute to key environmental flows. Lower net values for the algae cofiring scenario were observed for the following using the direct injection process (in which the flue gas is directly transported to the algae ponds): SOx, NOx, particulates, carbon dioxide, methane, and fossil energy consumption. Lower values for the algae cofiring scenario were also observed for greenhouse potential and air acidification potential. However, impact assessment for depletion of natural resources and eutrophication potential showed much higher values. This LCA gives us an overall picture and impacts across different environmental boundaries, and hence, can help in the decision-making process for implementation of the algae scenario.