Demonstration of an Algae-based System for CO2 Mitigation from Coal-fired Power Plants

It is understood that the concentration of global atmospheric carbon dioxide (C02) has increased over time, from approximately 270 ppm at the onset of the Industrial Revolution, to a current value around 390 ppm. This increasing level of C02 is frequently cited as the primary cause of global climate change. For nearly as long as climate change has been debated, strategies have been proposed for mitigating both its global impact and the sources of the CO2 that contribute to it. Many of these suggestions rely on replacement of the primary sources of anthropogenic CO2, namely the burning of fossil fuels for transportation and power production. Despite considerable interest and effort, development of replacements for these fuels remains years in the future, and it is anticipated that these eventual replacements will only offset new, rather than current, fuel needs. Thus, the need for fossil fuels, and more specifically coal for electric power production, will remain significant for the foreseeable future. It is therefore critical for the economic wellbeing of the Commonwealth of Kentucky to seek strategies to alleviate any impact on coal-fired power production stemming from future regulatory or market-driven forces. With direct replacement unlikely, strategies to reduce the emitted C02 are in high demand. The current array of strategies encompasses four main areas: (1) modifications to existing power plants to increase the efficiency of coal combustion, (2) improvements to the efficiency of energy use by consumers, (3) chemical carbon capture with subsequent sequestration, and (4) bio-mitigation with carbon recycling. All of these methods have promise, yet they are beset with significant technical and non-technical challenges. Alterations to the methods of use and production involve issues related to expensive plant modifications or changes to the behavioral patterns of consumers. Despite technological gains for C02 capture and sequestration, the costs associated with energy-intensive C02 concentration and compression are significant and anticipated to result in a parasitic power plant load on the order of 30-40%. Additionally, the uncertainty surrounding risk and liability issues related to long-term geologic sequestration is potentially strong enough to deter investment and adoption. Lastly, the use of microalgae-based bio-mitigation suffers from a range of challenges primarily related to system complexity and scale-up issues that are driven more by economic constraints than technical issues. It should be noted that only biological carbon capture and recycling has the potential to generate a revenue stream to offset, at least in part, the overall cost of implementation. When considerations such as local climate, political and economic constraints, and the geographical location of most coalfired power plants are included, the development of a rational strategy for microalgal carbon capture is even more urgent. Combining these considerations with the abundance of native coal resources and the preponderance of coal-based power generation, the use of microalgae for CO2 mitigation for Kentucky based coal-fired power plants is an attractive option. A conceptual schematic of such a process can be seen in Figure 1.