Plant flue gas as a source of CO2 for microalgae cultivation. Economic impact of different process options

As CO2 plays a central role in the economics of microalgae cultivation, an accurate estimate of its cost is essential. Toward this end, an economic model was developed for CO2 recovery from power-plant flue gas and its delivery to microalgae ponds. A design basis was devised for recovering CO2 from flue gas emitted by a typical 500 MW power plant located in the Southwestern United States. For the standard process, which included monoethanolamine (MEA) extraction, compression, dehydration, and transportation to the ponds, a delivered CO2 cost of $40/t was estimated. The model was also used to evaluate the efficacy of directly using the flue gas, however, this option was found to be more expensive. The economics of microalgae cultivation using power-plant flue gas can be evaluated by integrating this model for CO2 recovery with a previously developed model for microalgae cultivation. The model predictions for a long-term process are: a lipid cost of $1.4/gal (unextracted) and a mitigation cost of $30/t CO2 (CO2 avoided basis). These costs are economically attractive and demonstrate the promise of microalgal technology. (C) 1997 Elsevier Science Ltd.