291598 Closing the Loop: Syngas Production and Nutrient Recycling From Algae
Closing the Loop: Syngas Production and Nutrient Recycling from Algae
Davina Morrow, Anubhuti Lal, Paige Case, Carsten Sievers, Pradeep K. Agrawal, Georgia Institute of Technology, Atlanta, Georgia 30332-0100
A search for alternatives to fossil fuels for chemicals and fuels has become increasingly important. Algae can be used as a feedstock for biofuels and chemicals, but its growth requires a considerable supply of nutrients. Much effort has appeared in the recent literature on utilizing algae for bio-diesel production, but this approach leaves a large fraction of algae unused. In this work, we seek to fully utilize the organic portion of the algae and recycle the inorganic fraction. We have shown that the microalgae Chlorella can undergo pyrolysis and subsequent gasification in CO2 to produce valuable oil and gas products. We also show that the char residue resulting from the pyrolysis at 350⁰C retains 10% more nutrients than char that is gasified at 800⁰C. The gasification of algae at 800⁰C in CO2 is able to yield a significant amount of syngas; however, when gasified at 350⁰C, very little CO and H2 are produced. The gasification step contains most of inorganics present in the host algae. These inorganic species in the char can be effectively extracted in 30% concentrated nitric acid and supplemented as the growth media to successfully produce more algae, completing the cycle. It was shown that DI water extract and 30% nitric acid extracted char at 350⁰C growth mediums grew best.