Pyrolysis Decomposition Analysis of Wastewater Derived Microalgae Via TGA-FTIR

Cultivation of wastewater microalgae suggests a sustainable path to the development of renewable fuels due to algae’s high productivity, mitigation of green house gases and utilization of non-drinkable water. However, due to variable concentrations of macro-nutrients in municipal wastewater and extensive diversity of microorganisms cultivated, a biochemical characterization of mixed-culture microalgae is still needed. This study utilizes a combined application of Thermogravimetric Analysis (TGA) and Fourier Transform Infrared Spectrometry (FTIR) to analyze the pyrolitic decomposition of algae qualitatively and potentially quantitatively. Algae are pyrolyzed for 30 minutes at the individual decomposition temperatures identified through derivative TGA (DTG) curves and the residual char is analyzed via FTIR spectroscopy. The IR spectra of the pyrolyzed biomass and the initial algae provide a qualitative comparison of the biochemical constituents present in the biomass after pyrolytic conversion.  The step-wise decomposition of algae indicates distinct losses of functional groups.  These include amide I & II peaks (~1650 cm^-1and ~1515 cm^-1, respectively) and N-H peak (~3300cm^-1) associated with proteins as well as P=O peak (~1225 cm^-1) and CH₂ and CH₃ peaks (~2920 cm^-1 and ~2850 cm^-1, respectively).  Similar analysis is performed on algae of different growth conditions performed during cultivation at Lawrence, KS Municipal Wastewater Treatment Plant.