(380b) Spectroscopic and Thermal Characterization of Carbonized Food Wastes

Waste-to-energy conversion technologies may play an important role to improve the efficiency and sustainability of global food supply. In this worked, performed in collaboration with researchers at UNICAMP (Brazil), we used thermal and spectroscopic methods to characterize the carbonized residues that remain after flow-through hydrothermal extraction and hydrolysis. A recent energy analysis of flow-through hydrothermal hydrolysis finds that it may be energetically favorable compared to other pre-treatment and saccharification techniques. Three factory wastes produced by food industries were studied: sugarcane bagasse, green coffee powder, and defatted coffee cake. We foucs here on results obtained for the coffee wastes. Thermogravimetric analysis (TGA) was used to monitor extraction of semi-volatile components after treatment at 150 °C, followed by hydrolysis and carbonization as temperatures were increased to 250 °C. Infrared spectroscopy indicated that the extracted semi-volatile compounds were a combination of valuable lipids and organic acids. At higher temperatures, infrared spectroscopy identified preferential hydrolysis of hemicellulose components, with cellulose and lignin remaining. Raman microscopy gave further detail, identifying the specific compound chlorogenic acid, a valuable compound marketed as a nutraceutical, as one of the semi-volatile compounds to be extracted from the coffee. At higher temperatures, Raman microscopy provided evidence of carbonization of the coffee waste, as suggested by the appearance of graphitic and defect bands previously associated with hydrothermal char. As shown in the Figure, our results suggest temperature-programmed extraction, hydrolysis, and carbonization of coffee wastes to produce biorefinery streams consisting of valuable organic compounds, bioenergy precursors, and carbonized char.