Characterization of the solid products from hydrothermal liquefaction of waste feedstocks from food and agricultural industries

This study characterized the hydro-char by-product from hydrothermal liquefaction (HTL) of waste feedstocks at two operating temperatures (250 and 300 degrees C) and times (5 and 60 min). The feedstocks were a selection of wastes from: dairy industries (manure and yogurt whey), municipal wastewater treatment plant, dining halls, fruit and alcohol manufacturing and olive oil production. The hydro-char was characterized for mass yield, elemental composition, and Fourier Transform Infrared Spectroscopy (FTIR) coupled with principal component analysis (PCA). The goal was to understand the chemistry and functionalities of the hydro-char, to find alternative niches of applications, and to understand chemical mechanisms undergoing HTL. Results showed that hydro-char can be divided into two different groups regarding mass yield and energy content, based on the pH of the selected feedstocks. In addition, the FTIR-PCA approach was successful to determine specific chemical differences of hydro-char from acid and alkaline feedstocks at different reaction condition.