Analysis and Comparison of Bio-Oils Obtained by Hydrothermal Liquefaction of Organic Waste

Abstract

This paper presents an analysis of bio-oil quality depending on the type of input biomass, the process conditions and the catalytic systems used. Analysis of various catalytic system choices showed the prospects of using nickel and iron metal salts as homogeneous catalysts given that their use provided increases of 24.5% and 22.2%, respectively, in the yield of light-boiling bio-oil fractions (with a boiling point of up to 350 °C). Composition analysis of the bio-oils carried out using gas chromatography and nuclear magnetic resonance spectroscopy showed that fatty acids are the predominant group of substances in bio-oils produced from sewage sludge. Bio-oil synthesized from bark and wood waste contains phenolic alcohols and a limited range of cyclic hydrocarbons as the main components. In bio-oil produced from macroalgae, oxygen and nitrogen compounds of the piperazinedione and amides type are predominant. The sulfur and nitrogen content in all types of bio-oils is at an acceptable level. The results allow researchers to assert that organic waste processing enables production of sufficiently high-quality fuel, which can then be jointly processed with natural oil. Bio-oil produced from secondary sludge has the best quality, characterized by a high content of low-weight aliphatic compounds (with a boiling point of up to 350 °C), along with insignificant levels of nitrogen, sulfur and oxygen.