Influence of the heating rate and the potassium concentration of the feed solution on the hydrothermal liquefaction of used yeast and apple pomace under reducing conditions

Abstract

In the work reported here, baker’s yeast (Saccharomyces cerevisiae), used yeast, and apple pomace were used as feed for the production of liquid biofuels in a continuous one-step process under hydrothermal conditions in the presence of excess hydrogen and K2CO3. The biomass conversion experiments were performed in an up-flow reactor under near-critical water conditions (T 330–450 °C, p 20–32 MPa). The products consisted of three phases: an oil-like organic phase, a gaseous phase, and an aqueous phase. Higher concentrations of organic carbon in the process resulted in a higher product yield. The heating value of the organic phase was up to 37.6 MJ kg−1. Liquefaction of yeast without any addition of K2CO3 also resulted in liquid oil, but the quality and the yield of the oil product were lower. The use of K2CO3 catalyst provides significant effect on the apple pomace conversion process. The carbon mass yield ranged from 270 to 400 g kg−1. Our older statement that the reaction of temperature of 400 °C is optimal for the oil yield and quality has been confirmed with the present new experimental results.