Chapter 4 - Optimization of the anaerobic conversion of green biomass into volatile fatty acids for further production of high-calorie liquid fuel

Abstract

The possibility of increasing the concentration of soluble organic substances (up to 44–94 gCOD/L) and reducing sugars (from 1% to 36%) due to the pretreatment of green biomass (straw, sawdust, or lignine), such as acid hydrolysis and oxidative depolymerization, has been studied. At the same time, the enhancement of the acidogenic biocatalyst by the bacteria Clostridium acetobutylicum made it possible to increase the yield of target products, volatile fatty acids (VFAs) and ethanol. It was found that the maximum yield of 27.0% СH3(CH2)2СООН (butanoic acid) and 17.4% С2H5OH (ethyl alcohol) among the studied substrates was obtained in the process of straw conversion. The use of glycerin as a complementary substrate increases the yield of butanoic and ethanoic acids during the conversion of pretreated biomass; with the equimolar addition of glycerin to the straw, the largest yield of butanoic acid was 32.2%. In this case, the yield of VFAs has reached 72.2%.