ABSTRACT

A complex study of nonpolluting energy- and resource-saving processing of renewable feedstock with production of methane, ethanol, monosaccharides, biodiesel, and its light analogues is a base for a new technology with multipurpose use of biomass for producing valuable materials for fuel production. Biocatalytic processes with specialized microbe associations play an important role in processing carbohydrate raw materials from agricultural and woodworking wastes, such as straw, sawdust, etc. Biocatalytic methanogenesis is the most widely known process already implemented in practice. This process is complicated by generating additional organic compounds: ethanol, volatile fatty acids (VFAs)—acetic, propionic, butyric acids—toxic for microorganisms generating methane. This undesirable trend has triggered an alternative bioprocess aimed at obtaining the metha- nogenesis byproducts. A selection of microorganisms producing ethanol and VFA was carried out, pH and temperature conditions optimal for their functioning were determined, and the influence of these parameters on the yield and the ratio of biosynthesis products were studied.

Ethanol and VFA are in a low-concentration water solution state during the bioprocess, thus, their extraction method is needed. The best results are obtained by common extraction of ethanol and VFA by halogenated hydrocarbons. This is explained by the generation of ethanol-VFA complexes, more lipophilic than the individual alcohol, the latter being practically impossible to extract from water solutions.

Traditional methods of acid esterification by alcohols include using homogeneous or heterogeneous acid catalysts. Both variants have a number of limitations related to a ratio of reagents, process duration, catalyst type and cost, its removal from reaction sphere, and product purification. Alternative approaches minimizing these problems are being developed in the world. Recently, supercritical fluid (SCF) techniques have gained much attention. Application of SCF considerably enables, up to minutes, reduction in process time, dispenses with the catalyst, and, finally, reduces the total energy consumption.