Technology for Producing Biogas and Organic Fertilizers from Bioethanol Industry Waste

Abstract

Introduction. One of the viable approaches to supplementing and partially replacing natural gas is the utilization of biogas. Biogas is produced from organic feedstocks through biomethanogenesis and has a composition comparable to that of natural gas.
Problem Statement. The production of 1 m³ bioethanol generates approximately 10—15 m³ vinasse, a high-strength liquid waste commonly disposed of in filtration fields. Vinasse can serve as a valuable feedstock for biogas production, enabling bioethanol plants to achieve partial energy independence. The capital costs associated with biogas plant installation can be recovered through energy generation and the avoidance of environmental pollution penalties.
Purpose of the Study. The purpose of this study is to develop a biotechnology for the utilization of vinasse in combination with a lignocellulosic co-substrate for the production of biogas and organic fertilizers at bioethanol plants, addressing challenges related to alternative energy supply and waste management in Ukraine.
Materials and Methods. The moisture content was determined by oven drying at 105 ^oC, the ash content by combustion at 550 ^oC, the total nitrogen by the Kjeldahl method, the sulfur content by complexometric titration, and the microelement composition by atomic absorption spectrometry. Vinasse, sweet sorghum bagasse, and digestate have been investigated as substrates for biogas production. Methane fermentation has been studied under mesophilic conditions with periodic loading. Biogas yield has been measured by volumetric displacement of a saline solution and using a Methane Tube. Methane concentration in the biogas has been determined using an automatic gas analyzer and an Agilent 7890B gas chromatograph.
Results. The physicochemical characteristics of native and concentrated vinasse, sweet sorghum bagasse, and digestate as substrates for biogas production have been determined. The combined use of beet vinasse and sweet sorghum bagasse has been shown to increase the abundance of active methanogenic microflora in the bioreactor and to enhance overall process productivity.
Conclusions. A process flow diagram for the production of biogas and organic fertilizers from vinasse and lignocellulosic biomass has been developed, taking into account the current technical and economic conditions of Ukrainian enterprises. The proposed technology demonstrates strong practical potential and can be implemented in alcohol, bioethanol, and sugar production industries.