Biohydrogen production in the two-stage process of anaerobic bioconversion of organic matter of liquid organic waste with recirculation of digister effluent

At present, hydrogen energy is gaining immense popularity in the world due to the problem of depletion of non-renewable energy sources, hydrocarbons, and environmental pollution caused by their growing consumption. Of particular interest is the dark process of producing hydrogen-containing biogas in the processing of organic waste under anaerobic conditions which allows to take advantage of both energy production and solving the problem of recycling organic waste. The article describes in detail an experimental plant for investigating a two-stage process of anaerobic bioconversion of organic matter of liquid organic waste and setting up an experiment to study the effect of recirculation of the methantenk effluent into an anaerobic bioreactor for the production of biohydrogen. Moreover, experimental studies were carried out in a continuous mode in reactors with increased volume. The average specific yield of biohydrogen (per kilogram of initial organic matter (OM)) during recirculation of the methantenk effluent increased by 4% (from 0.1046 to 0.1087 m(3)/(day * kg of OMin)). In addition, recirculation of the methantenk effluent to the biohydrogen production reactor during two-stage anaerobic bioconversion allowed us to reduce fluctuations in the output of biohydrogen from the reactor. At the same time, there was no methanogenic activity in the anaerobic bioreactor for the production of biohydrogen. The self-stabilizing pH level in the anaerobic bioreactor for producing biohydrogen was less than 4.5 (3.94 without effluent recirculation and 3.88 with recirculation), however, there was no inhibition of hydrogen formation. Thus, the use of recirculation of the methantenk effluent into the anaerobic bioreactor for producing biohydrogen can enhance the efficiency of the two-stage anaerobic bioconversion of organic waste while maintaining the stability of the process. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.