Hydrogen Production During Аnaerobic Fermentation of Corn and Sunflower Waste

Abstract

Background. Obtaining hydrogen – an alternative energy carrier – from renewable resources (agricultural waste). Objective. Establish rational parameters for alkaline pretreatment of sunflower and corn waste by an association of microorganisms to increase the speed of hydrogen production. Methods. We used gas chromatography method to establish the qualitative and quantitative biogas content that was produced during the process of fermentation. We used light microscopy methods to determine lysis zones and to mo­nitor species content of microorganisms association. R esults. We’ve investigated the effect of 5, 10, 20, 30, 40 % alkali concentration during pretreatment of corn and sunflower waste on hydrogen yield in the process of their anaerobic fermentation for 1, 2 and 3 hours. The highest hydrogen yield has been achieved by pretreatment with 20 % NaOH solution for 3 hours. We’ve studied the hydrogen yield during fermentation process with inoculum to culture medium ratio as: 1:6; 1:3; 1:2; 2:3; 1:1 by volume. The content of microorganisms in inoculum was 0.0011 g/cm 3 and the dry residue of culture medium was 0.0267 g/cm 3 . It’s been shown that hydrogen yield in the gas phase reaches 87.5 ± 4.2 % for the association of microorganisms enriched by Clostridium and Bacillus genus with the ratio of inoculum to culture medium 2:3. Fermentation process has been studied in two temperature modes: 22 ± 2 and 35 ± 2 °C. It’s been determined that temperature increase from 22 ± 2 to 35 ± 2 °C increases hydrogen yield by 2 times. It’s been shown that the highest hydrogen yield is observed by holding enzymatic process at pH level near 6–6.5 pH decrease switches metabolic pathways from acetate fermentation type to the formation of butyrate, thus reducing hydrogen yield. Conclusions. The most effective method of substrate pretreatment for the process of obtaining hydrogen by anaerobic fermentation of corn and sunflower waste (1:1) was the pretreatment with 20 % NaOH solution for 3 hours. The highest hydrogen yield has been observed in case of inoculum to culture medium ratio set at 2:3 with pH 6–6.5 and the temperature at 35 ± 2 °C.