IX Международная студенческая научная конференция Студенческий научный форум - 2017

Nowadays, anaerobic digestion processes for agricultural wastes are world widely utilized to reduce environmental and social issues in the areas of livestock and poultry farms, and it has become an alternative way of renewable energy production. Numerous studies had been conducted in order to increase and stabilize biogas yield, optimize anaerobic biogas technologies. One of the ways of optimization of biogas production is improvement of bioreactors design. Since successful application of anaerobic fermentation technologies for treatment of organic waste from agricultural and industrial production is largely dependent on the development and use of high-rate anaerobic bioreactors. In such reactors, a large amount of substrate is processed, and optimally designed bioreactor can reduce processing time and improve the processing efficiency, resulting in an overall reduction in processing cost [1].

In this present paper we give results of investigation of the performance of single-stage leach-bed reactor for treatment of solid cattle manure, concentrating on the biogas production and composition. Experiments were conducted in bioreactor with a working volume of 50 L which had been constructed by modifying leach-bed reactor and fixed-bed reactor for anaerobic digestion of cattle manure. Full characteristics of the experimentdl set-up are given in Korazbekova et al. (2013) [1]. Fresh material (FM) as received and inoculum samples were analyzed in triplicate according to standard methods of APHA (1995) [2]. Accordance with results of tested substrate analysis, DM content of cattle manure was 25.93% and 84.07% of solids were oDM.

Results of cumulative biogas production are shown in Fig. 1. The rapid initial biogas production was due to readily biodegradable organic matter and presence of high content of the methanogens. The biogas generation started after inoculating, kept increasing until reaching the peak, and then began to decline (Li et al., 2011) [3]. Run 1 showed the maximum biogas production on day 4 in the amount of 0.032 Nm³(kg oDM)^-1 and daily biogas generation was observed more than 0.018 Nm³(kg oDM)^-1 between days 2 and 10, reduced to less than 0.005 Nm³(kg oDM)^-1 after day 19. The cumulative biogas yield was indicated as 0.327 Nm³(kg oDM)^-1 at the end of Run 1. Biogas production started faster in Run 2, i.e. peak biogas generation (0.047 Nm³(kg oDM)^-1) was achieved up to day 3 of the experiment demonstrating the maximum degree of biogas formation till days 9 (daily production more 0.02 Nm³(kg oDM)^-1) and intensive metabolism of microorganisms, since reactor was enriched with methanogens because of biofilm formation and use of fermented leachate from previous run. The cumulative biogas production was 0.328 Nm³(kg oDM)^-1 at the end of 21-day of HRT. There were not observed several peaks during the digestion process in both two runs as reported by Li et al. (2011) [3; 4].

Fig. 1: Cumulative biogas production

Final data of biogas production showed that, (0.331±0.005) Nm³(kg oDM)^-1 biogas (standard error = 0.003) with an average percentage of methane (47.13±1.40)% was obtained during the anaerobic fermentation of cattle manure in the reactor with immobilization device.

In conclusion, dry fermentation of cattle manure with dry matter content of 25.93% in leach-bed reactor without anaerobic pretreatment and mixing is feasible and stable process for production of biogas from agricultural wastes. Immobilization of methanogens on the supporting materials (polyethylene packing rings) in leach-bed reactor improved biogas production.

References

1. Korazbekova K.U., Bakhov Zh.K., Saparbekova A.A. Dry Fermentation of Agricultural Waste in the Modified Leach-bed Reactor with Immobilization of Microorganisms // Biotechnology. – 2013. – Vol. 12(6). - P. 236-244.

2. APHA. Standard Methods for the Examination of Water and Wastewater. - Washington DC, 1995. – 53 p.

3. Li J., Jha A.K., He J., Ban Q., Chang S., Wang P. Assessment of the effects of dry anaerobic co-digestion of cow dung with waste water sludge on biogas yield and biodegradability // International Journal of the Physical Sciences. – 2011. – Vol. 6(15). - P. 3723-3732.

4. Deublein D., Steinhauser A. Biogas from Waste and Renewable Resources. - Germany, 2008. - 423 p.

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