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Vol.2 , No. 1, Publication Date: Aug. 8, 2019, Page: 1-8
 was developed, it makes possible to support high level of methane-production at the high loading rate. In 2-stage anaerobic system different process conditions (such as pH value or temperature) could be adjusted and optimized for the individual groups of microbes in certain degradation steps. Presented paper describes methane production in two-stage solid state anaerobic digestion of plant residuals and chicken dung using lab-scale system. The main objectives of the study were: (1) to examine the influence of temperature regime of hydrolysis stage on whole methane production; (2) to evaluate methane yield in anaerobic digestion of fruit/vegetable waste or hay biomass with a chicken dung; (3) to assess contribution of different stages the digestion into cumulative methane production. All substrates were air dried (at 25-27°C) and well grinded before experiments. Methanogenesis reactors were operated under mesophilic conditions; hydrolysis stages were under mesophilic or thermophilic temperature. Methane production rate and cumulative methane yield was measured separately in hydrolysis and methanogenesis reactors. Total digestion of the substrates at 55°C hydrolysis was in progress 15-17 days; at 37°C hydrolysis – 21-23 days. Methane yield in 2-stage solid state anaerobic digestion of dung/fruit-vegetables waste under 55°C-hydrolysis was 20% higher as against 37°C-hydrolysis (283.5 versus 236 ml CH<sub>4</sub>/gVS); the digestion of dung/hay mixture gave 29% higher methane gas under 55°C-hydrolysis (233 versus 180 ml CH<sub>4</sub>/gVS). It was revealed that the most of total methane gas in 2-stage SS-AD lab-system under ambient pressure was produced in the methanogenesis reactor. A wave-like methane production was observed in hydrolysis reactors, the maximum gas was released in the first day. Periodically, after each 5-7 days the production was stopped and liquid fraction of hydrolysate was withdrawn as a feedstock for methanogenesis reactor. This led to some interruption in the loading of methane-tank and considered as inconvenience for an operation under continuous mode. Integrating of multiple hydrolysis reactors into common system with strong order of loading and withdrawal provides more constant production of feedstock and maintains stable gas production. It is also suggested to accumulate hydrolisates of different withdrawals in one storage unit and mix them before dosed food supply into methanogenesis reactor.&picture=http://www.aascit.org/aascit/decorators/img/journal/804.jpg)
| [1] | Natalya Akinshina, Department of Applied Ecology and Sustainable Development, National University of Uzbekistan Named After Mirzo Ulugbek, Tashkent, Uzbekistan. |
| [2] | Azamat Azizov, Department of Applied Ecology and Sustainable Development, National University of Uzbekistan Named After Mirzo Ulugbek, Tashkent, Uzbekistan. |
Solid-state anaerobic digestion has been widely used to treat various types of organic wastes. Generally, hydrolysis is considered as a rate-limiting step of anaerobic digestion. It tends to produce the higher concentration volatile fatty acids under a high organic loading rate. But, if the concentrations of fatty acids in the single digester are too high anaerobic digestion could be inhibited or failed. That’s why division of whole digestion process into 2 stages (Hydrolysis and Methanogenesis) was developed, it makes possible to support high level of methane-production at the high loading rate. In 2-stage anaerobic system different process conditions (such as pH value or temperature) could be adjusted and optimized for the individual groups of microbes in certain degradation steps. Presented paper describes methane production in two-stage solid state anaerobic digestion of plant residuals and chicken dung using lab-scale system. The main objectives of the study were: (1) to examine the influence of temperature regime of hydrolysis stage on whole methane production; (2) to evaluate methane yield in anaerobic digestion of fruit/vegetable waste or hay biomass with a chicken dung; (3) to assess contribution of different stages the digestion into cumulative methane production. All substrates were air dried (at 25-27°C) and well grinded before experiments. Methanogenesis reactors were operated under mesophilic conditions; hydrolysis stages were under mesophilic or thermophilic temperature. Methane production rate and cumulative methane yield was measured separately in hydrolysis and methanogenesis reactors. Total digestion of the substrates at 55°C hydrolysis was in progress 15-17 days; at 37°C hydrolysis – 21-23 days. Methane yield in 2-stage solid state anaerobic digestion of dung/fruit-vegetables waste under 55°C-hydrolysis was 20% higher as against 37°C-hydrolysis (283.5 versus 236 ml CH4/gVS); the digestion of dung/hay mixture gave 29% higher methane gas under 55°C-hydrolysis (233 versus 180 ml CH4/gVS). It was revealed that the most of total methane gas in 2-stage SS-AD lab-system under ambient pressure was produced in the methanogenesis reactor. A wave-like methane production was observed in hydrolysis reactors, the maximum gas was released in the first day. Periodically, after each 5-7 days the production was stopped and liquid fraction of hydrolysate was withdrawn as a feedstock for methanogenesis reactor. This led to some interruption in the loading of methane-tank and considered as inconvenience for an operation under continuous mode. Integrating of multiple hydrolysis reactors into common system with strong order of loading and withdrawal provides more constant production of feedstock and maintains stable gas production. It is also suggested to accumulate hydrolisates of different withdrawals in one storage unit and mix them before dosed food supply into methanogenesis reactor.
Keywords
Two-stage SS-AD, Co-fermentation, Plant Residuals, Chicken Dung, Methane Production
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