Operation of a Two-Stage Fermentation Process Producing Hydrogen and Methane from Organic Waste

Abstract

A pilot-scale experimental plant for the production of hydrogen and methane by a two-stage fermentation process was constructed and operated using a mixture of pulverized garbage and shredded paper wastes. Thermophilic hydrogen fermentation was established at 60 degrees C in the first bioreactor by inoculating with seed microflora. Following the hydrogenogenic process, methanogenesis in the second bioreactor was conducted at 55 degrees C using an internal recirculation packed-bed reactor (IRPR). After conducting steady-state operations under a few selected conditions, the overall hydraulic retention time was optimized at 8 d (hydrogenogenesis, 1.2 d; methanogenesis, 6.8 d), producing 5.4 m3/m3/d of hydrogen and 6.1 m3/m3/d of methane with chemical oxygen demand and volatile suspended solid removal efficiencies of 79.3% and 87.8%, respectively. Maximum hydrogen production yield was calculated to be 2.4 mol/mol hexose and 56 L/kg COD loaded. The methanogenic performance of the IRPR was stable, although the organic loading rate and the composition of the effluent from the hydrogenogenic process fluctuated substantially. A clone library analysis of the microflora in the hydrogenogenic reactor indicated that hydrogen-producing Thermoanaerobacterium-related organisms in the inoculum were active in the hydrogen fermentation of garbage and paper wastes, although no aseptic operations were applied. We speculate that the operation at high temperature and the inoculation of thermophiles enabled the selective growth of the introduced microorganisms and gave hydrogen fermentation efficiencies comparable to laboratory experiments. This is the first report on fermentative production of hydrogen and methane from organic waste at an actual level.

Hydrogen Production by Anaerobic Fermentation - General Aspects and Possibility of Using Brazilian Agro-Industrial Wastes

“…138 Devido aos diferentes tempos de retenção hidráulica observados para os processos acidogênicos e metanogênicos, reatores de diferentes dimensões podem ser empregados, levando assim a uma redução do custo do processo. 142 Além disso, estudos têm demonstrado que a separação física dos consórcios acidogênico e metanogênico apresenta uma vantagem em termos de estabilização do processo quando comparada ao sistema de um único estágio para produção de CH 4 , uma vez que o consórcio acidogênico apresenta uma maior capacidade de assimilação de choques de carga orgânica e variações de pH e temperatura. 132,134,140 Estudos na literatura mostram que o processo em dois estágios para produção de H 2 e CH 4 permite uma maior obtenção de energia quando comparado ao processo em um único estágio para produção de CH 4 .…”

Fermentative Hydrogen Production by Molasses; Effect of Hydraulic Retention Time, Organic Loading Rate and Microbial Dynamics

“…Carbohydrate-rich substrates are the most suitable for fermentative H2 production systems (Hawkes et al, 2002;Kapdan & Kargi, 2006;Meherkotay & Das, 2008;Ueno et al, 2007) seeded with saccharoclastic microorganisms, They are able to break down organic substances via the Embden-Meyerhof pathway resulting to different metabolic products depending on the type of microorganism and the environmental conditions driving their catabolism (Hallenbeck, 2009). …”

Hydrogen Fermentation of Cow Manure Mixed with Food Waste

“…Therefore, a two-step treatment (hydrogen fermentation followed by methane fermentation) of organic waste has been proposed 6 . To date, two-step treatments of organic wastes such as food waste 2 , household solid waste 4 and organic solid waste containing paper 12,13 have been reported. Hydrogen fermentation of organic wastes, other than livestock manures, requires the addition of hydrogen-producing bacteria.…”