Co-digestion of manure and whey for in situ biogas upgrading by the addition of H2: process performance and microbial insights

Abstract

In situ biogas upgrading was conducted by introducing H(2) directly to the anaerobic reactor. As H(2) addition is associated with consumption of the CO(2) in the biogas reactor, pH increased to higher than 8.0 when manure alone was used as substrate. By co-digestion of manure with acidic whey, the pH in the anaerobic reactor with the addition of hydrogen could be maintained below 8.0, which did not have inhibition to the anaerobic process. The H(2) distribution systems (diffusers with different pore sizes) and liquid mixing intensities were demonstrated to affect the gas-liquid mass transfer of H(2) and the biogas composition. The best biogas composition (75:6.6:18.4) was obtained at stirring speed 150 rpm and using ceramic diffuser, while the biogas in the control reactor consisted of CH(4) and CO(2) at a ratio of 55:45. The consumed hydrogen was almost completely converted to CH(4), and there was no significant accumulation of VFA in the effluent. The study showed that addition of hydrogen had positive effect on the methanogenesis, but had no obvious effect on the acetogenesis. Both hydrogenotrophic methanogenic activity and the concentration of coenzyme F(420) involved in methanogenesis were increased. The archaeal community was also altered with the addition of hydrogen, and a Methanothermobacter thermautotrophicus related band appeared in a denaturing gradient gel electrophoresis gel from the sample of the reactor with hydrogen addition. Though the addition of hydrogen increased the dissolved hydrogen concentration, the degradation of propionate was still thermodynamically feasible at the reactor conditions.

Straw- and slurry-associated prokaryotic communities differ during co-fermentation of straw and swine manure

“…The process enriches microbial consortia that are mainly composed of prokaryotic communities to convert mixtures of organic matter including agricultural, animal, or food waste into biogas with methane content of 50-70 % (Luo and Angelidaki 2013;Town et al 2014). Owing to the improvement of nutrient balance and buffer capacity, a variety of studies have demonstrated the enhancement effect of co-fermentation on the process performance (Ye et al 2013;Ferrer et al 2014).…”

New Steady-State Microbial Community Compositions and Process Performances in Biogas Reactors Induced by Temperature Disturbances

“…The production of biogas via AD is a complex process, involving many different microbial species [2]. The complex organic compounds are first hydrolyzed into oligomers and monomers, and then further converted to acetate, CO 2 , and H 2 by various fermenting bacteria. The methanogenesis is the final step to convert acetate, CO 2 , and H 2 to CH 4 by methanogenic archaea.…”

“…The complex organic compounds are first hydrolyzed into oligomers and monomers, and then further converted to acetate, CO 2 , and H 2 by various fermenting bacteria. The methanogenesis is the final step to convert acetate, CO 2 , and H 2 to CH 4 by methanogenic archaea. The syntrophic relationship between bacteria and archaea is essential for the stability of the biogas process [3].…”

Proceedings of the 58th Conference on Simulation and Modelling (SIMS 58) Reykjavik, Iceland, September 25th – 27th, 2017

“…These methods are performed outside of the anaerobic reactor for biogas upgrading which requires extra investments. Previous studies have shown that CH4 in AD can be increased by adding inorganic electron donors such as H2 and CO (Luo & Angelidaki, 2013). These can, for example, be produced as syngas from wood through a gasification process.…”

“…Hydrogen can be used to upgrade the methane production directly in the reactor by increasing the hydrogenotrophic methanogenesis (Luo & Angelidaki, 2013), which consumes hydrogen together with CO2 in the biogas, with methane as product (Luo & Angelidaki, 2012):…”