Effect of liquid digestate recirculation on biogas production and enzyme activities for anaerobic digestion of corn straw

Abstract

To accelerate the degradation of substrate, 50% liquid digestate recirculation (LDR) was used in the anaerobic digestion (AD) of corn straw. The effects of recirculation on the enzyme activities and biogas production were investigated by comparing with control reactor (ReactorCK). During the AD process the fermentation system with 50% LDR was more stable. The average biogas and methane production in ReactorLDR were 7,891 mL·d−1 and 347 mL CH4·g−1 VSadded·d−1 respectively. The total volatile fatty acids (TVFAs) concentration in two reactors both increased at first and then decreased with time. And the LDR made the VFAs accumulation significant, especially propionic acid accumulation in 4 ∼ 16 days. The maximum peak value of cellulase, xylanase, dehydrogenase and coenzyme F420 activities in ReactorLDR were 0.51 mg·g−1·h−1, 0.29 mg·g−1·h−1, 4.88 mL·g−1·h−1 and 6.69 μmol·L−1, respectively, which were higher than that in ReactorCK. With or without recirculation, the concentration of TVFAs was positively correlated with cellulase, xylanase and dehydrogenase activities, while was negatively correlated with coenzyme F420 activity. Besides, a very significant correlation existed between hydrolase and dehydrogenase activities and daily biogas production in ReactorCK. And the peaks of cellulase, xylanase and dehydrogenase activities were appeared ahead of the peak of daily biogas production with the LDR.

Peering into a Simplified Digestor for Households: Performance, Cost and Carbon-Neutral Niche

“…In practice, the liquid digestate from the digestor could be returned and formed liquid digestate recirculation, which has been proven effective in biogas promotion by improving the buffer capacity and stability of the digestion system and further increasing the hydrolysis and fermentation microorganism population. A biogas rate 33.3% higher than the maximum volume was achieved by 50% of the digestate being recircled to the digestor in a lab-scale study, and liquid digestate recirculation was also influential in a two-phase digestor system [17,18]. It was detected that about 50% of the biogas was produced from the returned liquid digestate [16].…”

“…Thus, dilution of the raw substrate is required to avoid clogging, and adding water to dilute is a common strategy but enlarges the digestor volume and digestate amount [14,15]. Liquid digestate recirculation has been proven to be productive in biogas production and substrate dilution as well [16,17]. Using digestate instead of water for manure dilution can be an option, but only limited information is available [18].…”

“…What is more, reusing liquid digestate could downsize the net slurry discharge, lowering pollution loading to the downstream disposal units. Digestate has been reported to be environmentally hazardous due to the high concentration of oxygen-consuming content, defined as chemical oxygen demand (COD) [17,18]. Disposal via decontamination and stabilization is required before discharging slurry to the receiving water, generally including solid-liquid pre-separation, reduction of the solid fraction and biological treatment of the liquid fraction [19].…”

Performance of Zeolite and Trace Elements on Biogas Production from Alkaline Hydrogen Peroxide–Pretreated Sweet Sorghum Bagasse Slurry

“…Dehydrogenase, as an important REDOX enzyme, will activate hydrogen ions of oxidized organic matter and transfer them to speci c hydrogen receptors. Dehydrogenase activity level is an important index of the average activity of microbial metabolic active population in anaerobic digestion [39]. According to Fig.…”

Biogas Production and Metagenomic Analysis in a New Hybrid Anaerobic Labyrinth-Flow Bioreactor Treating Dairy Wastewater

“…This construction provided longer biomass retention time, lower sludge yield, the ability to partially separate acidogenesis and methanogenesis, better resilience to hydraulic and organic shock loadings, and better substrate accessibility to methanogens, consequently resulting in high treatment efficiencies at low HRT (2-6 h) and high OLR (0.4-28 kg/m 3 •d) as well as increasing the overall stability of the reactor. According to the literature, recirculation provides some benefits during wastewater treatment, such as improving contact between the methanogenic bacteria and substrate components, greater reactor homogeneity, and shortening the time in which maximum methane yield is achieved [54,55]. Recirculation of the digestate liquid fraction within the anaerobic digester is mostly used in dry anaerobic digestion [54,[56][57][58].…”