Identifying proper agitation interval to prevent floating layers formation of corn stover and improve biogas production in anaerobic digestion

Tian, Libin; Zou, Dexun; Yuan, Hairong; Wang, Linfeng; Zhang, Xin; Li, Xiujin

doi:10.1016/j.biortech.2015.03.018

Cited by 37 publications

(12 citation statements)

References 25 publications

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“…RS, like other lignocellulosic substrates, has a complex chemical structure. RS also has some specific physical characteristics like low density, high water holding capacity, poor fluidity, and heterogeneity [87,92]. RS floats on the surface in the digester and does not mix properly, especially when biogas is entrapped in the slurry.…”

Section: Mixingmentioning

confidence: 99%

“…RS floats on the surface in the digester and does not mix properly, especially when biogas is entrapped in the slurry. Due to poor mixing, the substrate does not get good contact with the microorganisms, thus reducing degradation and, ultimately, lowering biogas yield [92].…”

Section: Mixingmentioning

confidence: 99%

“…It was higher than that of other stirring rates by about 19% (40 rpm), 10% (120 rpm), and 12% (160 rpm). Tian et al [92] utilized the results of Shen et al [87] for identifying proper agitation intervals to prevent floating layer formation during AD of corn stover (CS) and to improve the biogas yield. Shen et al [87] studied the effect of various stirring rates (40,80,120, and 160 rpm for 5 min each time) on biogas yield of RS, while Tian et al [92] further investigated the effect of various agitation intervals (continuous; after 2, 4, 8, and 12 h for 5 min for each time) with different OLRs (1.44, 1.78, and 2.11 g TS L −1 d −1 ) on the biogas yield from AD of CS in CSTRs.…”

Section: Mixingmentioning

confidence: 99%

“…Tian et al [92] utilized the results of Shen et al [87] for identifying proper agitation intervals to prevent floating layer formation during AD of corn stover (CS) and to improve the biogas yield. Shen et al [87] studied the effect of various stirring rates (40,80,120, and 160 rpm for 5 min each time) on biogas yield of RS, while Tian et al [92] further investigated the effect of various agitation intervals (continuous; after 2, 4, 8, and 12 h for 5 min for each time) with different OLRs (1.44, 1.78, and 2.11 g TS L −1 d −1 ) on the biogas yield from AD of CS in CSTRs. The results of the study showed that, at lower OLR of 1.44 g TS L −1 d −1 , there was no floating layer observed in the digesters when the time interval for the agitation was continuous for 2 h, 4 h, and 8 h, while the performance of AD was adversely affected at 12 h. Moreover, the biogas yield for the digester agitated after 12 h was 418 L/kg TS, which was 2%, 9%, 3%, and 0% lower than those digesters stirred continuously, for 2 h, 4 h, and 8 h, respectively.…”

Section: Mixingmentioning

confidence: 99%

“…Numerous bench-scale experiments have been carried out on RS digestion to define the optimal temperature [25,26,42], substrates for co-digestion [39,65,66], mixing intensities and duration [87,92], OLR [28,40,41], sources of inoculum [38], S/I ratio [69], recycling LD to the digester [36,98], addition of TEs and their bioavailability [110]. Bench-scale studies are important to understand the principles but it is challenging to design and operate a farm-scale plant based on these microcosms [124].…”

Section: Pilot-scale and Farm-scale Plants For Ad Of Rsmentioning

confidence: 99%

See 4 more Smart Citations

A Review on the Fate of Nutrients and Enhancement of Energy Recovery from Rice Straw through Anaerobic Digestion

2020

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Open field burning and tilling the rice straw (RS) back into the fields causes environmental threats by contributing to the increased greenhouse gas emissions. Energy and nutrient recovery from RS through anaerobic digestion (AD) is an effective solution for its utilization. Although RS has good methane potential, its characteristics make it a difficult substrate for AD. This paper reviews the characteristics of RS, mass balance, and distribution of nutrients into liquid and solid digestate in the AD. The present review also discusses the effect of temperature, co-digestion, mixing, inoculum, organic loading rate, recycling liquid digestate, the addition of trace elements, and their bioavailability on the enhancement of biogas/methane yield in the AD of RS. In addition, the digestion of RS at various scales is also covered in the review.

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Section: Mixingmentioning

confidence: 99%

Section: Mixingmentioning

confidence: 99%

Section: Mixingmentioning

confidence: 99%

Section: Mixingmentioning

confidence: 99%

Section: Pilot-scale and Farm-scale Plants For Ad Of Rsmentioning

confidence: 99%

See 3 more Smart Citations

A Review on the Fate of Nutrients and Enhancement of Energy Recovery from Rice Straw through Anaerobic Digestion

2020

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Characterization of Mechanically Pretreated Wheat Straw for Biogas Production

2020

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Biogas production from wheat straw is one strategy of converting biomass to bioenergy, but pretreatment of the lignocellulosic material is necessary in order to render the substrate biodegradable. In this study, four different mechanical pretreatments of wheat straw were investigated: roll milling, extrusion, pelletization, and hammer milling. The effects of the pretreatments on anaerobic digestion (AD) at 37°C and on enzymatic hydrolysis (EH) with Cellic CTec2 at 50°C were analyzed in terms of biochemical methane potential (BMP), maximum daily methane production (DMPmax), and EH yield as amount of released glucan/initial glucan content. Roll milling generated the highest BMP of 287 NmL CH 4 gVS −1 , an increase of 21% compared with untreated wheat straw. Extrusion provided the highest methane production rate (52 NmL CH 4 gVS −1 day −1), the lowest floating capacity, and a high bulk density. It was further concluded that a linear relationship exists between the DMPmax and the EH yield (R 2 = 0.768) which for roll-milled size fractioned wheat straw was even stronger (R 2 = 0.900) but weaker for mechanically pretreated non-size fractioned straw (R 2 = 0.625). Specific surface analysis and EH of 0.25-1-mm particles revealed that mechanical pretreatment most likely affect other physiochemical properties in wheat straw, such as the crystallinity or melting of the outer wax layer, which in turn affects AD and EH processes differently.

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Characterization of Mixing by CFD Simulation and Optimization of Mixing Frequency to Break Scum and Enhance Methane Yield in Chinese Dome Digester

et al. 2022

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The Chinese dome digester (CDD) is a low-cost and the most popular anaerobic digester that is used for the treatment of organic waste such as food waste and cow dung. However, the main challenge of CDD is scum formation due to inadequate mixing intensity. This study explores computational fluid dynamics (CFD) to characterize mixing in CDD and the effects of mixing frequency (0, 4, 6, and 8 times per day) on the performance of semicontinuous anaerobic digestion to break scum and enhance methane yield. The flow field simulation on a lab-scale CDD by Ansys Fluent (v.19.2), a finite volume solver, estimated that 45% of CDD working volume was occupied by dead zones which could nurture scum. The simulation results elicited the optimization of mixing frequency. Four CDDs were operated to investigate the optimum mixing frequency. The average scum thickness for the non-mixed digester was 2 ± 0.1 cm compared to 0.2 ± 0.1, 0.8 ± 0.1, and 1.3 ± 0.2 cm for the mixed digesters (4, 6, and 8 times per day, respectively). The average methane yields for 0, 4, 6, and 8 times per day were 206 ± 191, 602 ± 87, 555 ± 59, and 492 ± 109 mL g-VS−1, respectively. Four times per day was the optimum mixing frequency and the energy required to break scum was 6.1 ± 0.3 Joules per mixing cycle. This study proves that by optimizing the mixing frequency in CDD, scum formation can be controlled without additional investment cost.

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Identifying proper agitation interval to prevent floating layers formation of corn stover and improve biogas production in anaerobic digestion

Cited by 37 publications

References 25 publications

A Review on the Fate of Nutrients and Enhancement of Energy Recovery from Rice Straw through Anaerobic Digestion

A Review on the Fate of Nutrients and Enhancement of Energy Recovery from Rice Straw through Anaerobic Digestion

Characterization of Mechanically Pretreated Wheat Straw for Biogas Production

Characterization of Mixing by CFD Simulation and Optimization of Mixing Frequency to Break Scum and Enhance Methane Yield in Chinese Dome Digester

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