Feasibility and performance of high-rate psychrophilic dry anaerobic digestion of high solids content dairy manure (original) (raw)
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Anaerobic digestion of cattle manure: effect of phase-separation
Energy and Sustainability III, 2011
Various aspects of anaerobic digestion (AD) technology have been the focus of research in recent years. Shortening the digestion time with enhanced process efficiency is one of the integral concerns in AD technology. This study was conducted to investigate the feasibility of a two-phase anaerobic treatment system for unscreened dairy manure. Hydraulic retention time (HRT) and organic loading rate (OLR) in the hydrolytic reactor are varied in order to evaluate the effect of these factors. The results showed that an optimum HRT and OLR of 2 days and 15 g.VS/L.day, respectively, yielded maximum acidification. The separation of acidogenic and methanogenic phases of digestion resulted in a significant increase in methane production rate in the methane reactor. The methane yields were found to be 313 and 221 mL CH 4 /g.VS loaded in two-phase and one-phase systems at 35°C, respectively.
Mesophilic–thermophilic–mesophilic anaerobic digestion of liquid dairy cattle manure
Water Science & Technology, 2006
The potential of a mesophilic -thermophilic -mesophilic anaerobic digestion system was investigated with respect to improvement of both digestion and sanitation efficiencies during treatment of liquid cattle manure. The pilot plant produced a high methane yield from liquid dairy cattle manure of 0.24 m 3 (kg VS fed ) 21 . Considering the low system loading rate of 1.4-1.5 kg VS (m 3 d) 21 , digestion efficiency compared to conventional processes did not appear improved. The minimum guaranteed retention time in the tubular thermophilic reactor was increased compared to a continuously stirred tank reactor. Levels of intestinal enterococci in raw liquid manure as determined with cultivation methods were reduced by 2.5 -3 log units to a level of around 10 2 cfu/mL. This sanitizing effect was achieved both during mesophilic -thermophilic -mesophilic and thermophilic -mesophilic treatment, provided the thermophilic digester was operated at 53 -558C. A change in feeding interval from 1 h to 4 h did not significantly alter methane yield and sanitation efficiency. It was proposed that a two-stage, thermophilic -mesophilic anaerobic digestion system would be able to achieve the same sanitizing effect and equal or better digestion efficiency at lower costs.
The anaerobic digestion of cattle manure: the effect of phase-separation
WIT transactions on state-of-the-art in science and engineering, 2014
Various aspects of anaerobic digestion (AD) technology have been the focus of research in recent years. Shortening the digestion time with enhanced process efficiency is one of the integral concerns in AD technology. This study was conducted to investigate the feasibility of a two-phase anaerobic treatment system for unscreened dairy manure. Hydraulic retention time (HRT) and organic loading rate (OLR) in the hydrolytic reactor are varied in order to evaluate the effect of these factors. The results showed that an optimum HRT and OLR of 2 days and 15 g.VS/L.day, respectively, yielded maximum acidification. The separation of acidogenic and methanogenic phases of digestion resulted in a significant increase in methane production rate in the methane reactor. The methane yields were found to be 313 and 221 mL CH 4 /g.VS loaded in two-phase and one-phase systems at 35°C, respectively.
Detritus
Treating organic solid wastes economically is a challenge, predominantly in cold and high-altitude regions. Objective of this research was to determine the operating strategies to reduce the start-up phase of high-solid anaerobic digestion (HSAD) process and to improve the digestion of food waste (mainly fruits and vegetable wastes [FVW]) with or without animal manure in a low-cost AD system at 20-25°C. In addition, this study aimed to obtain the basic design criteria for starting up of scaled-up HSAD system using adapted liquid inoculum. Inoculum to feedstock ratio was varied from 6:1 to 3:1. The organic loading rate (OLR) expressed as volatile solids (VS) and operational cycle length was varied from 0.44-2.1 Kg VS Kg inoculum-1 d-1 and 33-14d, respectively. Obtained results show that methane (CH 4) production from FVW was feasible at low-to-moderate temperature and specific methane yield of 0.4-0.6 L g VS-1 was observed even at high OLR. CH 4 conversion rates and its quality were not affected, while maintaining the operational stability (e.g. no acidification or VFA accumulations). CH 4 content reached over 60% and remained almost steady. Results also suggest that HSAD process at 25°C is comparatively efficient in saving heat energy and at the same time obtains the CH 4 values close to mesophilic conditions. This means that the smaller size digester (in the case of HSAD) is preferred as there is no waste dilution involved and also suitable for cold countries. Using this concept, livestock producers can play a role in reducing GHG emissions while also earning C-offset credits.
Two-phase anaerobic digestion of unscreened dairy manure
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Enhancement of Anaerobic digestion of cow manure through inoculation under mesophilic conditions
Now a days, anaerobic digestion (AD) systems are using a wide range of techniques to improve their performance, including co-digestion, inoculation, and addition of various accelerants. The AD of cow-manure (CM) was inoculated with ruminant intestinal waste (IW) in this study. It was hypothesized that methanogens present in intestinal waste will enhance anaerobic digestion, which will result in increased methane production. Five different CM/IW ratios (1:0, 9:1, 7:3, 1:1, 0:1) of wet weight were introduced in AD systems at mesophilic environmental (37 ◦C) to find the best combination of CM and IW. All of the mixture CM/IW ratios (9:1, 7:3, and 1:1) demonstrated a good synergistic effect and yielded a higher cumulative biogas yields than CM and RIW alone. The CM/IW (9:1) had the maximum cumulative biogas yield (239 mL/g VS), COD removal rate (40%), VS removal rate (27%), and total solid (TS) removal rate (24%). In the current study fertility status (nitrogen, N; phosphorus, P and pot...
The objective of this research is to compare dry anaerobic digestion of cow dung for methane production with wet anaerobic digestion under mesophilic and thermophilic temperatures in batch cultures for 63 days. The results showed that a specific methane yield of 0.333 and 0.345 LCH4/gVSr was obtained at 35 o C in the fermentation systems for a dilute ratio of 1:1 and 1:0, with a VS removal of 50.01%, and 56.33%, a COD removal of 54.99%, and 61.35%, respectively. When the fermentation systems was performed under 55 o C, the specific methane yield was increased to 0.351 and 0.374 LCH4/gVSr, with a VS removal of 53.43% and 60.52%, and a COD removal of 58.37% and 65.36%, respectively. Though addition of water could promote start-up process and biodegradability of the substrate to some extent, the methane yields in the dry anaerobic digestion process were found comparable to the conventional wet anaerobic digestion process. Furthermore, the volume of the reactor was increased twice in the wet fermentation process (7.68% TS) of cow dung compared to the dry fermentation (15.18% TS) at the same loading rate. It was suggested that dry methane fermentation process was superior in energy recovery, saving resources and engineering investment compared with wet fermentation process.
Thermophilic anaerobic co-digestion of separated solids from acidified dairy cow manure
Bioresource Technology, 2012
This study examined the potential for partly substituting dairy cow manure (DCM) with solids from solid to liquid separation of acidified dairy cow manure (SFDCM) during thermophilic anaerobic digestion. Three different substituting levels with a maximum of 30% substitution were tested. All digesters substituting DCM with SFDCM showed a stable biogas production with low volatile fatty acid concentrations after a short transition period. An increased methane yield in terms of digester volume compared to DCM alone was obtained with increasing amount of SFDCM and about 50% more methane was achieved when 30% of DCM was substituted with SFDCM. The digestates were subsequently digested in a post digestion, during which the methane yield increased proportionally with increasing amounts of SFDCM. It can be concluded that SFDCM is a suitable biomass for co-digestion and can be used to increase methane yield in terms of digester volume at ratios up to at least 30%.
Bioreactor Performance in the Anaerobic Digestion of Cattle Manure: A Review
A literature review has been undertaken to investigate the potential of anaerobic digestion for material recovery and energy production from cattle manure. These wastes constitute 8-20% total solid, with a volatile solid content of 70-85%. The biodegradable fractions include about 11% hemicellulose, 26-53% cellulose, and 11% lignin. Anaerobic digestion of cattle manure was studied under various operating conditions using different types of bioreactors and it allows the conversion of 50-75% of organic matter to methane with an organic loading rate of 1-6 g VS/L day. Continuous two-stage configuration involving a first-stage thermophilic reactor and mesophilic second reactor emerges to be superior and the most effective technologies for anaerobic digestion of cattle manure. It was demonstrated that 41% of volatile solids were converted to methane at an organic loading rate of 5.82 g VS/L day. The methane yield was found to be 620 L/kg VS added.
Enhancing the Performance of Anaerobic Digestion of Dairy Manure through Phase-Separation
Clean-soil Air Water, 2008
Anaerobic digestion (AD) is an effective way to convert animal manures into profitable by-products while simultaneously reducing the pollution of water, air, and soil caused by these wastes. Conventional high-rate anaerobic reactors cannot effectively process animal manures with high solids-containing wastes. The two-phase configuration for AD has several advantages over conventional one-phase processes, e. g., increased stability of the process, smaller size and cost efficient process configurations. In the present study, the experiments were carried out in a two-phase system composed of an acidogenic reactor and a methanogenic reactor, and in a one-phase system composed of only a methanogenic reactor. The reactors were operated as unmixed (without an external mixing aid), unsophisticated, and daily-fed mode. It was found that the two-phase configuration was more efficient than the one-phase system. The biogas production in the two-phase system at a hydraulic retention time (HRT) of 8.6 days (only methanogenic phase) was calculated to be 42% higher at an organic loading rate (OLR) of 3.5 g VS/L·day than that of the one-phase with a HRT of 20 days. This translates into significant performance improvement and reduced volume requirement. This finding represents a further step in the achievement of wider use of simple anaerobic reactor configurations for waste treatment in rural areas.