Anaerobic Digestion For Biogas Production Research Articles

Integrated approach to sustain biogas production in anaerobic digestion of chicken manure under recycled utilization of liquid digestate: Dynamics of ammonium accumulation and mitigation control

The dynamics of ammonium accumulation and mitigation control in anaerobic digestion of chicken manure under the recycled utilization of liquid digested slurry were investigated by using an integrated approach in two laboratory-scale semi-continuously stirred tank reactors. In the reactor with direct recycled utilization of the anaerobic digested liquid slurry, total volatilized fatty acids (in CH3COOH) and NH4+-N increased from 1600mg/L to 8000mg/L and from 2600mg/L to 5000mg/L, respectively. The daily volumetric biogas production decreased from 1.4±0.1L/(L·d) to 0.8±0.1L/(L·d) with a reduction efficiency of 43±4%. Air stripping was integrated for ammonium mitigation of recycled liquid digested slurry and was shown to effectively reduce the ammonium to 3000mg/L. Correspondingly, the biogas production was recovered back to 1.4±0.1L/(L·d). This indicated the potential of the integration of air stripping for ammonium mitigation in an anaerobic digestion process with liquid digested slurry recirculation.

Effects of biomass densification on anaerobic digestion for biogas production

To elucidate the possibility of applying biomass densification in anaerobic digestion, pelleting and briquetting were investigated for biogas production, and anaerobic digestion using densified biomass at higher solid content was also discussed.

The development, validation and initial results of an integrated model for determining the environmental sustainability of biogas production pathways

Biogas produced through Anaerobic Digestion can be seen as a flexible and storable energy carrier. However, the environmental sustainability and efficiency of biogas production is not fully understood. Within this article the use, operation, structure, validation, and results of a model for the environmental assessment of anaerobic biogas production pathways is discussed. The (Excel) BioGas Simulator or EBS model is capable of calculating the economic cost, efficiency, carbon footprint, and sustainability of small scale anaerobic digestion biogas production pathways (from 2000 up to 50000 ton/a biomass input). The results from the model are expressed in four main indicators: the economic cost in Net Present Value (NPV), the efficiency in Process Energy Returned On Invested or (P)EROI, the carbon footprint in Global Warming potential 100 year scale (GWP100), and the environmental impact in EcoPoints. The economic indicator is given in Euros in Net Present Value over a period of 25 years, the other indicators are given per Giga Joule of energy produced (e.g. kgCO2eq/GJ). The EBS model is based on a clear methodology, structured around the modular approach, energy and material flow analysis, and life cycle analysis. The modular approach separates the biogas production pathway into individual physical processes, which makes the model more transparent, flexible in use, and programmable with different settings. The aforementioned allows the research of several aspects of the biogas production pathway. Furthermore, the indication of sustainability in four clear indicators gives an understandable reference for comparison with other scenarios. Overall, the EBS model can help give insight on the sustainability of specific biogas production pathways and help indicate options for improvement. Results from the model indicate that from an energy efficiency and sustainability point of view, the anaerobic digestion process should be utilized for treating locally available waste feedstocks with the added advantage of producing energy, which should preferentially be used internally for powering the waste treatment process.

Investigation of thermal integration between biogas production and upgrading

Thermal integration of anaerobic digestion (AD) biogas production with amine-based chemical absorption biogas upgrading has been studied to improve the overall efficiency of the intergraded system. The thermal characteristics have been investigated for industrial AD raw biogas production and amine-based chemical absorption biogas upgrading. The investigation provides a basic understanding for the possibilities of energy saving through thermal integration. The thermal integration is carried out through well-defined cases based on the thermal characteristics of the biogas production and the biogas upgrading. The following factors are taken into account in the case study: thermal conditions of sub-systems, material and energy balances, cost issues and main benefits. The potential of heat recovery has been evaluated to utilise the waste heat from amine-based upgrading process for the use in the AD biogas production. The results show that the thermal integration has positive effects on improving the overall energy efficiency of the integrated biogas plant. Cost analysis shows that the thermal integration is economically feasible.

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

Floating tests were conducted in anaerobic digestion with different OLR of corn stover to investigate formation of floating layers and to find proper agitation interval for preventing floating layer formation. Floating layers were formed in the early stage of no-agitation period. The daily biogas production was decreased by 81.87–87.90% in digesters with no agitation and feeding compared with digesters having agitation. Reduction of biogas production was mainly attributed to poor contact of substrate-microorganisms. Agitation intervals of 10h, 6h, and 2h were found to be proper for eliminating floating layer at OLR of 1.44, 1.78 and 2.11g(TS)L−1d−1, respectively. The proper agitation interval was further validated by anaerobic experiments. It showed that proper agitation interval could not only prevent floating layer formation and achieve high biogas production but also increase energy efficiency of anaerobic digestion. The finding is useful for operating anaerobic digester with corn stover in a cost-effective way.

Response of a continuous biomethanation process to transient organic shock loads under controlled and uncontrolled pH conditions

The organic loading rate (OLR) is a critical factor that controls the treatment efficiency and biogas production in anaerobic digestion (AD). Therefore, organic shock loads may cause significant process imbalances accompanied by a drop in pH and acid accumulation or even failure. This study investigated the response of a continuous mesophilic anaerobic bioreactor to a series of transient organic shock loads of the substrate whey permeate, a high-strength organic wastewater from cheese making. The reactor was subjected to organic shock loads of increasing magnitude (a one-day pulse of elevated feed organic concentration) under controlled (near 7) and uncontrolled pH conditions at a fixed HRT of 10 days. The reactor was resilient to up to a shock load of up to 8.0 g SCOD/L·d under controlled pH conditions but failed to recover from the serious imbalance caused by a 3.0-g SCOD/L·d shock load, thus indicating the critical effect of pH on system resilience. The acidified reactor was not restored by interrupted feeding under the acidic conditions that were formed (pH ≤ 4.5) but was successfully restored after pH adjustment to 7. The reactor subsequently reverted to continuous mode without pH control and showed a performance comparable to the stable performance at the design OLR of 1.0 g SCOD/L·d. The bacterial community structure shifted dynamically in association with disturbances in the reactor conditions, whereas the archaeal community structure remained simple and less variable during the shock loading experiments. The structural shifts of the bacterial community were well correlated with the process performance changes, and performance recovery was generally accompanied by recovery of the bacterial community structure. The overall results suggest that the reactor pH, rather than simply acting as an accumulation of organic acids, had a crucial effect on the resilience and robustness of the microbial community and thus on the reactor performance under organic shock loads.

Semi-continuous anaerobic digestion for biogas production: influence of ammonium acetate supplement and structure of the microbial community.

BackgroundAs an efficient disposal method of food waste, anaerobic digestion (AD) for biogas production is widely used. In order to understand the enhanced efficiency and stability of AD by appropriate amounts of ammonia and volatile fatty acids (NH4+/VFAs), the characteristics of the corresponding microbial community with ammonium acetate supplement were investigated by denatured gradient gel electrophoresis (DGGE) and pyrosequencing analyses of samples, with or without supplement of NH4+/VFAs.ResultsIn this study, four different supplement strategies of adding ammonium acetate were investigated, including a blank group (without supplement of ammonium acetate), a low group (L group, 0.7 g/L/d), a moderate group (M group, 1.0 g/L/d) and a high group (H group, 1.3 g/L/d), respectively. The average daily gas production was 1,839 mL/d, 1,655 mL/d, 1,448 mL/d and 1,488 mL/d for L, M, H and blank groups, respectively. The results reveal that the absence or overload of NH4+/VFAs leads to the inhibition or failure of the AD operation. The blank and H groups were selected for further investigation of the microbial community by DGGE and pyrosequencing analyses. A significant difference of the microbial communities at different AD stages was observed between the blank and H groups.ConclusionsAmmonium acetate, as an efficient supplement, significantly influences the characteristics of a semi-continuous AD operation. The DGGE and pyrosequencing analyses indicated that the different bacterial and archaeal communities occurred in the blank and H groups at different AD stages. Thus, an appropriate ammonium acetate supplement may maintain the balance of the microbial community and could be applied to adjust the AD operation and microbial composition towards optimal biogas production.

Coupling electric energy and biogas production in anaerobic digesters – impacts on the microbiome

Microbiome based anaerobic digestion combined with microbial electrochemical technologies exploits biomass efficiently and flexibly by concurrent conversion to methane and electrons.

Humic Acid-Like and Fulvic Acid-Like Inhibition on the Hydrolysis of Cellulose and Tributyrin

Enzymatic hydrolysis of complex wastes is a critical step for efficient biogas production in anaerobic digesters. Inhibition of this hydrolytic step was studied by addition of humic acid-like (HAL) and fulvic acid-like (FAL) substances, extracted from maize silage and fresh cow manure, to batch tests with cellulose and cellulases from Aspergillus niger and tributyrin and lipases from Candida rugosa. To confirm the inhibition results, microbially catalysed hydrolysis trials were performed, where Fibrobacter succinogenes was grown exclusively on cellulose. Hydrolysis products, as glucose, glycerol and butyric acid, were measured to determine the hydrolysis efficiency and its rate. Cellulose hydrolysis was inhibited by 0.5 to 5.0 g l−1 of HAL and FAL substances extracted from maize and cow manure, which are relevant concentrations for manure and maize digestion. Tributyrin hydrolysis, on the other hand, was only inhibited by 0.5 to 5.0 g l−1 of HAL substances extracted from maize and cow manure and not by FAL substances.

Kinetics of biological decolorisation of anthraquinone based Reactive Blue 19 using an isolated strain of Enterobacter sp.F NCIM 5545

In the present study, an attempt was made to evaluate the bacterial decolorisation of Reactive Blue 19 by an Enterobacter sp.F which was isolated from a mixed culture from anaerobic digester for biogas production. Phenotypic characterization and phylogenetic analysis based on DNA sequencing comparisons indicate that Enterobacter sp.F was 99.7% similar to Enterobacter cloacae ATCC13047. The kinetics of Reactive Blue 19 dye decolorisation by bacterium had been estimated. Effects of substrate concentration, oxygen, temperature, pH, glucose and glucose to microbe weight ratio on the rate of decolorisation were investigated to understand key factor that determines the performance of dye decolorisation. The maximum decolorisation efficiency of Reactive Blue 19 was 90% over period of 24h for optimized parameter.To the best of our knowledge, this research study is the report where Enterobacter sp.F has been reported with about 90% decolorizing ability against anthraquinone based Reactive Blue 19 dye.

Climate impact and energy efficiency from electricity generation through anaerobic digestion or direct combustion of short rotation coppice willow

Short rotation coppice willow is an energy crop used in Sweden to produce electricity and heat in combined heat and power plants. Recent laboratory-scale experiments have shown that SRC willow can also be used for biogas production in anaerobic digestion processes.Here, life cycle assessment is used to compare the climate impact and energy efficiency of electricity and heat generated by these measures. All energy inputs and greenhouse gas emissions, including soil organic carbon fluxes were included in the life cycle assessment. The climate impact was determined using time-dependent life cycle assessment methodology.Both systems showed a positive net energy balance, but the direct combustion system delivered ninefold more energy than the biogas system. Both systems had a cooling effect on the global mean surface temperature change. The cooling impact per hectare from the biogas system was ninefold higher due to the carbon returned to soil with the digestate.Compensating the lower energy production of the biogas system with external energy sources had a large impact on the result, effectively determining whether the biogas scenario had a net warming or cooling contribution to the global mean temperature change per kWh of electricity. In all cases, the contribution to global warming was lowered by the inclusion of willow in the energy system. The use of time-dependent climate impact methodology shows that extended use of short rotation coppice willow can contribute to counteract global warming.

Urea (CO(NH<sub>2</sub>)<sub>2</sub>) Pretreatment Improve Biogas Production Performance of Rice Straw

To discuss the internal effect of urea (CO(NH2)2) pretreatment on anaerobic digestion biogas production of rice straw waste, a self-designed laboratory-scale continuous anaerobic biogas digester was used in this study. Anaerobic biogas slurry, urea pretreatment and anaerobic digestion were evaluated for biogas production from rice straw. The results showed that the peak value of biogas production was attained on the 17th day by using 6% urea pretreatment on rice straw. However, the highest CH4 content was 49.8% on the 15th day for the 8% urea-treated rice straw. The cumulative biogas production of 6% urea pretreatment was the highest, about 16 540 mL, which was followed by 2% urea (12 283 mL), 8% urea (9 883 mL), and 4% urea (5 668 mL).

English

Bioconversion of dog waste (dung) to energy as one of the ways for proper disposal of the waste was carried out through anaerobic digestion for biogas production. The 59-day experiment was performed within the slurry temperature range of 28 and 44°C using a 50 L metallic biodigester. Prior to charging the digesters, physico-chemical properties and microbial content of the waste were determined using standard methods. The results show that a cumulative gas production of 200 L was generated by 7 kg of the waste at the end of the test period while the microbial load decreased from 8.2×1014 at the beginning of the test to 4.2×108 at the end of the retention time. Five microorganisms were identified at the beginning of the charging period, four were identified at the 20th day when the gas began to burn due to methane production while only one microorganism was identified at end of the test.  Even though it has longer retention period than most common animal wastes used for biogas production, its gas production rate is low. However, pathogen reduction through anaerobic digestion justifies its conversion to energy by this method.   Key words: Dog Waste, biogas, anaerobic digestion, renewable energy, biodigesters, microbial count.

Decentralized Biogas Technology of Anaerobic Digestion and Farm Ecosystem: Opportunities and Challenges

Long-term economic and environmental concerns have resulted in a great amount of research on renewable sources of biomass and bioenergy to replace fossil fuels in the past decades. Decentralized biogas technology is one of the most potential technologies of biomass and bioenergy by using agricultural waste materials (e.g., animal manure, crop straw and by-products from food industries) as feedstocks. By-products from biogas production, called digestate, are nutrient rich which could potentially be reused as green fertilizers in agriculture, thereby providing a sustainable substitute for synthetic fertilizers for ecosystem farm. Thus, the biogas production of anaerobic digestion (AD) is win-win option for livestock and crop producers to address issues of waste management and energy supply, and to avoid contamination of surface and ground waters and emissions of odors and greenhouse gases. In this paper, we review biogas production technology and then evaluate environmental effects of digestate used as fertilizer. Finally, we discuss issues of deployment of decentralized biogas technology for ecosystem farms. Economic and technological barriers still exist for large scale deployment of biogas technology. Two national scale deployments in China and Nepal showed that the operational status of biogas digesters is not optimal and up to 50% of plants are non-functional after a short operation period regardless of the social and economic factors. Main barriers are a wide variation of feedstocks and environmental conditions (e.g., temperature) over space and time. It becomes clear that the experimental conditions of the pilot plants need to be adjusted and calibrated to the local feedstocks and climate. Also, more research needs to be done in cold fermentation technology.

A novel process simulation model (PSM) for anaerobic digestion using Aspen Plus

A novel process simulation model (PSM) was developed for biogas production in anaerobic digesters using Aspen Plus®. The PSM is a library model of anaerobic digestion, which predicts the biogas production from any substrate at any given process condition. A total of 46 reactions were used in the model, which include inhibitions, rate-kinetics, pH, ammonia, volume, loading rate, and retention time. The hydrolysis reactions were based on the extent of the reaction, while the acidogenic, acetogenic, and methanogenic reactions were based on the kinetics. The PSM was validated against a variety of lab and industrial data on anaerobic digestion. The P-value after statistical analysis was found to be 0.701, which showed that there was no significant difference between discrete validations and processing conditions. The sensitivity analysis for a ±10% change in composition of substrate and extent of reaction results in 5.285% higher value than the experimental value. The model is available at http://hdl.handle.net/2320/12358 (Rajendran et al., 2013b).

Performances of Leaching-UBF Anaerobic Digestion for Biogas Production of Kitchen Waste

The performances of leaching-upflow blanket filter (UBF) anaerobic digestion for biogas production of kitchen waste was investigated. To find out the process parameter variations of acidification phase and the methane production performance of methanogenic phase, kitchen waste from division of environment sanitation management of Changzhou was used as feedstock. The results show that the ammonia in anaerobic system cumulated continuously throughout the digestion; pH value maintained at7.6; At first the value of COD ranged from 20000 mg/L to 140000 mg/L to the final UBF water 10000mg/L to 12000 mg/L; Volatile fatty acid (VFA) reduced to 150mg/L with the increase of the days; total nitrogen increases first and then decreases, finally, it keeps at 1600 mg/L; The concentration of alkalinity increased slightly; biogas production is stable, The rate of gas generation is above0.30 m3/kgCOD . These results provide a proof of the feasibility for kitchen waste anaerobic methane fermentation.

Long-term anaerobic digestion of microalgae grown in HRAP for wastewater treatment. Effect of microwave pretreatment

This paper describes the anaerobic digestion of microalgal biomass from high rate ponds in continuous anaerobic reactors for biogas production. With hydraulic retention times (HRT) of 15 and 20 days, the volatile solids (VS) removal did not exceed 30%, and the methane production rate ranged between 0.12 and 0.14 L CH4/L day. To improve process performance, microwave irradiation at 900 W for 3 min (specific energy ∼70,000 kJ/kg VS) was applied as a pretreatment step. The VS removal increased to 40 and 45% at 15 and 20 days HRT, respectively. Consequently, the methane production rate increased to 0.16 and 0.20 L CH4/L day at 15 and 20 days HRT, respectively. Microscopic analysis confirmed cell wall damage, although generally without lysis, after irradiating microalgal biomass. However, the energy consumption was much higher than the extra energy production of the process. Indeed, microalgal biomass should not only be thickened but also dewatered if microwave irradiation was to be applied as a pretreatment to anaerobic digestion for biogas production.

Preliminary experimental results of Sewage Sludge (SS) Co-digestion with Palm Oil Mill Effluent (POME) for Enhanced Biogas Production in Laboratory Scale Anaerobic Digester

An investigation on the feasibility of co-digesting Sewage Sludge with Palm Oil Mill Effluent for enhancing the biogas production and the corresponding effect of the co-digestion substrate ratio on the biogas production has been evaluated. Anaerobic co-digestion of POME with SS was performed at ratios of 100:0, 70:30, 60:40 and 0:100 to find the optimum blend required for enhanced waste digestion and biogas production. Single stage batch digestion was carried out for 12 days in a laboratory scale anaerobic digester. Co-digestion of sludge's at the 70:30 proportion resulted in optimal COD and C: N ratio which subsequently recorded the highest performance with regards to biogas production at 28.1 L's compared to the 1.98 L's of biogas produced from digestion of SS alone. From the results obtained, it is evident that co-digestion of POME and SS is an attractive option to be explored for enhancement of biogas production in anaerobic digesters.

Environmental Advances Due to the Integration of Food Industries and Anaerobic Digestion for Biogas Production: Perspectives of the Italian Milk and Dairy Product Sector

Anaerobic digestion (AD) is a biotechnology that is able to produce an energy vector from waste organic materials. Its inclusion in the food industries, especially if farming activities are present, represents an interesting perspective. This work reviews the main aspects of the inclusion of AD in milk and dairy production. It includes an analysis of the sector characteristics in terms of diffusion, a discussion of waste production and disposal concerning milk and dairy production, a description of the biological and technological aspects of AD, a discussion regarding the application of AD for milk by-products, a description of environmental and legislative aspects, and the suggestion of an integrated model that includes the anaerobic co-digestion of whey and cattle slurry in the milk and dairy production industries. Both environmental and economic impacts of such integration promise to pay for the preliminary investment in AD plant installation and the development of additional expertise.

Anaerobic digestion of activated sludge after pressure-assisted ozonation

This study was undertaken to examine the benefits of pressure-assisted ozonation (PAO) in enhancing solids reduction and biogas production in anaerobic digestion. The results showed significant improvements in both. With unacclimated inoculum at varied food-to-inoculum (F/I) ratios of 0.5-2, solids and COD reductions were improved by PAO, as well as by increased F/I ratios even without PAO, which would warrant further optimization of the F/I ratio for an unacclimated inoculum. With acclimated inocula at F/I ratio of 0.8, volatile suspended solids reduction and biogas production were improved by up to 60% and 800%, respectively, when the AS had been subjected to 20 cycles of PAO. In extended operation in plants where acclimated anaerobes are encountered, PAO pretreatment offers improved digestion of AS in terms of solids and COD removals and biogas production.