Anaerobic Digestion Of Animal Waste Research Articles

Livestock waste management for energy recovery in Brazil: a life cycle assessment approach.

Livestock farming has exerted intense environmental pressure on our planet. The high emissions to the environment and the high demands of resources for the production process have encouraged the search for decarbonization and circularity in the livestock sector. In this context, the objective of this study was to evaluate and compare the environmental performance of two different uses for biogas generated in the anaerobic digestion of animal waste, either for electricity generation or biomethane. For this purpose, a life cycle assessment approach was applied to evaluate the potential of anaerobic digestion as a management technology for three different livestock wastes, related to beef cattle, dairy, and sheep in the Brazilian animal production context. The results suggest that the treatment scenarios focusing on biomethane generation were able to mitigate the highest percentage of damages (77 to 108%) in the global warming category when compared to the scenarios without the use of anaerobic digestion (3.00·102 to 3.71·103 kgCO2 eq) or in the perspective of electricity generation (mitigation of 74 to 96%). In terms of freshwater eutrophication, the generation of electricity (- 2.17·10-2 to 2.31·10-3 kg P eq) is more favorable than the purification of biogas to biomethane (- 1.73·10-2 to 2.44·10-3 kg P eq), due to the loss of methane in the upgrading process. In terms of terrestrial ecotoxicity, all scenarios are very similar, with negative values (- 1.19·101 to - 7.17·102 kg 1,4-DCB) due to the benefit of nutrient recovery, especially nitrogen, associated with the use of digestate as fertilizer, which was one of the critical points in all scenarios. Based on these results, it is evident that proper management of all stages of the treatment life cycle is the key to decarbonization and circularity in livestock waste management. The biogas use does not present different effects on the environmental performance of the scenarios studied, demonstrating that the purpose should be chosen according to the needs of each plant or management system.

Modelling and Optimization of Methane from Anaerobic Digestion of Animal Waste (Pig Dung) with Adaptive Neuro Fuzzy Inference System (ANFIS)

Agricultural wastes have increased in recent times due to an increased need for agricultural products by humans. These wastes causes environmental pollution and hazard to the society. Hence, the need to embark on anaerobic digestion to convert these waste to biogas. Biogas has been proven to be a good alternative to gases produced from fossil fuel due to its environmental friendliness. Production of biogas gases ensures cleaner environment and enhances clean growth. In this study, hydraulic retention time, temperature, moisture content, pH and carbon to nitrogen ratio are the factors used for generating the biogas from anaerobic digestion of pig dung. Independent variables range values obtained for each factor was subjected to design expert software application which gave the factor levels and number of runs under Central Composite Design (CCD) in Design of Experiment (DOE). The data generated from design expert was utilized in the laboratory for biogas yield via bio-digester. Pig dung was made to meet various process conditions after which 2kg of pig dung was feed into a 10liters digester and kept for various days. The yield obtained was subjected to four RSM models (linear model, interaction model, pure-quadratic model and quadratic model), ANFIS model and three kinetic models (gompert, modified gompertz and logistic model). Quadratic model was selected as the best RSM model having the best prediction accuracy performance with R-square value of 73.03%. When compared with ANFIS model, ANFIS model had R-square of 95.9983% there by making it a better model which can be utilized for further analysis. ANFIS was optimized and a three dimensional plot of surface and contour plot were used to determine the effect of the factors on the interaction and the optimal response obtained was 92.36% at hydraulic retention time of 11days, temperature of 50oC, moisture content of 93%, pH value of 7.01 and carbon to nitrogen ratio of 1 which was used as the first guess for kinetic studies. Furthermore, logistic model had the best prediction accuracy with R-square of 68.09% when compared with the other two kinetic models, hence, it was concluded that ANFIS model should be utilized in determination of the yield using the factors and logistic model, this could be used in the study of the anaerobic bio-digesters for the production of biogas from pig dung.

The challenges and perspectives for anaerobic digestion of animal waste and fertilizer application of the digestate

The increase in livestock production creates a serious problem of managing animal waste and by-products. Among the wide range of waste valorization methods available, anaerobic digestion is very promising. It is a form of material recycling that also produces renewable energy in the form of biogas, which is reminiscent of energy recycling. The effluent and digestate from the anaerobic digestion process need to be processed further. These materials are widely used in agriculture due to their composition. Both the liquid and solid fractions of digestate are high in nitrogen, making them a valuable source for plants. Before soil or foliar application, conditioning (e.g., with inorganic acids) and neutralization (e.g., with potassium hydroxide) is required to eliminate odorous compounds and microorganisms. Various methods of conducting the process by anaerobic digestion (use of additives increasing activity of microorganisms, co-digestion, multiple techniques of substrate preparation) and the possibility of controlling process parameters such as optimal C/N ratio (15–30), optimal temperature (psychrophilic (<20 °C), mesophilic (35–37 °C) and thermophilic (55 °C) for microorganism activity ensure high efficiency of the process. Literature data describing tests of various digestates on different plants prove high efficiency, determined by yield increase (even by 28%), nitrogen uptake (by 20%) or phosphorus recovery rate (by 43%) or increase of biometric parameters (e.g., leaf area).

Evaluation and optimization of electricity generation through manure obtained from animal production chains in two Brazilian mesoregions

Biogas, obtained from the anaerobic digestion of animal waste, is being increasingly used worldwide, and is generating significant economic and environmental benefits. It is ideal for regions that are mainly involved in agricultural activities and animal husbandry. Thus, the objective of this study was to estimate the energy potential and to optimize the allocation of electric power generation plants that use biogas in the mesoregions of Minas Gerais, Brazil, based on the distribution generation standards and availability of resources. To calculate the energy potential, data from governmental platforms were used, referring to the number of animals in the study regions as well as theoretical conversion models in the literature. To optimize the allocation of biogas plants, QGis software and a constructive algorithm that was developed for this study were used to build maps that demonstrated the optimal allocation of these plants, based on their potential and geographical location. To convert biomethane into electricity using a combustion engine (28% efficiency), energy potentials of 791.8 and 218.3 GWh yr−1 and 21 and 6 plants located in Zona da Mata and Campo das Vertentes, respectively, were estimated. With respect to the combine cycle (65% efficiency), energy potentials of 1838.2 and 506.7 GWh yr−1 and 47 and 14 plants in Zona da Mata and Campo das Vertentes, respectively, were estimated. New plants were calculated to increase the energy generation in the evaluated regions by 8–19%. The average cost of energy generation using stationary engine and combined cycle were USD 0.2384 kWh−1 and USD 0.0974 kWh−1, respectively. A reduction in CO2 emissions per inhabitant is expected for the assessed region, ranging between 6.05% and 14.52%. A significant portion of the state's rural electricity consumption could be supported by these new ventures, leading to an increase in energy security as well as reliability in meeting demand. In addition, the developed optimization algorithm can be used as a decision-making tool to determine locations for the construction of biogas plants in other regions of Brazil.

The Effect of Biogas Slurry Application on Biomass Production and Forage Quality of Lolium Multiflorum

The development of ecological circular agriculture has been highly encouraged to recycle agricultural wastes, reduce mineral fertilizer input, and protect the environment. Biogas slurry (BS), a by-product of biogas production generated from anaerobic digestion of animal waste and crop residues, is often considered a substitute to reduce mineral fertilizer input. Being a cheap source of organic matter and plant nutrients, its application may improve soil fertility and yield quality and quantity. The field experiments were conducted in 2016 and 2017 to study the plant growth responses and forage quality by applying biogas slurry to replace chemical synthetic fertilizer (CSF). Results revealed that biogas slurry combination with chemical synthetic fertilizer significantly (p &lt; 0.05) improved the growth of Italian ryegrass on treatment with T2, and the Italian ryegrass dry matter was increased by more than 9.00%, while the stem-to-leaf ratio was decreased by more than 12% (second cutting), in comparison with only chemical synthetic fertilizer group. In the case of forage quality, the crude protein (CP) and crude fiber (CF) content had a significant difference was observed between the T0 and T2 treatment group. Compare with the chemical synthetic fertilizer group, the CP content improved by 10.35%, and the CF content decreased about 10.00%. Based on these results, it was concluded that the application of 37.5 kg/ha CSF + 100.5 t/ha BS could improve the production of biomass and forage quality in Italian ryegrass.

Animal waste utilization technology

The applicability of learned introduction of anaerobic digestion of animal waste will be obvious after a wide setting of afull-scale experiment and an across-the-board economic feasibility.However, yet today, basing on the domestic and abroad practice on biopowerdigesters engineering and operation,it can be argued that their use is economically advantageous than the traditional system. The obtained experience evidences thatthe cubicle housingof dairy cows is advanced. Milking operation is carried out in a special house, which ramps up milkquality, improves working conditions for milkmaids, and reduces labor costs.The problem of the animal waste impact on environment, especially on natural waters is acute. There is no summarized information about their distribution for fertilization and discharge.Not only liquid animal waste, but also silage sap causepollution. The Energy Program sets the task of widespread involvement of non-conventional energyin the country's energy balance. Biomass is of the great importance among such sources in the agro-industrial complex of the country.Anaerobicmethanoic digestion of animal waste allows evolving biogas – a valuable organic fertilizer with extra biological activityor protein-vitamin concentrates for feed supplementation.Such digestion of animal waste is an effective environmental action that provides its deodorization, reduction of soil and water pollution with repugnant substances and pathogenic microflora, atmospheric emissions (due to removal)

Application of Biogas Slurry in Combination with Chemical Fertilizer Enhances Grain Yield and Profitability of Maize (Zea Mays L.)

ABSTRACT Biogas slurry is a by-product of biogas production, which is generated from anaerobic digestion of animal waste and crop residue. It is generally considered a waste material. However, its application can improve soil health, crop yield, and profitability of the farmers as it is a rich source of organic matter and plant nutrients. Field experiments were conducted to evaluate the combined effect of biogas slurry and chemical fertilizer on grain yield of maize and economic return. The treatments were soil test-based chemical fertilizer, chemical fertilizer + cow dung manure (5 t h–1) or poultry manure (3 t h–1), chemical fertilizer + cow dung biogas slurry (5 t h–1) or poultry biogas slurry (3 t h–1) along with traditional farmer practice as the control. Application of biogas slurry from cow dung or poultry manure in combination with chemical fertilizer resulted in 20–24% higher grain yield along with 22–23% greater gross return and 52–53% more gross margin compared with the traditional farmer practice indicating the beneficial effect of integrated application of biogas slurry and chemical fertilizer on maize productivity and financial return. Integrated application of biogas slurry and chemical fertilizer has a good potential in maize production as it provides higher grain yield and economic profitability.

Abundances of Tetracycline Resistance Genes and Tetracycline Antibiotics during Anaerobic Digestion of Swine Waste.

The impact of anaerobic digestion of animal waste on the persistence of antibiotic resistance genes (ARGs) and antibiotics is not widely studied. Two identical, 800-L digesters seeded with swine slurry were followed up to 100 d in three separate trials. The trials received varying amounts of antibiotic-free corn ( L.) mixed with water to maintain the digestion process. Biogas production, seven tetracycline resistance () genes, and three tetracyclines and their transformation products were measured. Biogas production proportionally increased as the feeding loads increased between trials. In Trial 1, log gene copies showed small but statistically significant ( < 0.01) increases during digestion. In Trial 2, anaerobic digestion did not have a significant ( > 0.05) effect except for significant reductions in B ( < 0.0001) and G ( = 0.0335) log gene copies. In Trial 3, which received the highest amount of corn mix, log copies of the 16S ribosomal RNA and the genes significantly ( < 0.0001) reduced over time during digestion. Up to 36 μg L tetracycline, 112 μg L chlortetracycline, 11.9 mg L isochlortetracycline, and 30 μg L 4-epitetracycline were detected both in the liquid and solid digestates. Results of this study revealed that although anaerobic digestion of swine waste can produce useful biogas, it does not result in complete removal of bacteria, ARGs, and antibiotics regardless of differences in the feeding loads between trials. Further effluent and sludge treatments are required prior to their downstream use in crop production to minimize emergence and environmental dissemination of antimicrobial-resistant bacteria through animal manure.

Influence of cefazolin contamination on performance of two-stage and single stage anaerobic batch digesters

Anaerobic digestion of animal waste is a well-established technology for on-farm waste management and energy generation. Animal wastes often contain toxic substances such as antibiotic, which have been shown to cause varying degrees of biogas inhibition in single stage (SS) digestion system. Currently, useful information on influence of antibiotic contamination of substrates, particularly cefazolin (CFZ), on two-stage (TS) digestion system is limited. The effect of CFZ antibiotic on performance of two-stage and single batch systems digesting mixture of manure and milk from dairy cow was investigated. Batch experiments were conducted at 55 °C in TS (5 and 15 days for first and second stages, respectively) and SS (20 days) digesters. Cefazolin was added at concentration of 5, 10, 20, 40 and 80 mg/l. Control experiments, with no addition of CFZ were also conducted. In TS system, all concentrations of CFZ exhibited complete or near complete inhibition of hydrogen production in the first stage, with methane reductions of 9.2–56.0% in the second stage as compared with control treatment. Corresponding biogas inhibitions for the system ranged from 7.3–29.1%. The inhibition resulted in reduction of energy recovery by 16.7–60.6%. For SS system, CFZ addition reduced 39.8–68.3% of methane production while total biogas inhibition ranged 24.0–39.0%. The inhibition also resulted in reduction of energy recovery by 39.7–68.3%. Evidently, lower biogas inhibitions and reduction in energy recovery were experienced in TS system as compared with SS system. The results thus suggest that TS system can be an alternative to conventional SS system for on-farm management of CFZ contaminated wastes.

Yield and Profitability of Tomato as Influenced by Integrated Application of Synthetic Fertilizer and Biogas Slurry

ABSTRACTBiogas slurry, a by-product of biogas production generated from anaerobic digestion of animal waste and crop residues, is often considered a waste product. Being a cheap source of organic matter and plant nutrients, its application may improve soil fertility, and yield quality and quantity. Field experiments were conducted at Lahirirhat Farming System Research and Development site, Rangpur, Bangladesh, to assess effects of biogas slurry in combination with synthetic fertilizer on tomato (Solanum lycopersicum L.) yield and profitability. Treatments included: soil test-based fertilizer, synthetic fertilizer+cow dung manure @ 5 t∙ha−1, synthetic fertilizer+cow dung bioslurry @ 5 t∙ha−1, synthetic fertilizer+poultry manure @ 3 t∙ha−1, synthetic fertilizer+poultry bioslurry @ 3 t∙ha−1, and farmer practice. Fruit yield was higher for plants grown with synthetic fertilizer+cow dung bioslurry compared with other fertilizer treatments and the farmer practice. Application of synthetic fertilizer+poultry bioslurry resulted in the highest fruit yield; plants maintained with the farmer practice yielded the least. The highest gross return and gross margin were obtained from plants treated with synthetic fertilizer+cow dung bioslurry. Synthetic fertilizer+poultry bioslurry-treated plants returned the highest gross return and gross margin. Application of synthetic fertilizer in combination with bioslurry has potential in increasing tomato yield and economic return of farmers.

Preliminary study of biogas production from agricultural waste in friuli Venezia Giulia (nord-east of Italy)

The latest directives of the Energy and Environment Policy of the European Union (EU) established a new framework for renewable sources (Directive EC 28/2009; European Commission, 2009). The Italian Energy Action Plan of 2010 set a target of at least 17% of total energy generated from renewable sources by 2020. In this context biogas from waste and biomass is a potential energy source that can be used for the production of heat, electricity and fuel. The objective of this work was to determine the potential energy production from anaerobic digestion of animal wastes and agricultural residues in Friuli Venezia Giulia (Nord-East Italy).

Development perspectives for biogas production from agricultural waste in Friuli Venezia Giulia (Nord-East of Italy)

The latest directives of the Energy and Environment Policy of the European Union (EU) established a new framework for renewable sources (Directive EC 28/2009; European Commission, 2009). The Italian Energy Action Plan of 2010 set a target of at least 17% of total energy generated from renewable sources by 2020. In this context biogas from waste and biomass is a potential energy source that can be used for the production of heat, electricity and fuel. The objective of this work was to determine the potential energy production from anaerobic digestion of animal wastes and agricultural residues in Friuli Venezia Giulia (Nord-East Italy). For an assessment of biogas as an energy source, based on direct conversion by agricultural farms, it is important to establish the amount of the waste. In this study, biogas amount which can be obtained was calculated for all municipalities in the Friuli Venezia Giulia Region (North-East of Italy) by using the number of livestock animals, the cereal area for agricultural residues and also considering various criteria such as the rate of dry matter and availability. The calculated regional biogas potential is about 187 (N)Gm3 when using animal waste, straw and corn stalk. The potential of biogas energy equivalent of Friuli Venezia Giulia is about 3 600 TJ (LHV) may be able to replace 2.6% of final energy consumption in Friuli Venezia Giulia (3 339 ktoe) and about 10% of the final electricity consumption (864 ktoe) considering an electrical efficiency of 30% with the biogas engine.

Development perspectives for biogas production from agricultural waste in Friuli Venezia Giulia (Nord-East of Italy)

The latest directives of the Energy and Environment Policy of the European Union (EU) established a new framework for renewable sources (Directive EC 28/2009; European Commission, 2009). The Italian Energy Action Plan of 2010 set a target of at least 17% of total energy generated from renewable sources by 2020. In this context biogas from waste and biomass is a potential energy source that can be used for the production of heat, electricity and fuel. The objective of this work was to determine the potential energy production from anaerobic digestion of animal wastes and agricultural residues in Friuli Venezia Giulia (Nord-East Italy). For an assessment of biogas as an energy source, based on direct conversion by agricultural farms, it is important to establish the amount of the waste. In this study, biogas amount which can be obtained was calculated for all municipalities in the Friuli Venezia Giulia Region (North-East of Italy) by using the number of livestock animals, the cereal area for agricultural residues and also considering various criteria such as the rate of dry matter and availability. The calculated regional biogas potential is about 187 (N)Gm3 when using animal waste, straw and corn stalk. The potential of biogas energy equivalent of Friuli Venezia Giulia is about 3 600 TJ (LHV) may be able to replace 2.6% of final energy consumption in Friuli Venezia Giulia (3 339 ktoe) and about 10% of the final electricity consumption (864 ktoe) considering an electrical efficiency of 30% with the biogas engine.

Kinetics evaluation of a semi-continuously fed anaerobic digester treating pig manure at two mesophilic temperatures

Anaerobic digestion of animal waste at a low range of mesophilic conditions has not been well described to date. In this study, laboratory-scale semi-continuously fed anaerobic digesters treating pig manure were operated at 28 and 38 °C with organic loading rates ranging from 1.3 to 4.3 g ODM L−1 d−1. The estimated biomass yield was higher at 28 °C (0.065 g VSS g−1 CODremoved) than at 38 °C (0.016 g VSS g−1 CODremoved). The resulting calculated biomass concentration range at 28 and 38 °C was 1.2–2.4 and 0.3–0.6g VSS L−1, respectively, which fitted well with a Michaelis–Menten type function. These VSS results are one or two orders of magnitude lower than previously reported for manure-fed digesters. Although maximum specific substrate utilisation rate at 38 °C is five-fold that at 28 °C, higher biomass yield in the digester at 28 °C seemed to compensate for the adverse effects of lower temperature on digester performance.

Development perspectives for biogas production from agricultural waste in Friuli Venezia Giulia (Nord-East of Italy)

The latest directives of the Energy and Environment Policy of the European Union (EU) established a new framework for renewable sources (Directive EC 28/2009; European Commission, 2009). The Italian Energy Action Plan of 2010 set a target of at least 17% of total energy generated from renewable sources by 2020. In this context biogas from waste and biomass is a potential energy source that can be used for the production of heat, electricity and fuel. The objective of this work was to determine the potential energy production from anaerobic digestion of animal wastes and agricultural residues in Friuli Venezia Giulia (Nord-East Italy). For an assessment of biogas as an energy source, based on direct conversion by agricultural farms, it is important to establish the amount of the waste. In this study, biogas amount which can be obtained was calculated for all municipalities in the Friuli Venezia Giulia Region (North-East of Italy) by using the number of livestock animals, the cereal area for agricultural residues and also considering various criteria such as the rate of dry matter and availability. The calculated regional biogas potential is about 187 (N)Gm3 when using animal waste, straw and corn stalk. The potential of biogas energy equivalent of Friuli Venezia Giulia is about 3 600 TJ (LHV) may be able to replace 2.6% of final energy consumption in Friuli Venezia Giulia (3 339 ktoe) and about 10% of the final electricity consumption (864 ktoe) considering an electrical efficiency of 30% with the biogas engine.

Life-cycle energy use and greenhouse gas emissions of production of bioethanol from sorghum in the United States

BackgroundThe availability of feedstock options is a key to meeting the volumetric requirement of 136.3 billion liters of renewable fuels per year beginning in 2022, as required in the US 2007 Energy Independence and Security Act. Life-cycle greenhouse gas (GHG) emissions of sorghum-based ethanol need to be assessed for sorghum to play a role in meeting that requirement.ResultsMultiple sorghum-based ethanol production pathways show diverse well-to-wheels (WTW) energy use and GHG emissions due to differences in energy use and fertilizer use intensity associated with sorghum growth and differences in the ethanol conversion processes. All sorghum-based ethanol pathways can achieve significant fossil energy savings. Relative to GHG emissions from conventional gasoline, grain sorghum-based ethanol can reduce WTW GHG emissions by 35% or 23%, respectively, when wet or dried distillers grains with solubles (DGS) is the co-product and fossil natural gas (FNG) is consumed as the process fuel. The reduction increased to 56% or 55%, respectively, for wet or dried DGS co-production when renewable natural gas (RNG) from anaerobic digestion of animal waste is used as the process fuel. These results do not include land-use change (LUC) GHG emissions, which we take as negligible. If LUC GHG emissions for grain sorghum ethanol as estimated by the US Environmental Protection Agency (EPA) are included (26 g CO2e/MJ), these reductions when wet DGS is co-produced decrease to 7% or 29% when FNG or RNG is used as the process fuel. Sweet sorghum-based ethanol can reduce GHG emissions by 71% or 72% without or with use of co-produced vinasse as farm fertilizer, respectively, in ethanol plants using only sugar juice to produce ethanol. If both sugar and cellulosic bagasse were used in the future for ethanol production, an ethanol plant with a combined heat and power (CHP) system that supplies all process energy can achieve a GHG emission reduction of 70% or 72%, respectively, without or with vinasse fertigation. Forage sorghum-based ethanol can achieve a 49% WTW GHG emission reduction when ethanol plants meet process energy demands with CHP. In the case of forage sorghum and an integrated sweet sorghum pathway, the use of a portion of feedstock to fuel CHP systems significantly reduces fossil fuel consumption and GHG emissions.ConclusionsThis study provides new insight into life-cycle energy use and GHG emissions of multiple sorghum-based ethanol production pathways in the US. Our results show that adding sorghum feedstocks to the existing options for ethanol production could help in meeting the requirements for volumes of renewable, advanced and cellulosic bioethanol production in the US required by the EPA’s Renewable Fuel Standard program.

Impact of substrate overloading on archaeal populations in anaerobic digestion of animal waste

To characterize adaptive changes in methanogenic microbial community in response to substrate overloading and identify potential linkages between process performance and microbial community composition. Triplicate continuous anaerobic digesters were developed as model anaerobic digestion processes, which were subsequently disrupted by substrate overloading. The clone library analysis of archaeal communities experiencing substrate overloading showed that populations related to Methanosaeta were the dominant methanogens before and after substrate overloading, suggesting the functional importance of these acetoclastic methanogens in balanced anaerobic digestion processes characterized with low organic acids concentrations. Population redundancy in Methanosaeta increased following substrate overloading with the emergence of additional populations of Methanosaeta. More importantly, the methanogenic community responded to process imbalance with greater functional diversity with increased abundance of functionally distinct hydrogenotrophic and acetoclastic methanogens, which likely enhanced the functional stability of anaerobic digestion during disruptions in the anaerobic food web under process perturbation. Crenarchaeota were identified as persistent constituents of the archaeal communities in anaerobic digestion, warranting further efforts to identifying the functions of these phylogenetically distinct populations in anaerobic digestion. Substrate overloading in anaerobic digestion resulted in an increased functional diversity of the methanogenic community, which enhanced the capacity to overcome subsequent occurrences of process perturbations without performance disruption, providing a potential strategy to maintain process stability in anaerobic digestion. Anaerobic digestion is a sustainable option for waste treatment and renewable energy production. However, process instability resulting from variations in substrate loading has been one of the obstacles to the broader adoption of anaerobic digestion technology. Insight into the linkages between process performance and microbial community gained in this study is valuable for developing strategies for the mitigation of the impact of substrate overloading on anaerobic digestion processes.

The feasibility of a centralized biogas plant treating the manure produced by an organized animal farmers union in Turkey

The aim of this study is to evaluate the feasibility and the energy recovery potential of mesophilic (30-35 °C) anaerobic digestion of animal wastes (manure) at a centralized biogas plant (CBP) for 35,000 cattle. The proposed CBP is composed of an equalization tank followed by pasteurization and 3+[1/2] modules; i.e. each module consists of four completely mixed anaerobic reactors with a capacity of treating the manure from 10,000 cattle. The effect of maize silage loading, as the co-substrate, both on biomethane production and feasibility of the system was also evaluated. Besides, the transport fuel substitutes of the produced biomethane with or without co-substrate were also investigated. Results of the proposed CBP indicated that biomethane production increased ca. 1.65 fold with co-substrate addition and pay-back periods for one module treating 10,000 cattle manure are calculated to be ca. 11 and 7.0 yr without and with silage addition, respectively. Besides, considering the potential revenue when replacing transport fuels, about 74 heavy goods vehicles or 1,560 cars may be powered per year by the biogas produced from the proposed CBP where the co-digestion of manure and maize silage is applied.

Effects of cycle-frequency and temperature on the performance of anaerobic sequencing batch reactors (ASBRs) treating swine waste

Anaerobic digestion of animal waste is a technically viable process for the abatement of adverse environmental impacts caused by animal wastes; however, widespread acceptance has been plagued by poor economics. This situation is dismal if the technology is adapted for treating low strength animal slurries because of large digester-volume requirements and a corresponding high energy input. A possible technology to address these constraints is the anaerobic sequencing batch reactor (ASBR). The ASBR technology has demonstrated remarkable potential to improve the economics of treating dilute animal waste effluents. This paper presents preliminary data on the effects of temperature and frequency-cycle on the operation of an ASBR at a fixed hydraulic retention time (HRT). The results suggest that within the parameter range under consideration, temperature did not affect the biogas yield significantly, however, higher cycle-frequency had a negative effect. The biogas quality (%CH 4) was not significantly affected by temperature nor by the cycle-frequency. The operating principle of the ASBR follows four phases: feed, react, settle, and decant in a cyclic mode. To improve the biogas production in an ASBR, one long react-phase was preferable compared to three shorter react-phases. Treatment of dilute manure slurries in an ASBR at 20 °C was more effective than at 35 °C; similarly more bio-stable effluents were obtained at low cycle-frequency. The treatment of dilute swine slurries in an ASBR at the lower temperature (20 °C) and lower cycle-frequency is, therefore, recommended for the bio-stabilization of dilute swine wastewaters. The results also indicate that significantly higher VFA degradation occurred at 20 °C than at 35 °C, suggesting that the treatment of dilute swine slurries in ASBRs for odor control might be more favorable at the lower than at the higher temperatures examined in this study. Volatile fatty acid reduction at the two reactor temperatures and cycle-frequencies, from a high of 639 ± 75 mg/L to a low of 92 ± 23 mg/L, greatly reduced the odor and the odor-generation potential in post-treatment storage. The nutrients (both N and P) in the waste influent were conserved in the effluents.

06/02003 Anaerobic digestion of animal waste: effect of mixing: Karim, K. et al. Bioresource Technology, 2005, 96, (14), 1607–1612

06/02003 Anaerobic digestion of animal waste: effect of mixing: Karim, K. et al. Bioresource Technology, 2005, 96, (14), 1607–1612