Anaerobic Co-digestion Of Dairy Manure Research Articles

Pyrolysis kinetics of new bioenergy feedstock from anaerobic digestate of agro-waste by thermogravimetric analysis

In this study, thermogravimetric and kinetic analysis of digestate from anaerobic co-digestion of dairy manure and dry biomass of Amaranthus retroflexus L. is presented. Thermal decomposition of digestate was studied in the temperature range 40–1000 °C in an inert atmosphere using thermogravimetric and differential scanning calorimetry (TG-DSC) at the heating rates of 5, 10, 15 and 20 °C/min. According to the results of TG/DTG analysis, the thermal decomposition of digestate occurs in three stages: dehydration, devolatilization and decomposition of carbonaceous residue. The devolatilization stage in pyrolysis is a key stage; therefore, it was divided into two steps: I-st step and II-nd step and analyzed in detail. The kinetic parameters were estimated by isoconversion Friedman, OFW (Ozawa-Flynn-Wall) and KAS (Kissinger-Akahira-Sunose) methods and using model-based methods, such as CnB (reaction of n-th order with autocatalysis by product), Bna (expanded Prout-Tompkins equation) and Fn (the reaction of n-th order). For the model-free methods, the average Eα values for the I-st step were 136.3 kJ/mol and for the II-nd step 143.1 kJ/mol. The average Eα values obtained using the CnB, Bna, and Fn models were 105.8 kJ/mol for the I-st step and 145.6 kJ/mol for the II-nd step, i.e. Eα increased by 37.6%. The results of the evaluation of the thermal behavior of digestate from agro-waste indicate a good prospect for the use of biomass as a new bioenergy feedstock. The obtained kinetic parameters are of great importance for the design of pyrolysis reactors.

Anaerobic co-digestion of dairy manure and maize stover with different total solids content: From the characteristics of digestion to economic evaluation

The objective of the present study is to assess the effect of the total solids (TS) content on the digestion performance, methanogenic pathways, and economic evaluation of anaerobic co-digestion with dairy manure and maize stover. The results showed that the cumulative methane yields decreased with increasing TS content, which was consistent with the maximum methane production rate and hydrolysis rate. The pH, alkalinity, soluble chemical oxygen demand, ammonium nitrogen, and volatile fatty acid content increased with increasing TS content. Analysis of the microbial community showed that the abundance of Methanosaeta decreased and Methanosarcina increased with increasing TS content, which led to the succession of the methanogenesis pathway from the acetoclastic pathway to the mixotrophic and hydrogenotrophic pathways. Results of the economic analysis indicated that the profitability of AD system increased with increasing TS content, resulting in more solid digestate being produced under the analysis conditions.

Pilot Scale Solid State Anaerobic Co-digestion of Dairy Manure and Milking Parlor Wastewater

A pilot scale solid-state anaerobic co-digestion study was conducted to elucidate the feasibility of anaerobic digestion as an effective treatment method for dairy manure (DM) and milking parlor wastewater (MPW), and it focusing mainly on the stability of anaerobic digestion process and methane production potential. Dairy manure and milking parlor wastewater were co-digested (1/0.48, w/w) in 11m3 volume reactor for 63days at the mesophilic condition (36°C). In addition, pH, volatile fatty acids and ammonia were periodically analyzed to monitor anaerobic digestion inhibitions. The results showed that the co-digestion of DM and MPW was successfully performed without any inhibition caused by ammonia and volatile fatty acids accumulation. The potential methane production (P) from a modified Gompertz model was about 130.5 mL g-VS-1, and approximately 80% of the methane production was obtained during the 40 days digestion test and the lag phase was 14 days. The pilot scale SSAD (solid-state anaerobic digestion) system showed about 1.3-fold higher methane production than lab-scale system. The results of solid-state anaerobic co-digestion of bedded pack barn dairy manure and milking parlor wastewater using pilot-scale anaerobic digester can be used as a reference for the design of farm-scale anaerobic digester. The pilot scale SSAD system showed about 1.3-fold higher methane production than lab-scale system. The potential methane production (P) was about 130.5 mL g-VS-1, and approximately 80% of the methane production was obtained during the 40 days digestion test and the lag phase was 14 days.

Improving performance and phosphorus content of anaerobic co-digestion of dairy manure with aloe peel waste using vermiculite

Phosphorus content of the digestate is crucial for evaluating its fertilizer utilization in anaerobic digestion system. The vermiculite containing rich-phosphorus is firstly used as an accelerant in anaerobic batch co-digestion system of aloe peel waste and dairy manure. After introducing vermiculite, the cumulative biogas production (295.14–353.96 mL/g VS), chemical oxygen demand removal rate (45.53%–71.03%), and volatile solid removal rate (50.70%–52.76%) are remarkably higher than those of reference reactor (234.08 mL/g VS, 39.38%, 45.10%). The thermal and fertility analyses manifest the digestates with vermiculite possess superior stability, admirable fertilizer values (5.97%–6.81%), and excellent total phosphorus content (11.44–13.29 g/kg). The improved co-digestion performance can be attributed to the addition of vermiculite. This work introduces a novel approach for improving the performance of anaerobic co-digestion and the fertilizer utilization of digestate in the co-digestion systems.

Nutrient and Pathogen Suppression Properties of Anaerobic Digestates from Dairy Manure and Food Waste Feedstocks

Anaerobic co-digestion of dairy manure and food wastes is increasing in the New England region of the United States because of policy measures intended to divert organic materials from landfills, reduce greenhouse gas emissions, and increase renewable biogas energy production. The sustainability of this approach depends on the management and valorization of remaining solid and liquid residues (i.e., digestates) after anaerobic digestion. Few studies have characterized digestates derived from combined dairy manure and food waste feedstocks. In this study, we analyzed screw-press separated liquid and solid digestates from 6 of 26 (23%) operational full-scale facilities in New England. We quantified multiple pools of nitrogen and phosphorus in these materials, with results suggesting that, in most cases, these nutrients largely exist in forms that can be recycled via slow-release fertilization, with smaller fractions in forms more easily lost to the environment. Furthermore, we found that solid digestates can inhibit mycelial growth of a common soilborne fungal pathogen, Rhizoctonia solani, suggesting potential to manage resident soil pathogens. Capitalizing on both nutrient recycling and pathogen suppression co-benefits will likely be useful in digestate valorization efforts.

Integrating anaerobic co-digestion of dairy manure and food waste with cultivation of edible mushrooms for nutrient recovery

State-level policies in the New England region of the United States require diversion of organic materials away from landfills. One management option for food waste is anaerobic co-digestion with dairy manure. In addition to biogas, anaerobic digestion produces separated solid and liquid digestates. Solid digestates in the region are typically recycled as animal bedding before returning to the digester and liquids are used to fertilize local soils. Repeated land application of nutrients can contribute to eutrophication risk over time and alternative models are needed to convert digestates into valuable export products. We tested solid digestates derived from dairy manure and food waste as substrate ingredients in the cultivation of Pleurotus ostreatus. We show these materials can be used to offset non-local substrate ingredients while achieving mushroom yields comparable to commercial recipes. This strategy could help divert nutrients away from land adjacent to digesters and into safe, protein-rich food, while producing useful spent mushroom substrate.

Reactor performance and economic evaluation of anaerobic co-digestion of dairy manure with corn stover and tomato residues under liquid, hemi-solid, and solid state conditions

Anaerobic co-digestion of tomato residues, dairy manure, and corn stover at ratios of 20:48:32, 40:36:24, and 60:24:16 (volatile solid basis) were compared for liquid anaerobic digestion (L-AD), hemi-solid state AD (HSS-AD), and solid state AD (SS-AD) systems. The highest methane yield (353.5 L/kg-VSadded) and volumetric methane productivity (24.5 m3methane/m3reactor volume) were both obtained with 20% tomato residues addition under L-AD and HSS-AD conditions, respectively. Total solid and feedstock mixing ratio affected the degradation of protein and lipids during AD, but not cellulose and hemicellulose. Economic analysis results indicated that capital and labor costs have the dominant effect on total investment. SS-AD of tomato residues, dairy manure, and corn stover at ratios of 20:48:32 (VS basis) has the highest net present value (2.6 million US$) and shortest payback period (10.1 year), which indicated SS-AD was financially attractive under analysis conditions.

Semi-continuous anaerobic co-digestion of dairy manure, meat and bone meal and crude glycerol: Process performance and digestate valorization

Abstract The objective of this study was to investigate the effects of the addition of meat and bone meal (MBM) and crude glycerol (CG) on the anaerobic digestion of dairy manure (DM) with respect to digestion performance and digestate fertilizer value. The anaerobic co-digestion of DM, MBM and CG was conducted in semi-continuous stirred tank reactors at 37 °C with organic loadings between 2.63 and 2.86 g volatile solids (gVS)/L·d. Run 1 was a control reactor, while in Runs 2 and 3, DM was co-digested with MBM at ratios of 3.0:1.0 and 1.0:1.0 (gVSDM:gVSMBM), respectively. In Run 4, DM and MBM were co-digested with CG at a ratio of 1.0:0.7:0.3 (gVSDM:gVSMBM:gVSCG). The results showed that methane yields were increased by 9.1% and 30.2% in Runs 2 and 3, respectively, compared to Run 1, while the highest methane yield (0.39 L/gVSadded·d) was obtained in Run 4. The co-digestion of DM with MBM increased the ammoniacal nitrogen in the digestate by 2.1- to 2.3-fold, while no significant difference was observed for phosphorus. Due to the overabundance of nutrients in soil, the recovery of phosphorus and nitrogen and the recycling of water are the best strategies to sustain anaerobic digestion via an environmentally friendly approach.

Reactor performance and energy analysis of solid state anaerobic co-digestion of dairy manure with corn stover and tomato residues

Anaerobic co-digestion is commonly believed to be benefical for biogas production. However, additional of co-substrates may require additional energy inputs and thus affect the overall energy efficiency of the system. In this study, reactor performance and energy analysis of solid state anaerobic digestion (SS-AD) of tomato residues with dairy manure and corn stover were investigated. Different fractions of tomato residues (0, 20, 40, 60, 80 and 100%, based on volatile solid weight (VS)) were co-digested with dairy manure and corn stover at 15% total solids. Energy analysis based on experimental data was conducted for three scenarios: SS-AD of 100% dairy manure, SS-AD of binary mixture (60% dairy manure and 40% corn stover, VS based), and SS-AD of ternary mixture (36% dairy manure, 24% corn stover, and 40% tomato residues, VS based). For each scenario, the energy requirements for individual process components, including feedstock collection and transportation, feedstock pretreatment, biogas plant operation, digestate processing and handling, and the energy production were examined. Results showed that the addition of 20 and 40% tomato residues increased methane yield compared to that of the dairy manure and corn stover mixture, indicating that the co-digestion could balance nutrients and improve the performance of solid-state anaerobic digestion. The energy required for heating substrates had the dominant effect on the total energy consumption. The highest volatile solids (VS) reduction (57.0%), methane yield (379.1 L/kg VSfeed), and net energy production were achieved with the mixture of 24% corn stover, 36% dairy manure, and 40% tomato residues. Thus, the extra energy input for adding tomato residues for co-digestion could be compensated by the increase of methane yield.

Anaerobic co-digestion of dairy manure, meat and bone meal, and crude glycerol under mesophilic conditions: Synergistic effect and kinetic studies

Anaerobic digestion is a potential renewable energy, climate independent and robust technology, which is able to treat different kinds of organic wastes and by-products. This study investigated the anaerobic co-digestion of meat and bone meal (MBM) with dairy manure (DM) and crude glycerol (CG). Three sets of batch experiments were conducted at mesophilic condition; one set of anaerobic mono-digestion and two sets of anaerobic co-digestion. In experiment I, each substrate was mono-digested at inoculum to substrate ratio of 1. In experiment II, MBM and DM were co-digested at ratios of 1.0:1.0, 1.0:2.0, 1.0:1.0, and 2.0:1.0, while in experiment III CG was co-digested with MBM at ratios of 1.0:3.0, 1.0:1.0 and 3.0:1.0, at a fixed amount of DM. The results of anaerobic mono-digestion showed that CG produced the highest methane yield (0.48L/gVS) followed by MBM (0.41L/gVS) and DM (0.17L/gVS). In the anaerobic co-digestions, methane yield increased with the increase of MBM content, while it increased together with CG content. The kinetic studies showed that the physico-chemical characteristics of the co-digested substrates influenced hydrolysis rate constant and lag-phase, which increased with the increase of CG content. However, synergistic effect was decreased when MBM content was increased, whereas the opposite was observed to that with CG. Therefore, carbon to nitrogen ratio was an important parameter determining synergistic effect in anaerobic co-digestion, while the physico-chemical characteristics influenced the hydrolysis rate constant and lag-phase.

Two-phase anaerobic co-digestion of dairy manure with swine manure

In order to solve the problems associated with high fiber content, and the ensuing lower biogas volume yield in anaerobic digestion of dairy manure, a study of the co-digestion of separated liquids from dairy manure combined with swine manure using a two-phase anaerobic digestion process was conducted. The influence of level of total solids (TS) and hydraulic retention time (HRT) of the mixed liquor on the specific methane production were studied. Three TS levels 8%, 10% and 12% were investigated. Analysis of the results show that a maximum specific methane yield of 132.99 L/kg volatile solids (VS), can be obtained with a TS of 9%, an inoculation rate of 30%, the duration of hydrolytic acidification phase of 5 d, and an HRT of the methanogenic phase of 10 d. These findings could provide directions for improving the biogas production by performing the co-digestion of dairy manure with swine manure. Keywords: co-digestion, two-phase anaerobic digestion, dairy manure, swine manure, biogas DOI: 10.3965/j.ijabe.20160902.1637 Citation: Guan Z J, Sun X L, Bi L P, Li W Z, Zhang Y, Wang Z G. Two-phase anaerobic co-digestion of dairy manure with swine manure. Int J Agric & Biol Eng, 2016; 9(2): 146－152.

The effect of cefazolin on biogas production from thermophilic and mesophilic anaerobic co-digestion of dairy manure and waste milk

Antibiotic residues in animal waste from concentrated animal feeding operations are of considerable concern because of the potential development of antibiotic resistant bacteria in the environment and the effect of these residues on manure treatment systems. The objective of this study was to determine the effect of cefazolin (10 mg L-1) during thermophilic and mesophilic anaerobic co-digestion of manure and waste milk from cows treated with cefazolin for mastitis. The collected antibiotic free manure samples were mixed with slurry and milk obtained from a healthy cow accordingly to form manure mixture (slurry 50 % and manure 50 %) and milk mixture (slurry 50 %, manure 45 % and milk 5 %), each of which was further separated as the control and cefazolin spiked (10 mg L-1), loaded into triplicate 1 L batch digesters and anaerobically digested at 37 °C and 55 °C for 22 days separately. Control and cefazolin spiked milk mixtures always produced significantly (p 0.05) differences in total and methane gas yields were observed in the respective cefazolin spiked digesters despite the temperature at which the digestion was carried out. Volatile fatty acid (VFA) accumulation and reduction of pH were not observed in any digester of both substrates at both temperatures at the end of the experiment, which confirmed the process stability. However, further investigations are necessary to analyse the effects of increased concentrations of cefazolin in the substrates on digester stability. J.Natn.Sci.Foundation Sri Lanka 2015 43 (4):369-376

Life Cycle and Economic Assessment of Anaerobic Co-digestion of Dairy Manure and Food Waste

Abstract A comprehensive life cycle and financial analysis was conducted to evaluate the environmental and economic performance of an anaerobic co-digestion system for dairy manure and food wastes versus a control system that anaerobically digests dairy manure but landfills food wastes. The environmental impacts of co-digestion are lower than the control system for global warming (66.95%), water eutrophication (18.88%), and smog emission (68.93%), but higher for air acidification (39.38%). Co-digestion results in a net energy ratio that is 1.67 times higher than the control system. An economic analysis revealed that co-digestion is more profitable, as the calculated 25-year net value of over $8.4 million is far superior to the -$7.5 million for the control system. Considering both environmental impacts and economic indicators, manure and food waste co-digestion is a preferable solution for waste management and bioenergy production.

Evaluation of anaerobic co-digestion of dairy manure with food wastes via bio-methane potential assay and CSTR reactor

The introduction of food wastes into anaerobic digestion (AD) brings a promising scenario of increasing feedstock availability and overall energy production from AD. This study evaluated the biodegradability and methane potential from co-digestion of two typical food wastes, kitchen waste and chicken fat, with dairy manure. For single substrate, the bio-methane potential assays showed that kitchen waste had the highest methane yield of 352 L-CH4 kg–1-VS added, 92% more than dairy manure alone. Chicken fat at the same Volatile Solid (VS) level (2 g L–1) inhibited bio-methane production. Addition of kitchen waste and chicken fat to a VS percentage of up to 40% improved overall methane yield by 44% and 34%, respectively. Synergistic effect was observed when either combining two or three substrates as AD feedstock, possibly as a result of increased biodegradability of organic materials in chicken fat and kitchen waste compared with dairy manure. Addition of chicken fat improved methane yield more than kitchen waste. However, addition of chicken fat VS over 0.8 g L–1 should be cautiously done because it may cause reactor failure due to decrease in pH. The maximum methane yield was 425 L-CH4 kg–1-VS, achieved at a VS ratio of 2:2:1 for kitchen waste, chicken fat, and dairy manure. Results from batch AD experiment demonstrated that supplementing dairy manure to chicken fat and/or kitchen waste improved alkalinity of substrate due to the inclusion of more titratable bases in dairy manure, and therefore stabilized the methanogenesis and substantially improved biogas yield. A mixture of substrates of kitchen waste, chicken fat, and dairy manure at a ratio of 1:1:3 was fed to a continuously stirred tank reactor operated at organic loading rates of 3.28, 6.55, and 2.18 g-COD L–1-day (hydraulic retention time of 20, 10, and 30 days, respectively) under mesophilic condition, and methane production rate reached 0.65, 0.95, and 0.34 L-CH4 L–1-reactor-day.

Effects of temperature and carbon-nitrogen (C/N) ratio on the performance of anaerobic co-digestion of dairy manure, chicken manure and rice straw: focusing on ammonia inhibition.

Anaerobic digestion is a promising alternative to disposal organic waste and co-digestion of mixed organic wastes has recently attracted more interest. This study investigated the effects of temperature and carbon-nitrogen (C/N) ratio on the performance of anaerobic co-digestion of dairy manure (DM), chicken manure (CM) and rice straw (RS). We found that increased temperature improved the methane potential, but the rate was reduced from mesophilic (30∼40°C) to thermophilic conditions (50∼60°C), due to the accumulation of ammonium nitrogen and free ammonia and the occurrence of ammonia inhibition. Significant ammonia inhibition was observed with a C/N ratio of 15 at 35°C and at a C/N ratio of 20 at 55°C. The increase of C/N ratios reduced the negative effects of ammonia and maximum methane potentials were achieved with C/N ratios of 25 and 30 at 35°C and 55°C, respectively. When temperature increased, an increase was required in the feed C/N ratio, in order to reduce the risk of ammonia inhibition. Our results revealed an interactive effect between temperature and C/N on digestion performance.

Modeling of the methane production and pH value during the anaerobic co-digestion of dairy manure and spent mushroom substrate

A dynamic mathematical model, based on the IWA Anaerobic Digestion Model No. 1 (ADM1), was used to predict the methane production and pH value during anaerobic co-digestion of dairy manure (DM) and spent mushroom substrate (SMS) under different hydraulic retention times (HRT). In this model the degradation of DM was modeled according to classical ADM1, while SMS was divided into inert part as well as biodegradation parts of slowly hydrolysable fraction (SHF) and readily hydrolysable fraction (RHF). The data from lab-scale experiment was used to calibrate and validate this model. The results showed that the model was able to predict reasonably well the steady-state results of methane production and pH value at HRT of 12, 20 and 28 d. The results also indicated that the model suitability to assess the combined effects of HRT and substrate ratio on the methane production and pH value.

Semi-continuous anaerobic co-digestion of dairy manure with three crop residues for biogas production

The characteristics of anaerobic semi-continuous co-digestion of dairy manure (DM) with three crop straw residues (SRs), rice straw, corn stalks and wheat straw under five mass mixing ratios (SRs/DM) were investigated. During the anaerobic digestion (AD) process, four periods were identified: startup, first stage of stabilization, second stage of stabilization, and suppression. Following the four periods, the biogas production rate varied between 101 and 576mL L(-1)d(-1). A high CH4 content and volatile solid reduction was maintained at the SRs/DM mass mixing ratio 1:9. The highest cumulative biogas production of more than 19L was obtained at ratio 5:5. However, ratio 9:1 performed worst in the whole process. Systematic analysis of the elements revealed nitrogen, phosphorus, and trace elements contents were important for the AD. Overall, the semi-continuous AD is efficient within a wide range of SRs/DM mass mixing ratios.

Effects of corn stover as carbon supplement on an integrated anaerobic digestion and ethanol fermentation process

An integrated anaerobic digestion (AD) and ethanol fermentation process on a mixed feedstock of dairy manure and corn stover was performed to investigate the influence of corn stover on biogas production, lignocellulose decomposition efficiency, and ethanol production of the digested fiber (AD fiber). Addition of corn stover not only promoted the biogas production but also enhanced ethanol production from AD fiber. A 20% addition of corn stover increased the methane production from a semi-continuous anaerobic co-digestion by 14% compared to the digestion of dairy manure only, and the cellulose utilization efficiency of AD fiber from the co-digestion was significantly (p < 0.05) higher than that from manure digestion. The net energy production, including both anaerobic co-digestion and bioethanol production, was increased from 8017 to 9573 kJ kg−1 dry raw feed. The results indicated that anaerobic co-digestion of dairy manure and corn stover can significantly enhance feedstock utilization efficiency and improve the energy balance of the integrated anaerobic digestion and ethanol fermentation process.

Anaerobic co-digestion of dairy cow manure and high concentrated food processing waste

Anaerobic co-digestion of dairy manure (DM) and concentrated food processing wastes (FPW) under thermophilic (55 °C) and mesophilic (35 °C) temperatures, and fertilizer value of the effluent were investigated in this study. Two types of influent feedstock were utilized: 100 % DM and a 7:3 mixture (wet weight basis) of DM and FPW. The contents of the FPW, as feedstock were 3:3:3:1 mixture of cheese whey, animal blood, used cooking oil and residue of fried potato. Four continuous digestion experiments were carried out in 10 L digesters. Co-digestion under thermophilic temperature increased methane production per digester volume. However, co-digestion at 35 °C was inhibited. Total Kjeldahl nitrogen (N) recovered after digestion ranged from 73.1 to 91.9 %, while recoveries of ammonium nitrogen (NH4-N) exceeded 100 %. The high recovery of NH4-N was attributed to mineralization of influent organic N. The mixture of DM and FPW showed greater recoveries of NH4-N after digestion compared to DM only, reflecting its greater organic N degradability. The ratios of extractable to total calcium, phosphorus and magnesium were slightly reduced after digestion. These results indicate that co-digestion of DM and FPW under thermophilic temperature enhances methane production and offers additional benefit of organic fertilizer creation.

Prospect of anaerobic co-digestion of dairy manure: a review

Dairy manure is an abundant waste in dairy farming and poses handling, storage and disposal challenges. With poor management, dairy manure produces odour, ammonia and releases greenhouse gases that contribute to global warming. Anaerobic digestion (AD) is a means to produce renewable energy and to reduce environmental impacts resulting from improper management of dairy manure. Dairy manure AD suffers from low biogas production per unit mass, hence it is costly per unit volume. To improve biogas production per unit volume, anaerobic co-digestion of dairy manure is one of the methods used to enhance biogas production. This article reviews various approaches and challenges of co-digestion to enhance biogas production and methane yield that have been used in the last decade. Substrate selection and prediction of biogas production based on chemical oxygen demand are the main areas of focus. Process inhibition by co-substrates is also examined.