Anaerobic Digestion Of Organic Matter Research Articles

Implementación de Biodigestores para el aprovechamiento de residuos en pequeñas unidades productivas agropecuarias

In isolated areas that are difficult to access for energy interconnection, it is necessary the production of alternative energies highlighting biomethane which is generated from the anaerobic digestion of organic matter. The objective of this document is to present some results of an intervention experience in 6 agricultural production units located in villages near the city of Fusagasugá, in which biodigesters were developed to improve the conditions of energy production under environmental sustainability parameters. For the selection of the 6 productive units, there were analyzed the conditions of 21 productive units from 13 villages near the city of Fusagasugá, referenced by the Sumapáz livestock committee. The analysis was based on the availability of waste in accordance with the requirements for the proper functioning of the biodigesters, and the willingness of the owners for the implementation of biodigesters as energy complementarity in small agricultural units. Among the most relevant results, it was found that there are drawbacks of adopting this type of alternative energy in rural productive units with the decision of only 6 properties from the 21 productive units consulted representing 28,5%, situation that shows some challenges related to strategies to connect isolated rural populations with the implementation of biodigesters as complementary energy in small agricultural units.

Enhanced Anaerobic Digestion Using Conductive Materials through Mediation of Direct Microbial Interspecies Electron Transfer: A Review

The anaerobic digestion (AD) of organic matter is susceptible to the challenges posed by low-speed electron transfer between microorganisms and the limitation of low hydrogen partial pressure, resulting in low methane recovery efficiency and poor system stability. Numerous studies in recent years have shown that a variety of conductive materials can significantly increase the interspecies electron transfer (IET) rate, optimize the structure and function of anaerobic microbial communities, improve methane yield, and promote system stability by mediating the direct interspecies electron transfer (DIET) of reciprocal microorganisms. In this study, on the basis of investigating the IET mechanism of methanogenic microorganisms in the AD of organic matter, the effects of carbon-based conductive materials (activated carbon, biochar, carbon cloth, carbon fiber, graphite, graphite felt, graphene, and carbon nanotubes) and iron-based conductive materials (magnetite, Fe3O4, hematite, Fe2O3, goethite, and zero-valent iron) on AD performance and microbial community using DIET are reviewed. Future research should focus on establishing an evaluation system, identifying flora with DIET potential, and finding methods for engineering applications that increase recovery efficiency and reveal the principle of conductive materials to mediate DIET.

Model development for biogas generation, purification and hydrogen production via steam methane reforming

Biogas, a renewable energy source produced by the anaerobic digestion of organic matter, can reduce greenhouse gas emissions. The purification and hydrogen conversion of biogas enhance its versatility as an energy carrier and reduce dependency on fossil fuels. This sustainable process fosters a cleaner future. In this study, simulation models were used to optimize the process conditions and assess the technical feasibility of the biogas-to-hydrogen production. In addition to the anaerobic digestion process, simulation models were also developed for biogas purification via water scrubbing and hydrogen production via steam methane reforming (SMR) using Aspen Plus simulation software. Simulation results demonstrated that the maximum methane yield of 520 mL/gVS was achieved at an organic loading rate of 20 g/L, while the minimum yield of 230 mL/gVS was observed below 10 g/L. Optimal anaerobic digestion temperature for maximum gas yield (548 mL/gVS) was found to be 30 °C, with a decrease in biogas production above 40 °C. In the water scrubbing model, maximum CO2 absorption occurred at 15 bar pressure, whereas reducing the pressure to 5 bar significantly lowered the absorption rate. The SMR model yielded the highest hydrogen production rate of 10.15 kg/h using purified methane (99%) as feed, but the methane content was affected by the biogas composition.

The Effect of Various Parameters on Sustainable Biogas Production

This research study aimed to examine the effect of various parameters on sustainable biogas production through the anaerobic digestion of organic matter. A laboratory-scale biogas digester was used to evaluate the impact of different feedstock compositions, temperatures, pH levels, retention times, mixing and agitation, inoculum, and operating conditions on biogas production efficiency and yield. Biogas yield, quality, and composition were measured and analyzed to identify the optimal conditions for sustainable biogas production. The results of the study indicated that feedstock composition, temperature, pH, retention time, mixing and agitation, inoculum, and operating conditions all had significant impacts on biogas production efficiency and yield. Specifically, feedstock composition and retention time were found to be the most critical factors affecting biogas production. A high carbon-to-nitrogen (C:N) ratio in the feedstock and longer retention times were associated with higher biogas yields. The findings of this study have important implications for the development of more efficient and sustainable biogas production systems. By optimizing the various parameters involved in biogas production, it is possible to improve the efficiency and yield of biogas production, while minimizing environmental impact. This research contributes to the growing body of knowledge on sustainable energy generation and waste management, and highlights the potential of biogas production as a renewable energy source

Thermophilic Anaerobic Digestion: An Advancement towards Enhanced Biogas Production from Lignocellulosic Biomass

Thermophilic anaerobic digestion (TAD) technology has been adopted worldwide mainly due to it being a pathogen-free process in addition to the enhanced biogas yield and short hydraulic retention time (HRT). Taking the high metabolic rate of the thermophilic microbial community with highly efficient enzymatic systems into consideration, thermophiles are being widely explored as efficient inocula for lignocellulosic biomass (LCB) degradation and improved biomethane production. The advantages of TAD over mesophilic anaerobic digestion (MAD), including improved kinetics, efficient degradation of organic matter, and economic and environmental sustainability, make it one of the best strategies to be operated at moderately high temperatures. This review sheds light on the relevant role of thermophilic microorganisms as inocula in the anaerobic digestion of organic matter and factors affecting the overall process stability at high temperatures. Further, the discussion explains the strategies for enhancing the efficiency of thermophilic anaerobic digestion.

Comparison between different parameters for anaerobic digestion technologies

Due to the increased demand for energy and the near depletion of fossil fuel sources, in addition to the problems of global warming, the world has turned to renewable energy sources as an alternative solution. One energy source is the anaerobic digestion of organic matter, such as animal or food waste. Biogas is produced from this process, used to generate electricity and heat, or processed for use as a transportation fuel and compost production for agriculture. This process is affected by many factors like the potential of hydrogen (PH), temperature, carbon/nitrogen ratio (C/N), and other factors. Dry anaerobic digestion has higher total solid content (TS) than wet anaerobic digestion. On the other hand, it has lower maintenance and construction costs compared with wet anaerobic digestion. In this research, we will highlight the operational conditions of the process in addition to its different types. It also contains an overview of this system, its working principle, its advantages, and the system component and show the best ways to improve its efficiency.

A Brief History of Biogas in Nepal: Lessons for the Future from the Past

Biogas, a gaseous mixture resulted from anaerobic digestion of organic matter, is an alternative source of energy that contributes to circularity. This paper introduces biogas and briefs its history in the context of Nepal. Despite being used as early as the 10th century BC, biogas only caught proper attention since the dawn of the industrial revolution. Meanwhile, biogas technology started its development only in the late-mid 19th century whilst taking a hundred more years for Nepal to follow suit. Since the construction of the first biogas plant in 1960, Nepal has introduced several plans and policies with the help of private and international agencies to construct about half a million biogas plants as of 2021. The major turning point in the history of biogas in Nepal came in 1992 with the initiation of Biogas Support Program which coincided with the then His Majesty Government of Nepal’s ambitious eight 5-year plan. The future policymakers are suggested to keep the growing urban population in mind whilst making new deals and policies to promote and facilitate biogas technology.

COMPARATIVE EVALUATION ON THE POTENTIALS OF SHEEP RUMEN CONTENTS FOR BIOGAS GENERATION

Biogas refers to a gas produced by the biological breakdown of organic matter in the absence of oxygen. It is as a clean biofuel produced by microorganism during anaerobic digestion of organic matter. The study was carried out to determine the potentials of sheep rumen contents for biogas production through anaerobic digestion. Proximate analysis was carried out on the substrate. The results shows that nitrogen, potassium and phosphorus have 0.58 ± 0.02 (mg/ml), 425 ± 5.00 (mg/ml), and 2.57 ± 0.03 (mg/ml) respectively. After proximate analysis, four (4) local digesters with capacity of 500g tins were designed and used for the collection of gas via passage pipe systems. The digesters were used to digest the slurry (mixture of Sheep rumen content and water) which were mixed in the ratio of 2:1 for a period of eight weeks (56 days) retention time until the biogas reduced significantly. The pH values of the slurries were adjusted to neutral. The digesters were stirred thrice daily to avoid scum formation in the digesters and allow for easy escape of gas produced. The total average yield of the gas produced were 820 cm3, 1070 cm3, 780 cm3, and 660 cm3 for D1, D2, D3, and D4 respectively. Isolation of Microorganisms were caried during the production where B. subtilis, E. coli, P. aeruginosa, and S. aureus were found. Biogas production from organic wastes which is an eco-friendly, which helps to solve most countries energy crisis.

Co-digestion of euryhaline microalgae Scenedesmus sp. MKB. with paddy straw for biogas production

Biogas is a clean and renewable biofuel source produced by anaerobic digestion of organic matter and can replace conventional sources of energy such as fossil fuels. The present study was undertaken to assess biogas production from microalgae Scenedesmus sp. MKB. (MN796425) which was isolated from the saline water collected from the waterlogged area of Southwest Punjab. The biogas production for different concentrations of microalgal biomass, microalgal filtrate, and paddy straw was observed in laboratory conditions and the performance of microalgae was also studied in field conditions. The co-digestion of microalgal biomass and paddy straw under laboratory conditions revealed maximum production of 60.18 L when both were co-digested as compared to 48.56 L during the digestion of paddy straw alone. Kinetics of biogas production studied by modified Gompertz equation revealed that the highest biogas production potential (P) of 68.58 mLg-1 volatile solids at the biogas production rate (Rm) of 1.34 mLg-1d-1 with lag phase (λ) of 0.66 days. Microalgae biomass production under field conditions was carried out in an open raceway pond of 200 L capacity and later biomass was digested in 1 m3 digester that showed cumulative biogas production of 2,407 L and it was 20.44% more than control.

Estimating the potential of energy generation by anaerobic digestion of slaughterhouse wastes toward sustainable waste management strategy: a case study

ABSTRACT While producing and consuming vast amounts of energy, Iran has lagged behind its peers in the use of renewable energies, such as bioenergy. The present study was an attempt to estimate the potential of energy generation by the anaerobic digestion of organic matter produced in Iranian slaughterhouses, recruiting a waste-management and greenhouse gas (GHG) emission reduction approach. Accordingly, the type and amount of slaughterhouse wastes (SHWs) produced in different provinces were identified, and then the potential of methane (CH4) production at the provincial and national scales was estimated. The results showed that, theoretically, there was the potential for producing 111 million cubic meters per year (m3/yr) of CH4 from SHWs, which, if fed into combined heat-power (CHP) plants, could ideally produce 1,004 gigawatt-hour (GWh) of electricity. This would also enhance the share of renewable resources in Iran’s total energy supply by 4%. Exploiting biogas produced by anaerobic digestion instead of traditional fossil fuels would thus reduce Iran’s annual carbon dioxide (CO2) emissions by 482,000 tonnes. Correspondingly, the economic analysis of the energy and social costs of CO2 emissions revealed that energy generation by the anaerobic digestion of SHWs could lead to an annual cost-saving of about $102 million.

Biogas Production in Laboratory Scale from Different Organic Wastes Using Primary Sludge as Co-substrate

Biogas production technology not only constitutes a biofuel source, but also can be a mitigation measure for the various environmental pollutants. This technology, i.e., anaerobic digestion is a biological process that takes place naturally when microorganisms break down organic matter in the absence of oxygen. In an enclosed chamber, controlled anaerobic digestion of organic matter produces biogas which is predominantly methane. The produced methane then can be directly used; or after certain conditioning, can be used in onsite power generation, heating homes or as vehicular fuel. Besides, organic waste is increasingly becoming a major problem in every society imposing serious economic and environmental concerns. For this reason, many contemporary researches are emphasizing in finding sustainable solutions to recycle and produce energy from such waste. In this context, this paper aims to investigate the potential of cow and chicken manure, and olive waste for biogas production obtained through the anaerobic digestion process.
 The substrates were placed in laboratory scale digesters without pretreatment. The retention time in the digesters was 30 days. The samples of the tested substrates were collected and analyzed for pH, total solids, ash, and the content of volatile solids (VS). Under mesophilic conditions, all combinations of cow and chicken manure, and olive waste with sludge by an anaerobic pond of a trickling filter treatment plant, as co-substrate, significantly improved biogas, and methane yields. The experimental results showed that chicken manure (CM) is the most suitable for anaerobic digestion (AD).
 The next step of the study will consist in implementing a large scale of biogas production plants and we will estimate the national potential of green energy produced by this technology and map the areas that need digesters.

Biogas Production in Laboratory Scale from Different Organic Wastes Using Primary Sludge as Co-substrate

Biogas production technology not only constitutes a biofuel source, but also can be a mitigation measure for the various environmental pollutants. This technology, i.e., anaerobic digestion is a biological process that takes place naturally when microorganisms break down organic matter in the absence of oxygen. In an enclosed chamber, controlled anaerobic digestion of organic matter produces biogas which is predominantly methane. The produced methane then can be directly used; or after certain conditioning, can be used in onsite power generation, heating homes or as vehicular fuel. Besides, organic waste is increasingly becoming a major problem in every society imposing serious economic and environmental concerns. For this reason, many contemporary researches are emphasizing in finding sustainable solutions to recycle and produce energy from such waste. In this context, this paper aims to investigate the potential of cow and chicken manure, and olive waste for biogas production obtained through the anaerobic digestion process.
 The substrates were placed in laboratory scale digesters without pretreatment. The retention time in the digesters was 30 days. The samples of the tested substrates were collected and analyzed for pH, total solids, ash, and the content of volatile solids (VS). Under mesophilic conditions, all combinations of cow and chicken manure, and olive waste with sludge by an anaerobic pond of a trickling filter treatment plant, as co-substrate, significantly improved biogas, and methane yields. The experimental results showed that chicken manure (CM) is the most suitable for anaerobic digestion (AD).
 The next step of the study will consist in implementing a large scale of biogas production plants and we will estimate the national potential of green energy produced by this technology and map the areas that need digesters.

Composition and Toxicity of Biogas Produced from Different Feedstocks in California.

Biogas is a renewable energy source composed of methane, carbon dioxide, and other trace compounds produced from anaerobic digestion of organic matter. A variety of feedstocks can be combined with different digestion techniques that each yields biogas with different trace compositions. California is expanding biogas production systems to help meet greenhouse gas reduction goals. Here, we report the composition of six California biogas streams from three different feedstocks (dairy manure, food waste, and municipal solid waste). The chemical and biological composition of raw biogas is reported, and the toxicity of combusted biogas is tested under fresh and photochemically aged conditions. Results show that municipal waste biogas contained elevated levels of chemicals associated with volatile chemical products such as aromatic hydrocarbons, siloxanes, and certain halogenated hydrocarbons. Food waste biogas contained elevated levels of sulfur-containing compounds including hydrogen sulfide, mercaptans, and sulfur dioxide. Biogas produced from dairy manure generally had lower concentrations of trace chemicals, but the combustion products had slightly higher toxicity response compared to the other feedstocks. Atmospheric aging performed in a photochemical smog chamber did not strongly change the toxicity (oxidative capacity or mutagenicity) of biogas combustion exhaust.

Theoretical and Experimental Results on the Recovery of Potato Processing Residuals by Anaerobic Digestion

Anaerobic digestion of organic matter with high moisture content has proven to be a suitable method for disposal of wet organic residuals with several advantages compared to other treatment technologies. This paper aimed at evaluating the theoretical and experimental biomethane potential of food processing residuals that are responsible for negative environmental impact, with exemplification for the potato processing waste. The biomethane potential is a useful parameter to assess the economic efficiency of anaerobic digestion processes as it can considerably influence the efficiency and the economic feasibility of the energy recovery technologies. Both experimental and theoretical biomethane potentials of potato waste in mesophilic anaerobic digestion as well as biodegradability of the substrate were estimated. Moreover, effects of microalgal extract addition on the digestion of potato waste were examined in an attempt to stimulate the anaerobic digestion. Cone model and a modified Gompertz model were used to predict the dynamics of biomethane production.

COD/sulfate ratio does not affect the methane yield and microbial diversity in anaerobic digesters

Anaerobic digestion of organic matter is the major route of biomethane production. However, in the presence of sulfate, sulfate-reducing bacteria (SRB) typically outcompete methanogens, which may reduce or even preclude methane production from sulfate-containing wastewaters. Although sulfate-reduction and methanogenesis can occur simultaneously, our limited understanding of the microbiology of anaerobic digesters treating sulfate-containing wastewaters constrains improvements in the production of methane from these systems. This study tested the effects of carbon sources and chemical oxygen demand-to-sulfate ratio (COD/SO42−) on the diversity and interactions of SRB and methanogens in an anaerobic digester treating a high-sulfate waste stream. Overall, the data showed that sulfate removal and methane generation occurred in varying efficiencies and the carbon source had limited effect on the methane yield. Importantly, the results demonstrated that methanogenic and SRB diversities were only affected by the carbon source and not by the COD/SO42− ratio.

Improvement in benthic habitat environment via granulated coal ash in a water body exposed to wastewater discharge

The discharge of untreated wastewater into a water body strongly deteriorates the benthic habitat environment of bottom sediment. In this study, field experiments were conducted in the Fukuyama inner harbor (Hiroshima, Japan), which is exposed to large amounts of untreated domestic wastewater discharge. The water quality in this harbor is seriously deteriorated during the summer season, resulting in an aggravation of the marine biological environment. This study examines the improvement in benthic habitat environment at the bottom of the harbor via the use of granulated coal ash (GCA, a by-product of coal-fired electric power plants). In the field experiments, the pore water quality and benthic habitat quality (i.e., the abundance and species richness) in GCA, gravel, and sediment layers were observed over time. The experiment results suggest that both GCA and gravel provide a better habitat environment for benthos compared to the sediment. In addition, the species richness in GCA was higher than that in gravel, suggesting that benthos can more easily survive in GCA than in gravels. It appears that the absorptive ability of GCA can remove the reductants released from the anaerobic digestion of organic matter and that the dissolution of the chemical components of GCA is significant factors in creating the higher species richness in the GCA layer.

Application of vadose-zone monitoring system for real-time characterization of leachate percolation in and under a municipal landfill

Leachates from solid-waste landfills are considered a severe threat to groundwater quality. The fate of pollutants in the waste and underlying unsaturated zone is crucial for evaluating environmental risks and selecting a restoration strategy. In this study, a vadose-zone monitoring system (VMS) installed in a municipal landfill was used, for the first time, to continuously track leachates percolation dynamics and assess their chemical transformation across the entire thickness of the waste body (15m) and underlying unsaturated zone (16m) to the water table. Winter rains were found to quickly infiltrate through the waste and underlying vadose zone despite a clay cover that was implemented as part of a restoration and leachate-prevention strategy. Within the waste body, the flow pattern was controlled by preferential flow paths, which changed frequently. It is hypothesized that ongoing decomposition of the waste creates dynamic variations in the waste’s physical structure and flow pattern. Water samples collected from the waste layer indicated the formation of highly polluted leachates. The chemical composition in the waste body showed extreme variability between sampling points with respect to DOC (407–31,464mg/L), BOD/COD ratios (0.07–0.55), Fe2+ (6.8–1154mg/L), ammonium (68–2924mg/L) and heavy metal concentrations. Environmental hot spots creating concentrated, aggressive, “acid-phase” leachates still exist in the waste more than 13years after closing the landfill. However, continuous changes in the flow pattern and moisture distribution affected the creation and decay of such environments. In the underlying sandy vadose zone, some sections repeatedly exhibited stronger and faster flow characteristics than others. These local fluxes of concentrated leachates rapidly transported heavy contaminant loads toward the groundwater. However results showed evidence of continual attenuation processes in the deep vadose zone, with the anaerobic digestion of organic matter, as well as the significant retention of heavy metals.

Modeling of Greenhouse Gas Emission from Livestock

The effects of climate change on humans and other living ecosystems is an area of on-going research. The ruminant livestock sector is considered to be one of the most significant contributors to the existing greenhouse gas (GHG) pool. However the there are opportunities to combat climate change by reducing the emission of GHGs from ruminants. Methane (CH4) and nitrous oxide (N2O) are emitted by ruminants via anaerobic digestion of organic matter in the rumen and manure, and by denitrification and nitrification processes which occur in manure. The quantification of these emissions by experimental methods is difficult and takes considerable time for analysis of the implications of the outputs from empirical studies, and for adaptation and mitigation strategies to be developed. To overcome these problems computer simulation models offer substantial scope for predicting GHG emissions. These models often include all farm activities while accurately predicting the GHG emissions including both direct as well as indirect sources. The models are fast and efficient in predicting emissions and provide valuable information on implementing the appropriate GHG mitigation strategies on farms. Further, these models help in testing the efficacy of various mitigation strategies that are employed to reduce GHG emissions. These models can be used to determine future adaptation and mitigation strategies, to reduce GHG emissions thereby combating livestock induced climate change.

Biodigesters: chemical, physical and biological factors related to their productivity

<p class="p1">Biodigesters are designed to optimize biogas production using organic wastes, thereby attaining clean, low-cost renewable energy. In 2008, a group of ITCR researchers worked on developing a wireless electronic system for control and protection of biogas production. One of the specific objectives of this work was to find information about methods to increase biogas production. In this review we established the mathematical parameters related to biogas estimation of productivity. We then focused on the influence of chemical factors such as substrate composition, substrate combinations, addition of fat, and presence of inhibitors. We also studied the effect of physical factors such as temperature, solids removal, protein exclusion and phase separation during anaerobic digestion of organic matter. Finally we attempted to determine the role of biological factors such as the addition of thermophilic bacteria and the importance of methanogens. </p>

Development of Mathematical Models and Application of the Modified Gompertz Model for Designing Batch Biogas Reactors

Biogas is a combustible gas produced by the anaerobic digestion of organic matter (biomass) in the absence of oxygen. In this study, mathematical models for the design of batch anaerobic biogas reactors for digesting cattle dungs at ambient temperatures (30 ± 3 °C) were developed. Biogas productions from five (5) reactors with varying mass of total solids were monitored for a period of 42 days. It was observed that optimal biogas yield (y t ) occurred at volatile solids concentration in the range of 60.0–80.0 g VS/L, which corresponds to 8.0–10.0 % total solids. Optimum biogas yield rates were between 1.44 and 1.64 ml/g VS/day. The modified Gompertz model was used in predicting maximum biogas yield (y m ), maximum biogas yield rate (R m ), the minimum time taken to produce biogas (λ), and these were found respectively to be between 68 and 86 ml/g VSloaded, 2.50–2.97 ml/g VSloaded/day and 9.7–12.0 days with goodness of fit ranging from 0.996 to 0.999. A relationship between maximum biogas yield potential and volatile substrate concentration was established to be ym = −0.0266[VS]2 + 4.8396[VS] + 129.1. An appropriate application of the developed models would lead to an optimal design of a biogas plant digesting cattle/livestock dungs with biogas and organic fertilizers production for farmers and gardeners alike.