Anaerobic bioconversion of municipal solid wastes

Applied Biochemistry and Biotechnology - The anaerobic bioconversion of municipal solid wastes (MSW) produces both a valuable fuel product (methane) and a residue useful as a soil amendment. The...     

Development of a novel laboratory scale high solids reactor for anaerobic digestion of processed municipal solid wastes for the production of methane

Economic evaluations of the capital costs for anaerobic digestion systems for gas production show that the reactor is a significant cost component. The successful application of high solids digestion of processed MSW (e.g., greater than 10% solids within the digester) would allow a decrease in reactor volume with maintenance of relatively high gas production rates. However, high solids slurries do not mix well in conventional stirred tank reactors. A horizontal shaft, hydraulically driven reactor was designed and fabricated to test the anaerobic digestion of high solids concentrations. Digester performance was evaluated as a function of experimental parameters such as nutrient requirements, feeding rates, pH control, and agitator design/ rotation speed; horsepower of mixing was also evaluated for the reactor. Several startup protocols were examined to obtain a biologically stable anaerobic fermentation at high solids levels.     

A Review on Current Status of Biochar Uses in Agriculture

In a time when climate change increases desertification and drought globally, novel and effective solutions are required in order to continue food production for the world’s increasing population. Synthetic fertilizers have been long used to improve the productivity of agricultural soils, part of which leaches into the environment and emits greenhouse gasses (GHG). Some fundamental challenges within agricultural practices include the improvement of water retention and microbiota in soils, as well as boosting the efficiency of fertilizers. Biochar is a nutrient rich material produced from biomass, gaining attention for soil amendment purposes, improving crop yields as well as for carbon sequestration. This study summarizes the potential benefits of biochar applications, placing emphasis on its application in the agricultural sector. It seems biochar used for soil amendment improves nutrient density of soils, water holding capacity, reduces fertilizer requirements, enhances soil microbiota, and increases crop yields. Additionally, biochar usage has many environmental benefits, economic benefits, and a potential role to play in carbon credit systems. Biochar (also known as biocarbon) may hold the answer to these fundamental requirements.     

Evaluation of Methanogenic Activity of Biogas Plant Slurry for Monitoring Codigestion of Ossein Factory Wastes and Cyanobacterial Biomass

Overall measurement of methanogenic activity of sludge and or slurry is thought as a key for understanding the basic physiology of anaerobic consortia involved in anaerobic digestion process of an alternative biomass. In this study, the methanogenic activity of biogas plant slurry was used to evaluate the anaerobic digestion of ossein factory wastes such as sinews and primary clarified bone waste (PCBW) and cyanobacterial biomass in standard assay conditions. A maximum methanogenic activity was reported here when ossein factory wastes mixed with cyanobacterial biomass in specific proportions in which sinews and PCBW alone also favored to a significant methane yield. Cyanobacterial biomass alone did not give a desirable methanogenic activity. Approximately 48% of total solids were destroyed from these wastes after 30 days. This study gives information on the use of these wastes with suitable proportions for taking an effort in a large-scale anaerobic digestion in an effective way of ossein factory.     

Anaerobic bioconversion of municipal solid wastes using a novel high-solids reactor design

Novel, laboratory-scale, high-solids reactors operated under mesophilic conditions were used to study the anaerobic fermentation of processed municipal solid waste (MSW) to methane. Product gas rate data were determined for organic loading rates ranging from 2.99–18.46 g of volatile solids (VS) per liter (L) per day (d). The data represent the anaerobic fermentation at high-solids levels within the reactor of 21–32%, while feeding a refuse-derived fuel (RDF)/MSW feedstock supplemented with a vitamin/mineral/nutrient solution. The average biogas yield was 0.59 L biogas/g VS added to the reactor system/d. The average methane composition of the biogas produced was 57.2%. The data indicate a linear relationship of increasing total biogas production with increasing organic loading rate to the process. The maximum organic loading rate obtainable with high-solids anaerobic digestion is in the range of 18–20 g VS/L·d to obtain 80% or greater bioconversion for the RDF/MSW feedstock. This loading rate is approximately four to six times greater than that which can be obtained with comparable low-solids anaerobic bioreactor technology.     

Pretreatment,Anaerobic Codigestion,or Both? Which Is More Suitable for the Enhancement of Methane Production from Agricultural Waste?

Pretreatment and codigestion are proven to be effective strategies for the enhancement of the anaerobic digestion of lignocellulosic residues. The purpose of this study is to evaluate the effects of pretreatment and codigestion on methane production and the hydrolysis rate in the anaerobic digestion of agricultural wastes (AWs). Thermal and different thermochemical pretreatments were applied on AWs. Sewage sludge (SS) was selected as a cosubstrate. Biochemical methane potential tests were performed by mixing SS with raw and pretreated AWs at different mixing ratios. Hydrolysis rates were estimated by the best fit obtained with the first-order kinetic model. As a result of the experimental and kinetic studies, the best strategy was determined to be thermochemical pretreatment with sodium hydroxide (NaOH). This strategy resulted in a maximum enhancement in the anaerobic digestion of AWs, a 56% increase in methane production, an 81.90% increase in the hydrolysis rate and a 79.63% decrease in the technical digestion time compared to raw AWs. On the other hand, anaerobic codigestion (AcoD) with SS was determined to be ineffective when it came to the enhancement of methane production and the hydrolysis rate. The most suitable mixing ratio was determined to be 80:20 (Aws/SS) for the AcoD of the studied AWs with SS in order to obtain the highest possible methane production without any antagonistic effect.     

Efficacy of hydrolytic enzyme augmentation and thermochemical pretreatments for increased secondary anaerobic digestion of treated municipal sewage sludges

Rising costs for landfill disposal of municipal sewage residues have prompted evaluation of alternative methods for reducing the bulk of the final waste. Representative samples of municipal sewage sludge residues were obtained from three major treatment plants in the United States, including Los Angeles (Hyperion), Denver (North Metro), and Chicago (Stickney). The majority of the treated, dewatered sewage sludge solids was found to be volatile (50–60%) and, presumably, biodegradable. Additionally, much of the volatile content was solubilized by both acid detergent fiber and neutral detergent fiber treatments, and was presumed to be proteineous microbial biomass in nature. Both low- and high-solids anaerobic digester systems, as well as the standard biochemical methane potential (BMP) assay, were utilized to evaluate the anaerobic digestibility of these sewage sludge residues. The low methane yields and, thus, the poor organic waste conversion indicated the need for treatment prior to bioconversion. The effectivenesss of various pretreatments based on assessment of increased soluble protein or organics and anaerobic digestibility as determined by the BMP assay was evaluated.     

Evaluation of Biogas Production Potential by Dry Anaerobic Digestion of Switchgrass–Animal Manure Mixtures

Anaerobic digestion is a biological method used to convert organic wastes into a stable product for land application with reduced environmental impacts. The biogas produced can be used as an alternative renewable energy source. Dry anaerobic digestion [>15% total solid (TS)] has an advantage over wet digestion (<10% TS) because it allows for the use of a smaller volume of reactor and because it reduces wastewater production. In addition, it produces a fertilizer that is easier to transport. Performance of anaerobic digestion of animal manure–switchgrass mixture was evaluated under dry (15% TS) and thermophilic conditions (55 °C). Three different mixtures of animal manure (swine, poultry, and dairy) and switchgrass were digested using batch-operated 1-L reactors. The swine manure test units showed 52.9% volatile solids (VS) removal during the 62-day trial, while dairy and poultry manure test units showed 9.3% and 20.2%, respectively. Over the 62 day digestion, the swine manure test units yielded the highest amount of methane 0.337 L CH₄ /g VS, while the dairy and poultry manure test units showed very poor methane yield 0.028 L CH₄/g VS and 0.002 L CH₄/g VS, respectively. Although dairy and poultry manure performed poorly, they may still have high potential as biomass for dry anaerobic digestion if appropriate designs are developed to prevent significant volatile fatty acid (VFA) accumulation and pH drop.     

Codigestion of proteinaceous industrial waste

Organic wastes are increasingly collected source separated, thus requiring additional treatment or recovery capacities for municipal biowastes, organic industrial wastes, as well as agroindustrial byproducts. In this study, we demonstrate that anaerobic digestion is preferentially suited for high-water-containing liquid or pasty waste materials. We also evaluate the suitability of various organic wastes and byproducts as substrates for anaerobic digestion and provide a current status survey of codigestion. Biodegradation tests and estimations of the biogas yield were carried out with semisolid and pasty proteins and lipids containing byproducts from slaughterhouses; pharmaceutical, food, and beverage industries; distilleries; and municipal biowastes. Biogas yields in batch tests ranged from 0.3 to 1.36 L/g of volatile solids_added. In continuous fermentation tests, hydraulic retention times (HRTs) between 12 and 60 d, at a fermentation temperature of 35°C, were required for stable operation and maximum gas yield. Laboratory experiments were scaled up to full-scale codigestion trials in municipal and agricultural digestion plants. Up to 30% cosubstrate addition was investigated, using municipal sewage sludge as well as cattle manure as basic substrate. Depending on addition rate and cosubstrate composition, the digester biogas productivity could be increased by 80–400%. About 5–15% cosubstrate addition proved to be best suited, without causing any detrimental effects on the digestion process or on the further use of the digestate.     

Thermal characterization of anaerobic sludges from wastewater treatments applied to biological generation of H<Subscript>2</Subscript>

A wide variety of organic residues may be used as energy source such as anaerobic sludge from wastewater treatment systems. However, due to inherent differences in composition, the proper characterization of these biomasses is essential to support their reuse through any conversion process. The aim of this study was the employment of thermal analysis techniques (TG/DTG and DTA) to perform the characterization of anaerobic sludges from different wastewater treatment plants (industrial and municipal), which were further applied for biological production of H₂. The different profiles observed through thermal characterization support the application of these residues as inocula, confirming their potential for H₂ production, while demonstrating the main causes for the different yields obtained (mol H₂ mol^?1 sucrose): 0.9 from sludge of brewery industry and 2.0 from sludge of municipal wastewater treatment plant, corresponding to the overall yields of 10.8 and 25%, respectively. These results confirm the versatility of thermal analysis techniques for biomass characterization, focused on its application for power generation. It is urgent to adopt more sustainable and cost-effective solutions for their management, considering a large amount of residues daily generated in both treatment processes addressed; therefore, biohydrogen production by anaerobic digestion may be a promising alternative for the reuse of both residues as it promotes their transformation from costly and potentially polluting waste into clean and renewable energy sources. The development of this anaerobic process is even more attractive in countries as Brazil, where the weather conditions are naturally favorable.     

A Review of the Anaerobic Digestion of Fruit and Vegetable Waste

Fruit and vegetable waste is an ever-growing global question. Anaerobic digestion techniques have been developed that facilitate turning such waste into possible sources for energy and fertilizer, simultaneously helping to reduce environmental pollution. However, various problems are encountered in applying these techniques. The purpose of this study is to review local and overseas studies, which focus on the use of anaerobic digestion to dispose fruit and vegetable wastes, discuss the acidification problems and solutions in applying anaerobic digestion for fruit and vegetable wastes and investigate the reactor design (comparing single phase with two phase) and the thermal pre-treatment for processing raw wastes. Furthermore, it analyses the dominant microorganisms involved at different stages of digestion and suggests a focus for future studies.     

Determination of imazaquin residues in soil by solid-phase extraction and high-performance liquid chromatography

A method has been developed for the quantitation of imazaquin residues in soil. The herbicide was extracted from soil with methanol-water (2 + 1, v/v) and cleaned up by strong anion-exchange solid-phase extraction cartridges. Analysis was performed by using high-performance liquid chromatography with ultraviolet detection. Average recoveries through the method ranged from 90.7 to 100.6%, with relative standard deviation equal to or lower than 6.6%. The limit of detection was estimated to be 0.0015 mg/kg, and the minimum quantitation concentration of imazaquin in soil was 0.005 mg/kg. This method was successfully applied to evaluate imazaquin residue levels in soil and its dissipation rates in a soybean field in the Xisanqi District of Beijing, People's Republic of China. The dissipation study showed that the half life of imazaquin in soil was 10.37 +/- 0.0135 days at 3 different application rates.     

苯醚甲环唑在芹菜及其土壤中的残留测定和消解动态研究

采用气相色谱-电子捕获检测, 对芹菜及其土壤中的苯醚甲环唑消解动态和最终残留量进行了研究, 评价了苯醚甲环唑在芹菜上使用后的残留行为和环境安全性. 苯醚甲环唑在芹菜及土壤中的残留消解动态均符合一级动力学方程, 苯醚甲环唑在芹菜上消解快; 苯醚甲环唑最终残留量与施药的剂量、施药次数及采样的间隔时间有关; 水解研究表明, 苯醚甲环唑是稳定的农药, 在不同温度和不同pH的研究条件下水解半衰期均大于166 d, 碱性条件更有利于苯醚甲环唑的降解.     

Horsepower requirements for high-solids anaerobic digestion

Applied Biochemistry and Biotechnology - Improved organic loading rates for anaerobic bioconversion of cellulosic feedstocks are possible through high-solids processing. Additionally, the reduction...     

Upgrading Solid Digestate from Anaerobic Digestion of Agricultural Waste as Performance Enhancer for Starch-Based Mulching Biofilm

Developing a green and sustainable method to upgrade biogas wastes into high value-added products is attracting more and more public attention. The application of solid residues as a performance enhancer in the manufacture of biofilms is a prospective way to replace conventional plastic based on fossil fuel. In this work, solid digestates from the anaerobic digestion of agricultural wastes, such as straw, cattle and chicken manures, were pretreated by an ultrasonic thermo-alkaline treatment to remove the nonfunctional compositions and then incorporated in plasticized starch paste to prepare mulching biofilms by the solution casting method. The results indicated that solid digestate particles dispersed homogenously in the starch matrix and gradually aggregated under the action of a hydrogen bond, leading to a transformation of the composites to a high crystalline structure. Consequently, the composite biofilm showed a higher tensile strength, elastic modulus, glass transition temperature and degradation temperature compared to the pure starch-based film. The light, water and GHG (greenhouse gas) barrier properties of the biofilm were also reinforced by the addition of solid digestates, performing well in sustaining the soil quality and minimizing N₂O or CH₄ emissions. As such, recycling solid digestates into a biodegradable plastic substitute not only creates a new business opportunity by producing high-performance biofilms but also reduces the environmental risk caused by biogas waste and plastics pollution.     

The effect of solid-liquid effluents from anaerobic digesters on soilmicrobial activity

A calorimetric procedure is developed to study the effect on the soil of the effluents resulting for the anaerobic digestion of slaughtering houses residues. DSC was used to study the pyrolysis properties of the effluent and the soil while isothermal calorimetry is applied to study the microbial activity in the effluent and to assess on its effect on the microbial activity of the soil where the industrial digester will be situated. The calorimetric data were studied together with the chemical and biological properties of that residue. Results showed that effluent is constituted by low levels of carbon and high levels of nitrogen. The power-time curves of the effluent have the typical shape of microbial growth yielding microbial growth rate constants between 0.37 and 0.53 h⁻¹ for about 4 and 11 h. The addition of the effluent to the soil decreases the heat of pyrolysis with time and stimulates the heat flow rate of the microbial metabolism.     

Evaluation of the Fate of Aldicarb and Its Metabolites in Oranges

Abstract

The accumulation, persistence and fate of systemic pesticide aldicarb was melencholy evaluated in orange crops. The concentration of this pesticide and its two toxic metabolites, aldicarb sulfoxide and aldicarb sulfone was determined in leaves, rind and pulp of three orange varieties (Satsuma, Navelina and Clemetina de Nules) and in the top soil of the orange groves. The groves were located in two different places in the Valencia Community (Spain). The analysis showed that the aldicarb concentration was lower than those of aldicarb sulfoxide and aldicarb sulfone. In all cases, the residues persisted at least 160 days in vegetable samples and between 157 and 227 days in soil samples. Residue concentrations measured in the soil samples were highly variable but a relation with the organic matter content can be observed. The residue levels found in vegetal products were higher in leaves than in rind, and in rind than in pulp. The maximum residue values were obtained between 47 and 70 days after the application. One hundred days after treatment (Security period) the residue levels of total fruit were lower than the maximum residue level of 0.2 mg/kg established by law.     

A sustainable approach for soil amendment; available plant nutrients in rice straws

The main aim of this study is to estimate the potential of mitigating the soil degradation by the utilization of rice straws, In every crop huge quantity of crop residue is generated along with the food grains. Only small part of the crop residue is used as cattle feed and other applications, significant quantity of these crop residues are either left unutilized or disposed by means of open field burning by the farmers, because other disposal options are not economically viable for the farmers. Consequences of open field burning of crop residues in India are, contribution of particulate matter in the atmosphere, emission of CO₂, CO, NH₃, NO_x, SO_x, and smog. On burning of crop residue heat produced is also accounted for the damage of microbes and other nutrients also present on the top layer of the soil, loss of organic carbon; it adversely affects soil fertility and productivity. It has a great economic potential as it contains high carbon content and significant amount of other essential plant nutrients which are required for plant growth. Sun dried rice straw samples were collected and analysed for primary nutrients (C, H, S, N, P₂O₅ and K₂O) required for plant growth. Moisture content was 11.70%, Elemental analysis of paddy straw on dry basis was found C = 36.04%, H = 5.25%, S = 0.28% & N = 0.69% P₂O₅ = 0.43% and K₂O = 0.64% in the kharif season 2021. These elements were quantified by using different advanced analytical techniques.     

High rates of nitrogen cycling in volcanic soils from Chilean grasslands

There are over one million hectares of pasture in Chile, and 80% and 50% of the country's milk and meat comes from 72% of this area, situated in the lake region of southern Chile. The soils are volcanic and a major characteristic is that they have very high organic matter (OM) contents with the potential to support plant growth with only moderate levels of added nitrogen (N). To understand better the potential fertility of these soils in order to maximise production and minimise losses of N, we undertook studies using the stable isotope of N ((15)N) to resolve the rates of the main internal N cycling processes in three soils representing the two main volcanic soil types: Osorno and Chiloé (Andisol) and Cudico (Ultisol). We also assessed the longer-term potential of these soils to sustain N release using anaerobic incubation. Gross rates (μg N g(-1) day(-1)) of mineralisation were 27.9, 27.1 and 15.5 and rates of immobilisation were 5.9, 12.0 and 6.3 for Osorno, Chiloé and Cudico, respectively, implying high rates of net mineralisation in these soils. This was confirmed by anaerobic incubation which gave potential seasonal net mineralisation indices of 1225, 1059 and 450 kg N ha(-1) in the top 10 cm soil layers of the three soils. However, plant production may still benefit from added N, as the release of N from organic sources may not be closely synchronised with crop demand. The low rates of nitrification that we found with these acidic soils suggest that the more mobile N (viz. nitrate-N) would be in limited supply and plants would have to compete for the less mobile ammonium-N with the soil microbial biomass. Nitrogen was mineralised in appreciable amounts even down to 60 cm depth, so that leaching could become significant, particularly if the soils were limed, which could enhance nitrification and N mobility through the soil profile.