Animal Manure Research Articles

Crop Nutrition and Soil Fertility Management in Organic Potato Production Systems

Organic farming is a comprehensive production management system that fosters and improves the health of agroecosystems, encompassing biodiversity, biological cycles, and soil biological activity. The potato (Solanum tuberosum L.) is a crucial crop in organic farming systems, standing out as one of the most highly demanded organic products on the market. Among all crops, with potatoes, there is a very large yield gap between organic and conventional systems, attributable mainly to its intensive nutrient demands. The present review, considering the most relevant scientific literature worldwide, discusses the contemporary state of knowledge on crop nutrition and soil fertility management in organic potato crop production, analyzing the effects of animal manures, green manures, organic amendments, and biostimulants on organic potato tuber yield and quality. Overall, the main findings show a particular combination is needed to effectively maintain good soil fertility, satisfy the nutritional needs of the crop, and overcome the difference in potato yield between organic and conventional farming methods while meeting consumer demand. This combination entails using an animal manure or leguminous green manure with an organic soil amendment, and even better with a biofertilizer, such as a mycorrhizae-fungus-based one. It also emerged that more targeted studies are needed to select appropriate cultivars for organic potato farming systems to optimize this environmentally friendly production method.

Prevalence and antimicrobial susceptibility profile of Salmonella isolated from vegetable farms fertilized with animal manure in Addis Ababa Ethiopia

The resistance of foodborne pathogens to antimicrobial agents is a potential danger to human health. Hence, establishing the status of good agricultural practices (GAPs) and the antimicrobial susceptibility of major foodborne pathogens has a significant programmatic implication in planning interventions. The objective of this study was to assess the gap in attaining GAP and estimate the prevalence and antimicrobial susceptibility profile of Salmonella in vegetable farms fertilized with animal manure in Addis Ababa, Ethiopia. A total of 81 vegetable farms from four sub-cities in Addis Ababa were visited, and 1119 samples were collected: soil (n = 271), manure (n = 375), vegetables (n = 398), and dairy cattle feces (n = 75). Additional data were collected using a structured questionnaire. Isolation of Salmonella was done using standard microbiology techniques and antimicrobial susceptibility testing was conducted using disk diffusion assays. Carriage for antimicrobial resistance genes was tested using polymerase chain reaction (PCR). Among the 81 vegetable farms visited, 24.7% used animal manure without any treatment, 27.2% used properly stored animal manure and 80.2% were easily accessible to animals. The prevalence of Salmonella was 2.3% at the sample level, 17.3% at the vegetable farm level, and 2.5% in vegetables. The highest rate of resistance was recorded for streptomycin, 80.7% (21 of 26), followed by kanamycin, 65.4% (17 of 26), and gentamicin, 61.5% (16 of 26). Multidrug resistance was detected in 61.5% of the Salmonella isolates. Vegetable farms have a gap in attaining GAPs, which could contribute to increased contamination and the transfer of antimicrobial resistance to the vegetables. The application of GAPs, including proper preparation of compost and the appropriate use of antimicrobials in veterinary practices, are recommended to reduce the emergence and spread of antimicrobial resistance.

Exploring the antibiotic resistance genes removal dynamics in chicken manure by composting

Prolonged antibiotic usage in livestock farming leads to the accumulation of antibiotic resistance genes in animal manure. Composting has been shown as an effective way of removing antibiotic resistance from manures, but the specific mechanisms remain unclear. This study used time-series sampling and metagenomics to analyse the resistome types and their bacterial hosts in chicken manures. Composting significantly altered the physicochemical properties and microbiome composition, reduced antibiotic resistance genes by 65.71 %, mobile genetic elements by 68.15 % and horizontal gene transfer frequency. Source tracking revealed that Firmicutes, Actinobacteria, and Proteobacteria are the major bacterial hosts involved in the resistome and gene transfer events. Composting reduces the resistome risk by targeting pathogens such as Staphylococcus aureus. Structural equation modelling confirmed that composting reduces resistome risk by changing pH and pathogen abundance. This study demonstrates that composting is an effective strategy for mitigating resistome risk in chicken manure, thereby supporting the One Health initiative.

Influence of Chinese herbal plants on greenhouse gas emissions from pig manure composting and fermentation

To reduce greenhouse gas emissions during the composting of animal manure and promote the resource utilization of Chinese herbal plants, experiments on pig manure composting were conducted in a plastic greenhouse. A mixture of herbal powders (Radix isatidis and Radix Polygoni Multiflori, mixed in a 1:1 ratio) was added to the pig manure at concentrations of 0.05%, 0.1%, and 0.5% (w/w), respectively. The results showed that the emission peaks of greenhouse gases occurred in the early stages of composting. The addition of 0.5% of a mixture of Chinese herbal plant powders resulted in a significant reduction in cumulative emissions of CO2 (45.0%) and N2O (60.0%) compared to the control. This treatment also resulted in the lowest global warming potential, measured at 91.3 g kg−1, and significantly increased the germination index. The study concluded that adding 0.5% Chinese herbal plant powder to compost effectively mitigated greenhouse gas emissions during the composting process.

Environmental risks in swine biogas slurry-irrigated soils: A comprehensive analysis of antibiotic residues, resistome, and bacterial pathogens

Simple anaerobic digestion is insufficient to completely remove residual parent antibiotics and antibiotic resistance genes (ARGs) from animal manure. ARG prevalence in swine biogas slurry-irrigated soils threatens human health. However, comprehensive analysis of antibiotic residues, high-resolution resistance gene profiles, and pathogenic microbiomes in biogas slurry-irrigated soils is very limited. Here, we comprehensively determined the antibiotics, resistome, and potential pathogens distribution in these soils, using high-performance liquid chromatography-tandem mass spectrometry, high-throughput quantitative PCR, and 16S rRNA gene sequencing. The results revealed a significant enrichment of tetracyclines and fluoroquinolones antibiotics and ARGs in soils with prolonged biogas slurry irrigation, with a total of 12 antibiotics, 175 unique ARGs, and 9 mobile genetic elements (MGEs) detected. Quantification of veterinary antibiotic residues (especially chlortetracycline) showed significant correlations with multiple ARGs. The abundance of ARGs and MGEs was highest in the biogas slurry-irrigated soils, denoting a tight link between the application of biogas slurry and the spread of antibiotic resistance. The presence of 50 potential pathogenic bacterial genera, including 13 with multidrug resistance, was identified. Variation partitioning, combined with hierarchical partitioning analysis, indicated that Firmicutes, MGEs, and tetracyclines were the key drivers shaping the ARG profiles in biogas slurry-irrigated soils. The findings offer insights into the mechanisms of antibiotic residue and ARGs spread from the agricultural practice of biogas slurry irrigation, underscoring the necessity of sustainable soil management to mitigate the spread of antibiotic resistance.

Transformation of phosphorus speciation during hydrothermal treatment of digestate of rural animal manure

Digestate of rural animal manures (DM) contain valuable P resource, but when they are directly used on land, they can cause soil and water pollution. Hydrothermal treatment (HT) has been widely applied as an effective method of waste treatment and P recycling. This study aims to realize the P recovery in DM by illustrating the migration and transformation of phosphorus (P) species during HT process of DM. Two acids (e.g., hydrochloric acid and oxalic acid) were compared in terms of their abilities to extract P from solid products after HT process. The results revealed that organic phosphorus (OP) was converted into inorganic phosphorus (IP), whereas non-apatite phosphorus (NAIP, mainly AlPO4) was transformed to apatite phosphorus (AP, Ca3(PO4)2) during HT at different temperatures. Specifically, the percentage of IP increased from 30.4% in DDM to 90.6% after HT process at 220 °C (HT220). The P leaching efficiency of HT220 reached 94.8% during HCl extraction. The study indicated that P bioavailability and solubility could be improved by HT process. This study would provide deeper insights into the application of HT technology for recovery of P in DM, as well as provide guidance for P recovery and recycling from P containing wastes.

INTENSITY OF GREENHOUSE GAS FORMATION DUE TO LIVESTOCK FARMING ACTIVITIES – AS AN ENVIRONMENTAL FACTOR

According to numerous expert assessments by international organizations and specialists, animal husbandry makes a significant negative contribution to global climate change due to the emission of greenhouse gases (GHG), which are formed at different stages of livestock production as a result of various chemical and biological processes in the body of animals and in livestock waste. The domestic animal husbandry is developing mainly due to the intensification of production in the industry, but traditional farming methods as well as small-scale production in the individual sector also take place. Since the use of various technologies in animal husbandry has different effects on the level of environmental pollution and GHG emissions, the aim of the research was to study the differences in the intensity of GHG gas formation by one animal reared with individual features of animal rearing technologies and business activities. The intensity of gas formation and emission of CH4 and N2O in typical farms for pork production and milk production by one animal reared was determined, analyzed and substantiated. A significant variation in this indicator was found depending on the individual economic and technological features of the studied farms. The average weighted annual intensity of CH4 emission from animal manure in pig farms varied within the range of 0.95–25.71, in cattle farm – 2.74; CH4 from intestinal fermentation of dairy cows – 110.8–148.4; N2O (direct) in pig farms – 0.0–0.106, in cattle farm – 0.229; N2O (indirect) in pig farms – 0.071–0.097, in cattle farm – 0.174. The emission intensity is characterized separately in each age and sex group of animals in the herd structure of farms and the average weighted emission intensity in pork producing farms depending on the season. Based on the research results, it is proposed to use the generalized average annual indicator of greenhouse gas emissions per one average weighted animal reared (kg/head/year) as an indicator of the environmental load of livestock farms on the environment, which will allow planning production volumes with minimal environmental risks in the context of climate change.

Evaluations of Improved Forage Legume Potential for Pasture Land Improvement in Low Land and Mid Land Areas of East Shewa and West Arsi Zone

This study aims to evaluate the improved forage legume potential for pasture land improvement in low-land and mid-land areas of East Shewa and West Arsi zone of Oromia regional state during 2021/22 planting seasons. The natural pasture grazing land was selected to establish the experiment. The experiment was undertaken with RCBD design. The ripping was done before sowing and animal manures were applied before establishment to facilitate the germination of legumes forage. The experiment has four treatments with three replications including the control. The plot size was 4 m * 3 m and the distance between the plot and block were 1m and 1.5m respectively. The sample was taken by quadrant of 1 m * 1 m, weighed, and inserted into a paper bag. The sub-sample was taken for dry matter determination and biomass estimation. Laboratory chemical analyses for some of the major parameters have been done at ATARC. The feed sample was analyzed for dry matter (DM) and crude protein (PC) using AOAC (2000) method. The statistical analysis was undertaken by ANOVA procedures with Tukey's Studentized Range (HSD) Tests to separate the mean values for each parameter at P<0.05. Analysis of variance revealed that variations of sites and treatments had showed a significant effect at (P<0.05) on dry matter yield and ADL. In addition, the site effects had showed significant effects on leaf to steam ratio, percentage of dry matter, percentage of ash and coverages. The ANOVA result showed that there was no interactions effect (P<0.05) for all parameters. In addition, the dry matter have significance difference (P<0.05) between the treatments due to different legumes integration. The integrated siratro (T4) and desmodium (T3) have higher mean value of dry matter than the other treatments. Of the total dry matter, the Desmodium have 10.88% proportion while the Siratro have about 49.57%. In general, improved forage legumes integration result indicated that as to be appropriate option for natural pasture improvement in terms of quantity and quality. Thus, of the treatments the demodium and siratro components have higher dry matter and crude protein the T3 and T4 were recommended for natural pasture improvement in terms quantity and quality for lowland and midland agroecology.

Public Health Significance of Verocytotoxigenic Escherichia coli: An Overview

Meat is a global vital protein source catering to diverse diets. By 2050, world’s population may rise to 9 billion and the demand for meat will exceed supply, necessitating a doubling of meat production. Nutritionally rich composition makes meat, a fertile ground for numerous microbes, leading to spoilage and foodborne illnesses, impacting human health. External factors like poor hygiene, inadequate post-production storage, mishandling and more contribute to meat contamination. The zoonotic strains of E. coli can cause severe food poisoning, with over 700 identified serotypes, hence it is crucial to identify, monitor and control E. coli to ensure food safety. Among E. coli pathotypes, Verocytotoxigenic E. coli (VTEC) stands out as major cause of food poisoning. The VTEC toxin (Shiga toxin), can induce mild diarrhea to severe form of illness like Hemorrhagic Uremic Syndrome and Hemorrhagic Colitis, posing a severe public health risk. The Cattle is a primary reservoir for VTEC, which, by faecal shedding, can pollute food, water and the environment. Furthermore, E. coli can spread through contaminated meat, raw milk and milk products. This bacterium is commonly found in the immediate surroundings of animal reservoir, including soil, grass and manure, leading to potential contamination of milk. E. coli infections not only impact humans but also animals, with cattle, sheep and poultry acting as reservoirs for different E. coli strains. Cattle populations frequently harbor E. coli O157:H7 asymptomatic carriers, contributing to faecal contamination of food and water sources. Educating the public about the risks associated with improper meat handling and contamination is essential to reduce foodborne illnesses. Monitoring and surveillance of meat quality in local markets, as are crucial steps towards ensuring food safety. This underscores the importance of understanding and managing E. coli contamination in meat to safeguard public health and ensure the safety of meat products in the global food supply chain.

Size and polarity fractions of mobile organic matter from manure affect the sorption of sulfadiazine, caffeine and atenolol in soil

Waste-derived organics introduced to soils along with pharmaceutical active compounds (PhAC) are a crude mixture of compounds occurring in various size and polarity fractions. They affect the sorption of PhACs to soil; however, the relevant knowledge is still insufficient. The effects of different size and polarity fractions of manure-derived mobile organic matter (<63 µm) on the sorption of sulfadiazine, caffeine and atenolol to five topsoils were investigated. Mobilization of the PhACs was strongest in the presence of dissolved organic matter (mDOM, <0.45 µm), with a reduction of Kd of sulfadiazine, caffeine and atenolol by mean factors of 0.66, 0.57 and 0.41, respectively. The mobilizing effects of colloidal organic matter (0.45–10 µm) were slightly smaller. Fine particulate organic matter (10–63 µm) reduced the sorption of the PhACs in slightly acidic soils (pH 6.0), but increased it in strongly acidic soil (pH 4.3). Furthermore, hydrophobic (HO-mDOM) and hydrophilic (HI-mDOM) fractions of mDOM reduced the sorption capacity but increased the sorption nonlinearity of PhACs in soils. Effects of HO-mDOM and HI-mDOM were PhAC specific. It is suggested to consider the varying impacts of mobile fractions in animal manure and/or treated wastewater in evaluating the fate and environmental relevance of associated PhACs.

Effect of animal manure on population dynamics of indigenous soil Bacillus spp.

Effect of animal manure on population dynamics of indigenous soil Bacillus spp.

Integrating cover crops and organic amendments to mitigate the limitations of tillage on soil health and cotton productivity

AbstractVarious tillage systems have limitations on soil health, such as the degradation of soil structure and organic matter under conventional tillage (CT) systems, as well as short‐term soil compaction in conservation tillage systems. A 3‐year field experiment was established to evaluate the integration of cover crop (CC) and organic amendments (OAs) into CT and strip tillage (ST) systems, and their impact on soil properties and cotton (Gossypium hirsutum L.) productivity. The CC was cereal rye (Secale cereale), and the combined application of animal manure and biochar constituted the OA. In the third year, differences in soil compaction between the CT and ST systems were observed when the measurements were made after tillage. Moreover, integrating CC and OA under the CT and ST systems increased the soil depth to compaction zones. Soil compaction was observed at 27.5‐cm depth under CT, at 30‐cm depth under CT integrated with CC and OA, at 10‐cm depth under ST, and at 15‐cm depth under ST integrated with CC and OA, using 2 MPa as the threshold. In general, the integration of CC and OA tended to increase soil respiration, organic matter, and available nutrients, but the effects were not consistent across years and soil depth. Despite differences in the various soil health properties, the management systems had minimum impact on cotton productivity and fiber quality, indicating the ST was effective in preparing the seedbed. Moreover, the differences in soil properties were not at yield‐limiting levels within 3 years of the study.

Influence of Hydrothermal Carbonization (HTC) Temperature on Hydrochar and Process Liquid for Poultry, Swine, and Dairy Manure

Hydrothermal carbonization (HTC) is a promising technology for wet manure treatment by converting animal manure into valuable fuels, materials, and chemicals. Among other HTC process parameters, the temperature influences HTC products the most. As various animal manures have different compositions, it is not certain how the HTC temperature influences the hydrochar and HTC process liquid. To evaluate the temperature’s effect on HTC, three different manures (poultry, swine, and dairy) were hydrothermally carbonized at three different temperatures (180, 220, and 260 °C), and solid and liquid products were characterized for their morphology, elemental compositions, and ions. The carbon contents of the hydrochar reached as high as 38.98 ± 0.36% and 40.05 ± 0.57% for poultry and swine manure, respectively, when these manures were treated at 260 °C. Ammonium showed an around 30% increase in poultry manure hydrochar with the increase in the HTC temperature. In contrast, in swine manure, it decreased by around 80%, and in dairy manure, the HTC temperature did not have any remarkable effect on the ammonium content. The process liquids from HTC of dairy manure at 220 °C showed the most balanced distribution of different ions, with 4970 ± 673 ppm of sodium, 4354 ± 437 ppm of ammonium, 2766 ± 417 ppm of potassium, 978 ± 82 ppm of magnesium, 953 ± 143 ppm of calcium, 3607 ± 16 ppm of chloride, and 39 ± 7 ppm of phosphate. These results emphasize the manure-specific effects of the HTC temperature on both solid and liquid products, indicating the need for optimized strategies to enhance HTC processes for various types of animal manures.

Combined use of digestate and inorganic fertilizer alleviates the burden of class 1 integrons in perennial ryegrass rhizosphere without compromising aerial biomass production.

Antimicrobial resistance (AMR) is one of the main global health challenges. Anaerobic digestion (AD) can significantly reduce the burden of antibiotic resistance genes (ARGs) in animal manures. However, the reduction is often incomplete. The agronomic use of digestates requires assessments of their effects on soil ARGs. The objective of this study was to assess the effect of digestate on the abundance of ARGs and mobile genetic elements (MGEs) in the rhizosphere of ryegrass (Lolium perenne L.) and to determine whether half-dose replacement of digestate with urea (combined fertilizer) can be implemented as a safer approach while maintaining a similar biomass production. A greenhouse assay was conducted during 190days under a completely randomized design with two experimental factors: fertilizer type (unfertilized control and fertilized treatments with equal N dose: digestate, urea and combined fertilizer) and sampling date (16 and 148days after the last application). The results indicated that the digestate significantly increased the abundance of clinical class 1 integrons (intI1 gene) relative to the unfertilized control at both sampling dates (P < 0.05), while the combined fertilizer only increased them at the first sampling. Sixteen days after completing the fertilization scheme only the combined fertilizer and urea significantly increased the biomass production relative to the control (P < 0.05). Additionally, by the end of the assay, the combined fertilizer showed significantly lower levels of the macrolide-resistance gene ermB than digestate and a cumulative biomass similar to urea or digestate. Overall, the combined fertilizer can alleviate the burden of integrons and ermB while simultaneously improving biomass production.

Effect of Organic Manure on Sorghum (Sorghum bicolor) Yield, Runoff and Soil Loss at Tahitay-Adiabo District, Tigray, Ethiopia

A field experiment was carried out in Tahitay Adiabo district, Tigray, Ethiopia to study the impact of organic manure on soil erosion, runoff, and sorghum yield during the cropping seasons of 2019 and 2020. The experiment utilized a randomized complete block design (RCBD) with tri replicates. The treatments included control, compost, animal manure, compost with mulch, animal manure with mulch, and recommended NP fertilizer. Each plot measured 6m x 4m and was situated on a 4% sloped terrain. The findings indicated significant differences (P&lt;0.01) among the treatments in terms of their influence on runoff volume, soil erosion, and sorghum yield. The application of compost with mulch and animal manure with mulch was particularly effective in reducing soil erosion and runoff compared to treatments using inorganic fertilizer and manure without mulch. Moreover, the control, animal manure, and inorganic fertilizer (NP-fertilizer) treatments exhibited high levels of soil loss and runoff volume, highlighting the effectiveness of compost with mulch and animal manure with mulch in mitigating soil erosion and runoff under the prevailing slope and rainfall conditions of the study area.

Renewable energy sources in Kyrgyzstan and energy supply to rural consumers

The study assesses the potential of renewable energy sources in Kyrgyzstan and explores their application to provide energy to rural consumers. This study used an approximation of the parabolic function of solar radiation change, statistical processing of data on the average annual water flow of small rivers, as well as calculation of the volume of manure produced and its processing into biogas and bio fertilisers to assess their potential in agriculture and environmental impact. Kyrgyzstan, located between 40 and 68° north latitude, has evenly distributed solar radiation, small rivers and biomass, which have significant renewable resources. The distribution of solar radiation on the territory corresponds to the normal law of the monthly average mathematical expectation of 175.79 kWh/(m²*month) and a standard deviation of 92.44 kWh/(m²*month). On average, each square metre of a solar power plant can produce 0.451 kWh of energy. The intervals of average water discharge between the small rivers of Kyrgyzstan follow a power law distribution with a mathematical expectation of 3.112 m³/s and a standard deviation of 2.46 m³/s. With a natural water flow rate of 0.652 m³/s, a low-pressure micro-hydroelectric power plant (with a water head of 1 to 2 m) can generate up to 8.95 kW of power. The total consumption of biogas by an average farm in Kyrgyzstan and its consumption for heating raw materials in a bioreactor during the cold season ranges from 16.34 to 18.93 kg/hour. This demand for biogas is met by producing domestic feedstock (animal manure) using compact biogas plants with reactors of up to 20 m³. These facts indicate that the use of the above-mentioned renewable energy sources in Kyrgyzstan can provide autonomous power supply to remote rural consumers and contribute to solving existing environmental problems, as well as energy-saving

A Review of Biogas Production from Small-Scale Anaerobic Digestion Plants

One of the most serious problems facing the whole world today is global warming. Their lease of greenhouse gases is exacerbating the effects of global warming. Reduced greenhouse gas emissions and searching for alternative energy sources are becoming increasingly crucial. This study aims to review that one of the effective methods for lowering greenhouse gas emissions is the creation of biogas from agricultural waste using anaerobic digester plants. A lab-scale 5-liter batch fermenter was incubated at room temperature, specifically mesophilic (35°C). Biogas is a clean, reasonably priced, and sustainable energy source produced by the anaerobic fermentation of waste and organic waste. Mixing sludge and waste to react with each other during biogas production is essential. Factors affecting biogas, such as loading rate, retention time, operating ambient temperature, pH, mixing, etc., are also discussed. Asia is a region where the generation of this form of renewable energy is widespread, particularly in nations like China and India. The generation of biogas never has any adverse environmental effects, but it also yields environmentally safe byproducts. Agricultural waste is a large and anthropogenic source of methane in the atmosphere. It can be converted into nutrient-rich fertilizer. Agricultural waste, food waste, animal or human manure, and other organic waste are all converted into energy (in the form of biogas or electricity) using anaerobic digesters. Another advantage of biological fermentation is that it leaves behind a high-quality organic fertilizer

The resistome of the food chain: A One Health perspective.

Antimicrobial resistance (AMR) represents a significant global health problem which challenges Sustainable Development Goal 3 of the United Nations, with growing concerns about the possibility of AMR transmission through the food chain. The indiscriminate use of antimicrobials for the treatment of food production animals and for agricultural crop improvement, in addition to the direct discharge of livestock farm residues to sewage and the use of animal manure in agriculture, are among the factors that can facilitate the selection and transmission of AMR throughout the food chain. The study of food microbiomes has been boosted by the advent of next-generation sequencing techniques, which have enabled gaining in-depth understanding of the diversity of antimicrobial resistance genes present in food and associated environments (the so-called resistome). The aim of this review is to provide an accurate and comprehensive overview of the knowledge currently available on the resistome of the most frequently consumed foods worldwide, from a One Health perspective. To this end, the different metagenomic studies which have been conducted to characterize the resistome of foods are compiled and critically discussed.

The effect of raw material (cow and chicken manure) and reactor type for improving and maximizing biogas production.

Biomass energy is a type of renewable energy and animal waste is one of the main resources for its production. The purpose of this study is to investigate the effect of raw material type (cow and chicken manure) and the type of reactor (digester) on the biogas produced by measuring the amount of methane in the product. Three types of digester (metal, simple PVC, and PVC with leachate rotation) with the same volume (10 L) were prepared. Equipment was installed on the digesters to measure the pH and volume of produced gas. The experiments were carried out in controlled temperature conditions (28-30 °C) and in two stages. The first experiment was to load the digesters with cow excrement, and the second experiment was to load the digesters with chicken excrement. In both experiments, the digesters were fed with 1.5 kg of animal manure and water with a ratio of 1:1. During a period of 60 days, the volume of biogas and methane produced was measured and recorded. The results showed that the amount of biogas produced from chicken waste is more than the amount obtained from cow waste. However, the amount of methane produced using cow excrement was more than that of chicken excrement. Also, the performance of PVC digester with leachate rotation was better than the other two digesters, which could be due to the mixing of raw materials in this type of digester.

Bioconversion of organic wastes: treatment sludges, animal manures, and agricultural wastes

AbstractThis study aimed to investigate the compostability of treatment sludge and to determine the effects of adding different animal manures (cattle, pig, horse, and chicken) and agricultural waste (sunflower stalks) on the composting process. Five different compost reactors (M1, M2, M3, M4, and M5) were operated. Sunflower stalks were added to all reactors as a bulking agent at the rate of 20%. Treatment sludge (80%) and bulking agent were added to the M1 reactor, where animal manure was not added, while 40% treatment sludge and 40% animal manure were added to the other reactors. In the reactors where animal manure was added, cattle (M2), pig (M3), horse (M4), and chicken (M5) manure were used, respectively. The temperature, pH, electrical conductivity, organic matter (OM), carbon to nitrogen ratio (C/N), total Kjeldahl nitrogen, and total phosphorus were monitored during the 21-day process. The highest OM loss (64.8%) occurred in the M2 reactor, and the maximum temperature (62.7 °C) was achieved. The high temperatures reached in the reactor increased microbial activity, resulting in rapid decomposition of OM and elimination of pathogens. With a maximum reduction in the C/N ratio (40%), carbon and nitrogen balance was achieved, thus obtaining a more stable and higher quality compost for plants in this reactor. In the M1 reactor, where only treatment sludge was composted, lower microbiological activity occurred compared to the other mixtures due to the lack of substrate. It can be said that composting treatment sludge together with animal manures will provide higher quality end products.