Composting of fibrous solids from cow manure and anaerobically digested manure

Fibrous solids mechanically separated from fresh cow manure (CMFM), thermophilically digested cow manure (TFM) and two-stage digested cow manure (TSFM) were composted for 7 weeks. The Volatile Solids content was reduced by 52%, 49% and 35% for CMFM, TFM and TSFM, respectively.The weekly Volatile Solids mass balance showed a temperature sensitivity above 60°C. Crude fiber analysis illustrated the initial differences between the materials and depicted the breakdown of the organic matter during composting. The matured materials were rich in lignin and ash relative to cellulose and hemicellulose concentrations. The end-product is intended for use as substitute growth media in plant nurseries.     

Composting of goat manure and wheat straw using pine cones as a bulking agent

This study aimed to determine the optimum mixture ratio of pine cones, goat manure and wheat straw and obtained optimal Free Air Space (FAS) values for composting. For this aim, pine cones were added at different ratios into goat manure and wheat straw mixtures. So, the FAS value of mixtures was fixed at four different levels. According to the results, the highest organic matter degradation and temperature value were obtained at the mixture ratio of 10% pine cones, 45% goat manure and 45% wheat straw. FAS value of this mixture was 32.8.     

Composting of poultry manure and wheat straw in a closed reactor: optimum mixture ratio and evolution of parameters

The main objectives of this work were to investigate the evolution of some principal physico-chemical properties (temperature, carbon dioxide, oxygen, ammonia, pH, electrical conductivity, organic matter) and microbial population (mesophilic and thermophilic bacteria and fungi) during composting poultry manure with wheat straw in a reactor system, and to evaluate the optimum mixture ratio for organic substrate production. The experiments were carried out in four small laboratory reactors (1 l) and one large reactor (32 l) under adiabatic conditions over 14 days. During the process the highest temperature was 64.6°C, pH varied between 7.40 and 8.85, electrical conductivity varied between 3.50 and 4.31 dS m⁻¹ and the highest value of organic matter (dry weight) degradation was 47.6%. Mesophilic bacteria and fungi predominated in the beginning, and started the degradation with generation of metabolic heat. By increasing the temperature in reactors, the number of thermophilic microorganisms also increased, which resulted in faster degradation of substrate. The application of a closed reactor showed a rapid degradation of manure/straw mixture as well as a good control of the emissions of air polluting gases into atmosphere. The results showed that the ratio of manure to straw 5.25:1 (dry weight) was better for composting process than the other mixture ratios.     

秸秆与牛粪混合发酵对秸秆降解及土壤肥力的影响

利用GET技术可以有效地降解秸秆生产清洁能源生物甲烷,达到无害化处理与利用秸秆的目的。本研究应用GET技术研究了发酵基质(秸秆∶牛粪)配比和温度对秸秆降解及土壤肥力的影响,以求为GET技术的推广与应用提供支撑。结果表明,各处理因素中发酵基质配比和温度及其相互作用对秸秆纤维素和半纤维素的降解有显著影响,两因数的交互作用对纤维素和半纤维素的降解也有显著作用,但对木质素的影响不显著。其中发酵基质配比以1∶1最为适宜,其纤维素和半纤维素的降解率分别为55. 39%和27. 75%;秸秆纤维素的降解率随着温度的升高而增加,但半纤维素降解率在30℃时达到最高,分别比10℃、20℃和40℃时高33. 80%、18. 37%和6. 26%。发酵基质配比和温度对厌氧发酵后土壤的肥力也有显著作用,土壤有机质、全氮和全磷含量均以1∶1配比处理和30℃处理条件下为最高。GET技术的应用还能显著改善土壤结构,厌氧发酵后土壤微团聚体粒径组成由小团聚体转化为大团聚体为主,土壤微团聚体分形维数显著下降。     

Cultivation of oyster mushrooms on wheat straw and bagasse substrate amended with distillery effluent

Summary Molasses-based distilleries produce large quantities of dark coloured effluent, which is a major cause of environmental pollution. An experiment was conducted to investigate the efficacy of distillery effluent amendment for edible mushroom production. Three species of oyster mushroom, namely Pleurotus florida Eger (EM 1303), Pleurotus pulmonarius (Fries) Quelet (EM 1302) and Pleurotus sajor-caju (Fries) Singer (EM 1304) were grown on wheat straw (variety UP 2338) and bagasse amended with post-anaerobic distillery effluent, a high organic load wastewater with high biochemical oxygen demand and chemical oxygen demand. Three different levels of effluent treatment were applied to bagasse and wheat straw. Wheat straw was found to be the preferred substrate and showed better results than bagasse in all treatments with respect to yield, biological efficiency (BE) and dry matter loss. P. florida (EM 1303) and P. pulmonarius (EM 1302) gave significantly enhanced yield with increasing levels of effluent, with BE reaching highest at 238.6% for P. florida (EM 1303). Using bagasse as a substrate, P. sajor-caju (EM 1304) and P.␣pulmonarius (EM 1302) exhibited a decreasing trend as compared to control. However, the effect of effluent concentrations did not influence yield and BE significantly in case of bagasse. The dry matter loss of the substrate varied from 9.4% to 53.4% in wheat straw and 17.5% to 45.2% in bagasse respectively.     

Characterization of microbial community structure during continuous anaerobic digestion of straw and cow manure

Responses of bacterial and archaeal communities to the addition of straw during anaerobic digestion of manure at different temperatures (37°C, 44°C and 52°C) were investigated using five laboratory-scale semi-continuous stirred tank reactors. The results revealed that including straw as co-substrate decreased the species richness for bacteria, whereas increasing the operating temperature decreased the species richness for both archaea and bacteria, and also the evenness of the bacteria. Taxonomic classifications of the archaeal community showed that Methanobrevibacter dominated in the manure samples, while Methanosarcina dominated in all digesters regardless of substrate. Increase of the operating temperature to 52°C led to increased relative abundance of Methanoculleus and Methanobacterium. Among the bacteria, the phyla Firmicutes and Bacteroidetes dominated within all samples. Compared with manure itself, digestion of manure resulted in a higher abundance of an uncultured class WWE1 and lower abundance of Bacilli. Adding straw to the digesters increased the level of Bacteroidia, while increasing the operating temperature decreased the level of this class and instead increased the relative abundance of an uncultured genus affiliated to order MBA08 (Clostridia). A considerable fraction of bacterial sequences could not be allocated to genus level, indicating that novel phylotypes are resident in these communities.     

Efficient conversion of wheat straw wastes into biohydrogen gas by cow dung compost

Efficient conversion of wheat straw wastes into biohydrogen gas by cow dung compost was reported for the first time. Batch tests were carried out to analyze influences of several environmental factors on biohydrogen production from wheat straw wastes. The performance of biohydrogen production using the raw wheat straw and HCl pretreated wheat straw was then compared in batch fermentation tests. The maximum cumulative hydrogen yield of 68.1 ml H2/g TVS was observed at 126.5 h, the value is about 136-fold as compared with that of raw wheat straw wastes. The maximum hydrogen production rate of 10.14 ml H2/g TVS h was obtained by a modified Gompertz equation. The hydrogen content in the biogas was 52.0% and there was no significant methane observed in this study. In addition, biodegradation characteristics of the substrate were also discussed. The experimental results showed that the pretreatment of the substrate plays a key role in the conversion of the wheat straw wastes into biohydrogen by the composts generating hydrogen.     

Composting of straw in small units

Summary Straw could be composted satisfactorily in 4 to 5 months in small concrete cells holding 30 lb. material (dry basis), providing the straw was thoroughly moistened and sufficient easily available nitrogeneous material added to give an initial carbon/nitrogen ratio of 40. During the composting process about half the dry matter was lost. Results were similar to those obtained using large cells holding 1500 lb. straw. Wire units holding 100 lb. straw were unsatisfactory. Changes in dry matter, carbon/nitrogen ratio, temperature, soluble inorganic nitrogen, and pH of composts prepared with various accelerators are reported.     

Characteristics of dairy manure composting with rice straw

The aim of this work was to investigate the effects of aeration rate, aeration method, moisture content, and manure age on the characteristics of dairy manure composting with rice straw in terms of composting temperature, oxygen consumption rate, emission of odorous gases, and final compost property. It was found that the aeration rate of 0.25 L/min-kg VS was capable of achieving the highest composting temperature, longest retention time of high temperature, and less emission of odor gases. Except for the composting temperature reached, there was no significant difference between bottom-forced and top-diffusion aerations in terms of final compost property. The higher initial moisture content (65%) was more favorable for its higher temperature, longer retention time of high temperature, and more stable end compost obtained. Fresh manure showed better composting performance than the aged manure for its higher temperature reached in less time and less ammonia emission. Oxygen consumption rates were basically similar to those of temperatures. Most emissions of the odorous gases occurred during the first week of composting, therefore, special attention should be paid to this period of time for effective odor control.     

Growth and survival of protozoa isolated from a tannery effluent

Industrial effluent from a tannery was used for the growth of algae in a medium containing various inorganic salts. Growth of algal cells became visible after 7 d. Two species of protozoa were observed to proliferate in the algal culture containing no organic supplement in the medium. The culture was kept bacteria-free by the use of antibiotics and was perpetuated for at least 150 d with no decline in the protozoan population. Efficient growth of protozoa in a culture of algae elucidated new modes of nutrition in protozoa. Cr(VI) was added to the medium to check the resistance of algae and protozoa against this heavy metal. Protozoa showed different degrees of resistance. The results indicate the importance of algae and protozoa in the process of bioremediation.     

Occurrence of chromium resistant thermotolerant coliforms in tannery effluent

Twenty six thermotolerant strains resistant to high levels of chromium (50-250 microg/ml) were isolated from treated tannery effluent. They were also found resistant to multiple heavy metals and antibiotics. Majority of them were resistant to copper and bacitracin. Nine strains representing different resistance patterns were selected for plasmid profile and conjugation studies. Agarose gel electrophoresis results revealed that 6 strains harboured a single plasmid, whereas 3 strains exhibited 2 plasmid bands. Among antimicrobials, co-trimazole and bacitracin and among metals, Cu2+, Cd2+, Zn2+ and Ni2+ resistance were transferred most frequently at variable rates. However, chromium resistance was transferred in 6 strains with a frequency ranging 19-49x10(-2). Resistance to Co2+ and Hg2+ did not transfer under environmental conditions. Among the nine strains, three were found predominantly uropathogenic Escherichia coli (UPEC) serotype 04, whereas two strains were untypable. In addition, 4 transconjugants also showed a positive result after serotyping.     

Evaluation of microbial population dynamics in the co-composting of cow manure and rice straw using high throughput sequencing analysis

Microbial population dynamics in co-composting of cow manure and rice straw were evaluated using 16S high throughput sequencing technology. Physicochemical factors, including temperature, pH, nitrogen contents, the ratio of carbon and nitrogen, and germination index, were also determined in this study. 16S high throughput sequencing results showed that bacterial community structure and composition significantly varied in each phase of composting. The major phyla included Bacteroidetes, Proteobacteria, Firmicutes, Actinobacteria and Planctomycetes, respectively. Bacteroidetes and Proteobacteria were the most abundant phyla in all phases, and Actinobacteria was just dominant in the mesophilic phase, while Firmicutes and Planctomycetes were ubiquitous. At the genus level, Simiduia, Flavobacterium, unclassified Chitinophagaceae and Flexibacter notably changed in each phase of composting. Bacterial community diversity in the mesophilic phase was higher than that in others based on the Shannon–Wiener index and Simpson diversity index. The ratio of carbon and nitrogen and germination index indicated that the co-composting of cow manure and rice straw reached maturation. The result of nitrogen contents showed that nitrogen loss mainly occurred in the thermophilic phase. In addition, the differences in the distributions of key OTUs between in the late thermophilic phase and the cooling and maturation phase were unobvious compared with other phase’s base on the principal component analysis. Redundancy analysis revealed that the changes of nitrogen played a predominant role in the distributions of OTUs during the composting process.     

Survival of Escherichia coli O157:H7 and Salmonella typhimurium in cow manure and cow manure slurry

An exponential linear destruction was observed for Escherichia coli O157:H7 and Salmonella typhimurium in cattle manure and manure slurry stored at 4, 20 or 37 degrees C. The resulting decimal reduction times ranged from 6 days to 3 weeks in manure and from 2 days to 5 weeks in manure slurry. The main effects of time as well as temperature were pronounced with the most rapid destruction at 37 degrees C. The ammonia concentration in manure increased slightly during storage but did not exceed 0.1%. pH values in the deeper layers of manure remained constant except at 37 degrees C when the pH increased by 1 unit in 60 days. In the surface layers of manure, pH increased by 1.5-2 units, the oxidation-reduction potential of the manure declined rapidly to values below -200 mV. These changes do not seem to be reflected in changing rates of bacterial destruction. The observed order of destruction makes it possible to predict storage conditions (temperature and time) that will lead to a predetermined level of reduction of the two pathogens.     

Bioconversion of wheat straw and wheat straw components into single-cell protein.

Several fungi (Aspergillus niger, A. terreus, Cochliobolus specifer, Myrothecium verrucaria, Rhizoctonia solani, Spicaria fusispora, Penicillium sp., and Gliocladium sp.) were isolated from decomposing wheat straw and tested for their ability to utilize whole straw and its components, holocellulose (hemicellulose and cellulose) and cellulose, for the production of single-cell protein (SCP). It was found that C. specifer was the most efficient fungus for protein synthesis with the three substrates. Using potassium nitrate as N source in mixtures of 0.04 g N/g substrate (0.04% wt./vol.) at pH 4.5, it was found that incubation periods of 3, 4, and 5 days were optimal for protein production on cellulose and holocellulose fractions, and whole straw, respectively. Whole native straw was found to be the most recalcitrant to bioconversion into SCP; however, protein production was almost doubled when the lignin component was removed using a mixture of sodium chlorite and acetic acid.     

Composting of rice straw with oilseed rape cake and poultry manure and its effects on faba bean (Vicia faba L.) growth and soil properties

Composting of rice straw with poultry manure and oilseed rape cake and its effects on growth and yield of faba bean and soil properties was studied in pot experiments at Gifu University, Japan in 2001/2002. The composts reached maturity in 90 days, were rich in organic matter and mineral nutrients, had a high level of stability, and no phytotoxicity. The addition of compost (20-200 g pot(-1)) improved selected soil chemical (increased total N, total C and CEC), physical (decreased particle density) and biological (increased soil respiration rate) properties. Application of composts at a rate of 20 g pot(-1) significantly increased growth, yield, yield components and total crude protein of faba bean plants. The benefit of this compost without chemical fertilizer demonstrated the validity and possibility of sustainable agronomic performance of faba bean using locally available recycled organic materials.     

Isolation of hexavalent chromium-reducing Cr-tolerant facultative anaerobes from tannery effluent

Several facultative anaerobes tolerant to high levels of chromate (>400 mg/ml) were isolated from tannery effluents. These isolates displayed varying degrees of Cr(VI) reduction under aerobic and anaerobic conditions at room temperature (24+/-2 degrees C). Interestingly, eight isolates were efficient in reducing 70% Cr(VI) anaerobically. This includes 5 isolates of genus Aerococcus, two isolates of Micrococcus and single isolate of genus Aeromonas. These isolates were subjected to further characterization for possible use in Cr(VI) detoxification of industrial wastes. This is the first report of Aerococcus sp. capable of Cr(VI) reduction >70% anaerobically. These bacteria were further checked for tolerance to a variety of other heavy metals. Our study indicates the possible use of these bacteria in environmental clean up.     

Detoxification and accumulation of chromium from tannery effluent and spent chrome effluent by Paecilomyces lilacinus fungi

The tannery industry process involves chromium (Cr) salts as a main constituent of the process. The Cr recovery is a part of the process where other salts are used to achieve separation and recovery for using Cr back in the process. The process steps may contain both forms of Cr [Cr(VI): hexavalent and Cr(III): trivalent]. The recovery of Cr from tannery industry effluent through biological systems is much needed. The diverse physicochemical characteristics of these effluents may limit the growth of microorganisms and hence the limitation towards possible practical application of microorganisms in real industrial effluent conditions. The present study attempted the ability of the Cr-resistant fungus Paecilomyces lilacinus [isolated through an enrichment culture technique at 25 000 mg l⁻¹ of Cr(III)] to grow and remove Cr [Cr(VI) and Cr(III)] from two physicochemically different undiluted tannery industry effluents (tannery effluent and spent chrome effluent) in the presence of cane sugar as a carbon source. Such attempts are made keeping in view the potential integration of biological processes in the overall Cr removal and recovery processes to improve its efficiency and environmental sustainability. The fungus has broad pH tolerance range and can reduce Cr(VI) both in acidic (pH 5.5) and alkaline (pH 8.0) conditions. The fungus showed the ability to remove Cr(VI) (1.24 mg l⁻¹) and total Cr (7.91 mg l⁻¹) from tannery effluent below the detection level within 18 h and 36 h of incubation, respectively, and ability to accumulate 189.13 mg Cr g⁻¹ of dry biomass within 600 h of incubation from spent chrome effluent [containing 3731.4 mg l⁻¹ of initial Cr(III) concentration].At 200 mg l⁻¹ of Cr(VI) in growth media, with 100% detoxification and with only 10.54% of total Cr accumulation in the biomass, P. lilacinus showed Cr(VI) reduction as a major mechanism of Cr(VI) detoxification. The time-course study revealed the log phase of the growth for the maximum specific reduction of Cr(VI) and stationary phase of the growth for its maximum specific accumulation of both the forms of Cr [Cr(III) and Cr(VI)] in its biomass. In growth media at 50 mg l⁻¹ and 200 mg l⁻¹ of Cr(VI), P. lilacinus showed 100% reduction within 36 h and 120 h of incubation, respectively. The high degree of positive correlation and statistically high degree of relationship (r² = 0.941) between the fungal growth and % Cr(VI) reduction by the fungus support the role of metabolically active cellular growth in Cr(VI) reduction by the fungus. Results indicate that expanded solid (sludge) retention times (SRTs) (stationary phase) can be recommended for the removal of Cr(III) through accumulation. In case of Cr(VI), reduction needs a priority; therefore, a non-expanded SRT is recommended for designing a continuous-flow completely stirred bioreactor so that a log phase of cellular growth can be maintained during the reduction process. This study reveals the strong potential of P. lilacinus fungi for the removal of Cr from tannery effluent and spent chrome effluent.     

Oyster mushroom cultivation with rice and wheat straw

Cultivation of the oyster mushroom, Pleurotus sajor-caju, on rice and wheat straw without nutrient supplementation was investigated. The effects of straw size reduction method and particle size, spawn inoculation level, and type of substrate (rice straw versus wheat straw) on mushroom yield, biological efficiency, bioconversion efficiency, and substrate degradation were determined. Two size reduction methods, grinding and chopping, were compared. The ground straw yielded higher mushroom growth rate and yield than the chopped straw. The growth cycles of mushrooms with the ground substrate were five days shorter than with the chopped straw for a similar particle size. However, it was found that when the straw was ground into particles that were too small, the mushroom yield decreased. With the three spawn levels tested (12%, 16% and 18%), the 12% level resulted in significantly lower mushroom yield than the other two levels. Comparing rice straw with wheat straw, rice straw yielded about 10% more mushrooms than wheat straw under the same cultivation conditions. The dry matter loss of the substrate after mushroom growth varied from 30.1% to 44.3%. The straw fiber remaining after fungal utilization was not as degradable as the original straw fiber, indicating that the fungal fermentation did not improve the feed value of the straw.     

Effects of pig manure and wheat straw on growth of mung bean seedlings grown in aluminium toxicity soil

Crop production in red soil areas may be limited by Al toxicity. A possible alternative to ameliorate Al toxicity is the application of such organic manure as crop straw and animal manure. A pot experiment was conducted to investigate the effects of organic materials on the alleviation of Al toxicity in acid red soil. Ground wheat straw, pig manure or CaCO3 were mixed with the soil and incubated, at 85% of water holding capacity and 25 degrees C, for 8 weeks. After the incubation, 14 seedlings of mung bean (Phaseolus aures Roxb) were allowed to grow for 12 days. Results showed that application of organic material or CaCO3 increased soil pH and decreased soil monomeric inorganic Al concentrations. Growth of mung bean seedling was improved sustantially by the application of organic material or CaCO3. Pig manure or wheat straw was more effective in ameliorating Al toxicity than was CaCO3. Mung bean plants receiving pig manure or wheat straw contained relatively high concentrations of P, Ca and K in their leaves. It is suggested that the beneficial effect of organic manure on mung bean is likely due to decreasing concentrations of monomeric inorganic Al concentrations in soil solution and improvement of mineral nutrition.