Dai Hanajima

Characterization and spatial distribution of bacterial communities within passively aerated cattle manure composting piles

The bacterial communities in the core, bottom, top, middle-surface, and lower-surface full-scale passively aerated cattle manure compost was investigated using DGGE of PCR-amplified 16S rRNA sequences. Some Bacillus species and strictly anaerobic thermophilic Clostridium species were dominant only in the core and bottom zones. In contrast, bands belonging to mesophilic bacteria such as Bacteroidetes, Clostoridia,alpha and gamma-proteobacteria were detected in surface zones, even in the initial thermophilic stage of the process. Our results clearly show the spatial distribution of the microbial community within full-scale composting piles, which indicates N or C conversion by zone-specific bacterial communities were occurring in each zone of the pile.

Isolation of Thermophilic Ammonium-tolerant Bacterium and Its Application to Reduce Ammonia Emission during Composting of Animal Wastes

A thermophilic bacterium, strain TAT105, was isolated from compost made of animal wastes. TAT105 had high tolerance to ammonium nitrogen up to 1200 mM, and highly assimilated nitrogen during the growth on swine feces. The strain was classified into Bacillus, close to Bacillus pallidus. To evaluate the effect of adding TAT105 to ammonia (NH3) emission during the composting process of animal wastes, laboratory scale composting was done. NH3 emission tended to be lower and nitrogen loss was smaller in the TAT105-added material than in the control material to which TAT105 was not added. Thermophilic ammonium-tolerant bacteria in the TAT105-added material increased to about 8×109 CFU/g of dry matter on the average during the tests, and most of them were judged to be TAT105 from morphological colony discrimination. These results suggested the possibility of reducing NH3 emission from composting of animal wastes by adding TAT105.

Evaluation of full-scale biofilter with rockwool mixture treating ammonia gas from livestock manure composting.

NH3 removal by a full-scale biofilter with rockwool packing materials was studied by measuring the gases and potential nitrification and denitrification activities of those materials in order to improve the biofiltration technology used in livestock farms. The rockwool biofilter was a durable and effective system for removing NH3, which was varied with the turning of manure composts. Furthermore, NH3 could be treated in the absence of an extra increase in two greenhouse gases, N2O and CH4. Potential nitrification and denitrification activities of the packing materials were estimated to be 8.2-12.2 mg N, and 1.42-4.69 mg N/100 g dry samples per day, respectively. The results suggested that potential nitrification and denitrification activities would increase within the biofilter where substrates, NH3 or NO3(-), have accumulated as a result of its operation. However, since percolate water contained high concentrations of NH4(+) and NO3(-), further improvement is required by reducing nitrogenous compounds within both the biofilter and percolate water.

Key odor components responsible for the impact on olfactory sense during swine feces composting

This study aimed to identify the major odor contributing components produced during swine feces composting which have an impact on the olfactory senses. A total of 64 gas samples collected at different stages of composting were analyzed by both a gas chromatograph and human panel test using the triangle odor bag method. Multiple regression analysis of representative odor substances present in the outlet gas was carried out employing the odor index (OI) as the dependent variable and the odor unit as the independent variable. The recorded changes in OI indicated that turning was an important event during odor evolution, and that the odor emission during the thermophilic phase should be the main target for odor abatement. The model incorporating ammonia, methyl mercaptan and dimethyl sulfide as independent variables confirmed the value of the OI (R(2)=0.70). These compounds were identified to be the key odor components significantly determining the OI.

The impact of using mature compost on nitrous oxide emission and the denitrifier community in the cattle manure composting process.

The diversity and dynamics of the denitrifying genes (nirS, nirK, and nosZ) encoding nitrite reductase and nitrous oxide (N2O) reductase in the dairy cattle manure composting process were investigated. A mixture of dried grass with a cattle manure compost pile and a mature compost-added pile were used, and denaturing gradient gel electrophoresis was used for denitrifier community analysis. The diversity of nirK and nosZ genes significantly changed in the initial stage of composting. These variations might have been induced by the high temperature. The diversity of nirK was constant after the initial variation. On the other hand, the diversity of nosZ changed in the latter half of the process, a change which might have been induced by the accumulation of nitrate and nitrite. The nirS gene fragments could not be detected. The use of mature compost that contains nitrate and nitrite promoted the N2O emission and significantly affected the variation of nosZ diversity in the initial stage of composting, but did not affect the variation of nirK diversity. Many Pseudomonas-like nirK and nosZ gene fragments were detected in the stage in which N2O was actively emitted.

Nitrogen removal by co-occurring methane oxidation, denitrification, aerobic ammonium oxidation, and anammox

The pathway for removing NO3− and NH4+ from wastewater in the presence of both CH4 and O2 was clarified by studying microbial activity and community. Batch incubation tests were performed to characterize the microbial activity of the sludge, which was acclimatized in a bioreactor in which O2 and CH4 were supplied to treat wastewater containing NO3− and NH4+. The tests showed that the sludge removed significant amounts of NO3− and NH4+ in the presence of CH4 and O2, and the presence of the activity of methane oxidation, denitrification, nitrification, and anammox in the sludge. It was estimated that the total inorganic nitrogen removal was attributed to denitrification associated with methane oxidation as 53.4%, microbial assimilation as 37.9%, and anammox as 8.7%. Nitrification also contributed to NH4+ decrease as 34.5% and anammox as 6.4%. Anammox activity was unambiguously demonstrated by 29N2 production in anaerobic batch incubation with 15N-labeled inorganic nitrogen compounds. The presence of methane-oxidizing bacteria and candidate denitrifiers in the sludge was shown by denaturing gradient gel electrophoresis of 16S rRNA gene fragments. Clone library analysis of the PCR-amplified 16S rRNA gene fragment using specific primers for aerobic ammonium oxidizer and anammox revealed the presence of these bacteria. The results reveal that complex nitrogen-removal processes occur in the presence of CH4 and O2 by methanotroph, denitrifier, aerobic ammonium oxidizer, and anammox.

Enhancement of the thermophilic stage in cattle waste composting by addition of tofu residue

The microbial degradation and temperature rise during the composting of a cattle waste and rice straw mixture blended with tofu (soybean curd) residue was investigated using an insulated and unheated in-vessel composter (effective volume, 12 1) and a static pile with passive aeration. The addition of 11% (dry weight basis) of tofu residue shortened the time required for temperature to reach the thermophilic phase and increased the duration of the temperatures above 55 degrees C significantly, but the maximum temperature was not affected by the additive level. As shown by the change in BOD, most of the easily biodegradable matter in the tofu residue was consumed during 12 days of composting. The same results were observed in the temperature profile of the static pile with passive aeration. Tofu residue addition yielded a higher maximum temperature and a nearly two times longer duration of temperatures above 55 degrees C in almost all locations of the pile. The use of tofu residue as a co-composting material would promote thermophilic degradation throughout the entire composting mass.

Bacterial community dynamics in aerated cow manure slurry at different aeration intensities

Aims:  This study aimed to characterize microbial community dynamics in aerated cow manure slurry at different aeration intensities.

Responses of community structure of amoA-encoding archaea and ammonia-oxidizing bacteria in ammonia biofilter with rockwool mixtures to the gradual increases in ammonium and nitrate

To investigate community shifts of amoA‐encoding archaea (AEA) and ammonia‐oxidizing bacteria (AOB) in biofilter under nitrogen accumulation process.

Comparison of the composting process using ear corn residue and three other conventional bulking agents during cow manure composting under high-moisture conditions

To elucidate the characteristics of ear corn residue as a bulking agent, the composting process using this residue was compared with processes using three other conventional materials such as sawdust, wheat straw and rice husk, employing a bench-scale composting reactor. As evaluated via biochemical oxygen demand (BOD), ear corn residue contains 3.3 and 2.0 times more easily digestible materials than sawdust and rice husk, respectively. In addition, mixing ear corn residue with manure resulted in reduced bulk density, which was the same as that of wheat straw and was 0.58 and 0.67 times lower than that of sawdust and a rice husk mixture, respectively. To evaluate temperature generation during the composting process, the maximum temperature and area under the temperature curve (AUCTEMP) were compared among the mixed composts of four bulking agents. Maximum temperature (54.3°C) as well as AUCTEMP (7310°C●h) of ear corn residue were significantly higher than those of sawdust and rice husk (P<0.05), and they are similar to that of wheat straw mixed compost. Along with the value of AUCTEMP, the highest organic matter losses of 31.1% were observed in ear corn residue mixed compost, followed by wheat straw, saw dust and rice husk.