Kazutaka Kuroda

Emissions of malodorous compounds and greenhouse gases from composting swine feces

Emissions of harmful gases, malodorous compounds and greenhouse gases emitted during composting of swine feces under continuous aeration were studied using a laboratory-scale composting apparatus. Concentrations of ammonia and sulfur compounds in the exhaust gas rose remarkably after starting and at every turning, and their changes reflected the odor concentrations calculated from sensory tests. Volatile fatty acids, in high concentrations at the start, were rapidly reduced within several hours from starting and did not rise again. Methane emission was observed within only 1 day from starting. Nitrous oxide repeatedly rose and fell after every turning, as did ammonia. From the viewpoint of nitrogen loss during composting, however, the total amount of nitrous oxide emission seemed quite small compared with that of ammonia.

Reducing nitrous oxide gas emissions from fill-and-draw type activated sludge process

Abstract To reduce nitrous oxide (N 2 O) emissions from fill-and-draw type activated sludge units treating swine wastewater, the N 2 O emission was compared between the continuous aeration process (conventional process) and the intermittent aeration process. About 35% of the influent nitrogen was emitted as N 2 O gas using the conventional process under 0.5 kg·m −3 ·d −1 BOD loading. About 60% of the N 2 O was emitted duing the first hours of aeration started just after daily charging. On the other hand, only less than 1% of the influent nitrogen was emitted as N 2 O gas during the intermittent aeration process.

Effects of struvite formation and nitratation promotion on nitrogenous emissions such as NH3, N2O and NO during swine manure composting.

To reduce nitrogenous emissions from composting, two different countermeasures were applied simultaneously in swine manure composting. One was forming struvite by adding Mg and P at the start of composting, and the other was to promote nitratation (nitrite being oxidized nitrate) by adding nitrite-oxidizing bacteria after the thermophilic phase of composting. In the laboratory- and mid-scale composting experiments, 25-43% of NH3, 52-80% of N2O and 96-99% of NO emissions were reduced. From the nitrogen balance, it was revealed that the struvite formation reduced not only NH3, but also other nitrogenous emissions except N2O. The amount of total nitrogen losses was reduced by 60% by the two combined countermeasures, against 51% by the struvite formation alone. However, the nitratation promotion dissolved struvite crystals due to the pH decline, diminishing the effect of struvite as a slow-release fertilizer.

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.