The effects of MgCl₂ addition to composting material on struvite precipitation and ammonia emission were investigated. Beef cattle manure was used as the composting material and the 15-day composting process was carried out in a small-size reactor. When the rate of MgCl₂ addition was increased, the pH of the initial material decreased and the electrical conductivity increased. In addition, the degradation rate of volatile matter decreased to 63 % of that without addition of MgCl₂ when the addition rate was 0.4 mole per kg of initial dry manure (mol kg_DM0^-1). An increase in struvite nitrogen was observed after MgCl₂ addition at 0.03 mol kg_DM0^-1 (MgCl₂ additon: 0.1 mol kg_DM0^-1) ~0.07 (MgCl₂ additon: 0.4 mol kg_DM0^-1), and the utilization rate of Mg from additional MgCl₂ for struvite precipitation was calculated to be 34-16 %. Ammonia emission after 0.4 mol kg_DM0^-1 MgCl₂ addition decreased to 70 % of that without MgCl₂ addition. These results suggest that, following the addition of MgCl₂ to composting material pH reduction had a greater effect on the reduction of ammonia emission than did the increase in struvite precipitation.

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The internal pressure coefficient of a pipe-framed greenhouse is numerically simulated by using the time history of external pressures measured at the locations of gaps existing in the walls of pipe-framed greenhouse in a turbulent boundary layer with a 1:40 scale model. The external pressures are also measured at two cross-sections providing the largest load effects on the structural frame and cladding. Focus is on the bending moment at the windward column base of a frame placed at about 1.0H inside from the gable wall, with H being the model height, for discussing the design wind loads on structural frames. Based on the results, we proposed models of the internal pressure coefficient and the peak internal pressure coefficient to be combined with those of the external pressure coefficient and the peak external pressure coefficient for designing the structural frames and cladding, respectively, which we had proposed in our previous studies. A good agreement of the load effects predicted by these models with those obtained from a time history analysis indicates that the proposed models of the external and internal pressure coefficients are reasonable.

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Lately, the use of air source heat pumps in a greenhouse has attracted attention. COP (Coefficient of performance) is used as an indicator of the performance of the heat pump. Since the environmental condition regulated by JIS standards and that in a greenhouse to measure COP are very different, measurement of COP in the greenhouse has been requested. In this study, we measured COP using an air enthalpy method with the heat pump installed in a greenhouse. First, the air temperature and the wind speed of the heat pump outlet which influence the COP were measured. The wind speed at the left of the outlet was 2.7 m/sec faster than that at the center. In contrast, air temperature at the left was 2.5 ℃ lower than that at the center. Second, we developed a measuring device for COP which consisted of a duct, a hood air collector, a suction fan controlled with an inverter and a Pitot tube to avoid variation of wind speed and temperature. The variation of the air temperature was reduced within 0.3 ℃ and the difference of air volume between the data provided by the manufacturer and the value obtained by the device was less than 5 %. Finally, the device was tested under the similar condition of JIS standards and in the greenhouse, demonstrating that the device is effective in measuring COP accurately

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In response to the Fukushima Dai-ichi nuclear disaster, radioactivity tests are being done on all brown rice grown in Fukushima Prefecture under the instruction of the Fukushima Prefectural government. Test results have shown that only a few bags of brown rice harvested in 2012 contained radioactive cesium which exceeds regulation levels (100 Bq/kg). As a result of these findings, both the Japanese Ministry of Agriculture, Forestry and Fisheries and the Fukushima Prefectural government suspected that the rice was not contaminated during growth but during processing by the rice huskers used in the prefecture.To investigate the possibility of cross-contamination, we conducted a factual investigation by testing rice processed by rice huskers that were used in Fukushima Prefecture until the nuclear disaster. We measured the total radioactive cesium concentration (¹³⁴Cs + ¹³⁷Cs) in rice samples after processing by the rice huskers. We found the brown rice processed in earlier tests contained higher concentrations of radioactive cesium than the control brown rice which was grown in the same paddy as the samples processed by clean rice husker, and the concentration in the samples gradually decreased as the rice husking tests progressed. After the tests were completed, we disassembled the rice huskers and cleaned each part. While cleaning, we collected residues in order to measure the total radioactive cesium concentration inside the huskers. We found the residues had cesium concentrations much higher than those of the brown rice in our test samples. Moreover, we found that the radioactive cesium concentration of the rice samples was proportional to the contamination ratio of the residue in the rice samples. Our results revealed the risk of cross-contamination of brown rice when radioactive cesium residues are not cleaned from the inside of rice huskers. In order to effectively avoid radioactive cross-contamination, residues should be cleaned from rice huskers before use.

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Because of the escalating price of fossil fuels, heat-pump systems for greenhouse heating have become widespread. Such systems are reported to be capable of decreasing energy costs, which have led to their widespread installation. However, a comparison of the heating load of a heat-pump system with that of a fossil-fuel-fired heater has not been reported so far.In general, the hot air blower in a heat-pump system for greenhouse heating differs from that in a fossil-fuel-fired heater. Therefore, in this study, the heating load and heat loss on the soil surface of a heat-pump system, which releases hot air directly, was compared with that of a fossil-fuel-fired heater, which releases hot air using air ducts. The results can be summarized as follows: 1)The heating load of the heat-pump system (Q_grn) was approximately 80 % that of the fossil-fuel-fired heater (Q_oil ). 2)The observed heat loss on the soil surface of the greenhouse equipped with a heat-pump system (H_{grn -1}) was less than that of the greenhouse equipped with a fossil-fuel-fired heater with ducts (H_{oil -1}). 3)Differences between Q_grn and Q_oil increased with an increase differences between H_{grn -1} and H_{oil -1}.

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