Nitrous oxide emissions from aerated composting of organic waste.

The composting of high organic content wastes has been shown to produce nitrous oxide (N2O). This study was initiated to investigate the mechanisms of N2O emissions from aerated composting and to determine the optimal operational conditions that minimize N2O emissions. The results of our experiment in laboratory-scale composters showed that more than 95% of N2O was produced during the later period of composting when readily available carbon sources had been depleted. Significant increases in N2O emission after nitrite (NO2-) addition, and good NO(2-)-N2O correlation, indicates that N2O was transformed from NO2-. Extremely high N2O generation was observed after NO2- addition in the presence and absence of composted cattle manure. This suggests an identical mechanism for N2O production in both treatments. However, the addition of composted cattle manure resulted in an earlier initiation of the main N2O generation period. Intermittent feeding of fresh food waste postponed the main N2O generation period, and reduced the mass-based N2O emissions by 20%.

Measurements of N2O and CH4 from the aerated composting of food waste.

Emissions of N2O and CH4 from an aerated composting system were investigated using small-scale simulated reactors. The results show relatively high emissions of N2O at the beginning of composting, in proportion to the application amount of food waste. After 2 days, the N2O emission decreased to 0.53 ppmv on average, near to the background level in the atmosphere (0.45 ppmv). The addition of composted cattle manure increased N2O emissions not only at the beginning of composting, but also during the later period and resulted in two peak emission curves. Good correlation was observed between the N2O concentration at the air outlet and NO2- concentration in waste, suggesting a generation pathway for N2O from NO2- to N2O. Methane was only detected in treatments containing composted cattle manure. The high emission of methane illustrates the involvement of anoxic/anaerobic microorganisms with the addition of composted manure. The result suggests the existence of anoxic or anaerobic microsite inside the waste particles even though ventilation was employed during the composting process.

[Evaluation of subrenal capsule assay (SRC) for clinical cancers].

For clinical cancers of esophagus (10 cases), stomach (7), colon and rectum (11) and breast (5), subrenal capsule assays (SRC) were performed using normal or AF nude mice. The sensitivity of anticancer drugs (UFT, CDDP) was evaluated by both the change in graft size under the renal capsule and the histological findings of these grafts. SRC was found to be a very reliable testing method for cancer of esophagus, colon and rectum because these grafts possessed remarkable viability. Evaluability of these two cancers was very high (approximately 80%). Sensitivity of UFT was 29% (2/7) for esophageal cancer, 50% (5/10) against colon and rectal cancer, and that of CDDP was 40% (2/5) and 17% (1/6), respectively. Evaluability of gastric and breast cancers was very low because of the poor growth of the grafts irrespective of the immunity of host animals. It was discussed why the evaluation rate depended on the type of cancer. These results suggest that indications for SRC are restricted, but that for colon and rectal or esophageal cancer SRC is a reliable testing method for anticancer drugs in clinical use.

[Electron microscopic study on the method of evaluation of SRC assay].

The subrenal capsule assay (SRC) is a rapid and precise method for evaluation of chemotherapeutic agents. However, it seems to present some difficulties with regard to sensitivity, since evaluation is done by measurement of graft size. In this study, SRC was performed on six clinical cases of colorectal cancer using nude mice, which were given UFT 15 or 20 mg/kg orally or 2.5 mg/kg CDDP subcutaneously for 2-6 days. Histological changes in the grafted tumors were then observed by electron microscopy. Mucous granules and other features were assessed for evaluation of assay sensitivity. The number of mucous granules seemed to be the most reliable parameter that paralleled the sensitivity evaluated by tumor diameter. Other features such as nuclear mitosis, lysosomal increment and abnormal accumulation of ribosomes, had little correlation with sensitivity. However, further exploration is warranted with regard to local defects of the cytoplasm. This ultrastructural examination suggested that grafted tumor cells were damaged slightly by implantation under the renal capsule, and that the SRC using tumor size as a parameter is clinically useful under conditions where the tumor xenografts show good viability and proliferation in the control group.