On some organic constituents of city refuse composts produced in Japan

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Abstract
As part of the research project “Improvement of composting process of municipal refuse and agricultural use of the product,” city refuse composts produced at various cities in Japan were collected and analysed to characterize their organic constituents. Besides these samples, city refuse composts, produced from the same raw materials in the pilot plant, were also analysed to clarify the changes of organic constituents of city refuse during composting process. Compost samples, which have been collected from various cities, included those at different degrees of maturity; their total carbon, carbohydrate contents and carbon-nitrogen ratios showed large variations whereas the total nitrogen contents and the distribution of different forms of nitrogen showed very small variations. Some of these samples showed extremely high carbon-nitrogen ratios and high carbohydrate contents. Furthermore, analytical results on city refuse compost produced from the same raw materials showed that changes of organic constituents of city refuse during composting process were of nearly similar pattern to those of rice straw, however cellulose contents of city refuse composts showed higher values compared with those of rice straw. Composted products, obtained just after the fermentation process, had dreadful reek and were not suitable for handling directly by farmers. Piling the products for two or three months were effective to eliminate this reek and lower the high carbon-nitrogen ratios and the high carbohydrate contents. From the result of this experiment, several problems have been pointed out by the present authors for the improvement of the composting process of city refuse and agricultural use of the products. The points are itemized as follows: (1) Necessity of much longer period of oxidative fermentation process. (2) Necessity of piling the products for two or three months with frequent turnover to keep oxidative conditions. (3) Usefulness of the ratio of carbon in reducing sugars to total carbon, as well as carbon-nitrogen ratio, and content of hot water soluble organic matter to check the degree of maturity of city refuse compost, so far as considerably fresh composts are concerned.