Abstract:

In order to investigate the effects of turning frequency on composting process and chemical and physical properties of spent Chinese herbal medicine, a pilot scale windrow trial was run for 80 days to test the variations of temperature, total contents of carbon, nitrogen, phosphorus, potassium, C/N ratio, pH, GI and apparent properties and compost quality during composting process of spent Chinese herbal medicine at different turning frequencies. There were six treatments: no turning (A1), once per five days (A2), once per ten days (A3), once per fifteen days (A4), once per twenty days (A5) and once per twenty-five days (A6). The results were obtained as following: the longest duration of high temperature (≥50℃) was found in A3, up to 44 days. Compared to A1, carbon contents of A4, A5, and A6 were reduced by 0.35%, 1.73% and 1.61%, respectively. Total nitrogen contents of A2, A3, A4 and A6 reduced by 5.32%, 8.40%, 5.25% and 1.44%, respectively; while total phosphorus contents of A2, A3, A4, A5, and A6 increased by 4.82%, 9.64%, 6.83%, 8.03% and 2.01%, respectively, and total potassium content of A2, A3, A4, A5 and A6 increased by 6.18%, 5.38%, 2.96%, 8.33% and 8.03%, respectively. GI increased by 35.15%, 33.23%, 31.3%, 28.89% and 17.01%, respectively, but variations of C/N and pH in six treatments had small differences. Carbon content of matured compost of spent Chinese herbal medicine was 36.0%, and nitrogen content was 25.97%, 17.12%, 28.81%, 41.20% and 41.91% higher than swine manure, chicken manure, sheep manure, duck and goose excrement, respectively. In comprehensive analysis of the factors evaluated, our research concluded that the turning frequency of once per ten days should be recommended for a pilot scale of windrow composting of Chinese herbal medicine.