Using natural clinoptilolite zeolite as an amendment in vermicomposting of food waste

Abstract

The effect of adding different proportions of natural clinoptilolite zeolite (5 and 10%) to food waste vermicomposting was investigated by assessing the physicochemical characteristics, worms' growth, and maturation time of finished vermicompost in comparison with the vermicompost prepared with no amendment (control). Vermicomposting was performed in 18 plastic containers for 70 days. The experimental results showed that the carbon-to-nitrogen (C/N) ratios were 15.85, 10.75, and 8.94 for 5 and 10% zeolite concentration and control after 70 days, respectively. The addition of zeolite could facilitate organic matter degradation and increase the total nitrogen content by adsorption of ammonium ions. Increasing the proportion of zeolite from 0% (control) to 10% decreased the ammonia escape by 25% in the final vermicompost. The natural zeolite significantly reduced the electrical conductivity (EC). At the end of the process, salinity uptake efficiency was 39.23% for 5% zeolite treatment and 45.23% for 10% zeolite treatment. The pH values at 5 and 10% zeolite-amended treatments were 7.31 and 7.57, respectively, in comparison to 7.10 in the control. The maturation time at the end of vermicomposting decreased with increasing zeolite concentration. The vermicompost containing 5 and 10% zeolite matured in 49 and 42 days, respectively, in comparison to 56 days for the control. With the use of an initial ten immature Eisenia fetida worms, the number of mature worms in the 10% zeolite treatment was 26 more than that in the 5% zeolite treatment (21 worms) and 9 more than that in the control treatment (17 worms). Significantly, natural zeolite showed a beneficial effect on the characteristics of the end-product when used in the vermicomposting of food waste.