Vermicomposting-Enhancing the quality of compost derived from green waste?

摘要

A vermicomposting trial was conducted for 18 weeks using commercially produced green waste-derived compost as the feed material. The aim of the study was to investigate the extent to which a combination of vermicomposting and the traditional windrow composting of green waste may be performed, in order to enhance the value of the final product. Two identical reactor beds (A and B) were constructed and fed with mature screened compost (< 10 mm) that was re-hydrated to a moisture content of 60 ± 2 % before vermicomposting using Denbrobeana veneta. The objective was to enhance the product quality at maximum throughput and waste processing capacity, therefore, a high stock density 7 kg/m~2 of earthworms was used. The reduction in earthworm biomass obtained is reported at various stages during the trial. An average mass throughput of 32.6 kg/m~2/week was achieved and overall mass reductions of 24 % and 20 % were observed for reactor A and B respectively at the end of trial. The rate of organic matter decomposition was also determined by measuring volatile organic matter of feedstock and casts material. The greatest reduction (35%, m/m) was observed during the initial stages of trial. However, no significant reduction was noted towards the end of vermicomposting process, when worm mass had reduced to approximately 1.2 kg/m~2. Minor changes were observed for pH, electrical conductivity and redox potential. The temperature within the reactor bed remained within optimum range i.e. 15 to 23 °C. Chemical analysis of the total and bio-available nutrients and heavy metals concentrations of the substrate and casts materials before and after the treatment are also reported.