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Title: Quality enhancement of compost using vermicomposting and air separation
Author: Ali, Muhammad
ISNI:       0000 0004 2750 6204
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2007
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European and National legislations in the UK have created a tremendous pressure on the waste management industry for a major expansion of the composting industry over recent years. Also, with the greater awareness of the health and environmental safety within the community, compost producers are forced to provide an authenticated form of quality compost to the consumers. The work presented in this thesis focuses on quality enhancement of mature green-waste derived compost using vermicomposting and air separation techniques. A vermicomposting trial was conducted for a period of 18 weeks by utilising re-hydrated mature green-waste compost produced at Carmarthenshire Environmental Resource Trust (CERT) composting facility as a feedstock. It was found that a minimum average compost mass reduction of 16% was observed by using an average mass throughput of 32.6 kg m 2 week"1. The greatest reduction in volatile solids was observed only during the initial stages of the trial. However, no significant reduction was noted towards the end of the vermicomposting process, when worm mass had reduced to approximately 1.3 kg/m . Replicated growth trials on coriander and tomato were conducted using two commercially available multipurpose composts and five waste-derived composts. It was found that commercial composts showed better plant growth when compared to waste-derived composts. This was followed by another set of growth trials undertaken with lettuce, using pure worm casts (VC), green waste compost (FS) and mixtures of the two Le. 50/50 and 20/80 (VC:FS, v/v) mix. Results showed that plant biomass production was optimal with 20/80 (v/v) mix, whilst VC and FS yielded poor plant growth. In general, the vermicomposting process did not result in an increased availability of nutrients or potentially toxic elements, the only exception being Zn. Characterisation studies were also conducted on unscreened mature compost samples to identify the physical contaminants followed by laboratory and commercial scale air separation trials. Of the coarser fraction from Bryn Pica compost, 1% of plastic film was found. The laboratory air separation trial showed that at the minimum average air velocity of 4.24 m/s, 100% plastic film was removed along with 73% of <10 mm CERT compost During the commercial scale trial, it was found that following screening, the <25 mm fraction would meet the physical contaminant limits of the BSI PAS-100:2005 standard. The 'Komptech Hurrikan' removed 91% of the light materials from the compost oversize (>25 mm). The air jig trial showed promising results and that, in less than 2 minutes, various sizes of stones were separated from the compost stone mix sample.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available