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Title: The aerobic treatment of organic wastes and their use in industry
Author: Farrell, Mark
ISNI:       0000 0004 2691 1582
Awarding Body: Bangor University
Current Institution: Bangor University
Date of Award: 2009
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The production of large amounts of Municipal Solid Waste (MSW) is an inevitable consequence of today's consumer society. Finding safe, sustainable, socially acceptable and cost effective alternatives to the disposal of MSW in landfills represents a major challenge to the waste management industry, and one that was set out in law under the European Landfill Directive in 1999. Composting is seen as an attractive waste management option, providing that there are few negative effects on the environment after undertaking a life cycle assessment. The focus of the research presented in this thesis is on the composting of MSW, both mixed and source-segregated, and the subsequent use of these composts in the remediation, land reclamation and horticultural industries. Composts were produced in two runs on an industrial scale using the EcoPOD® in-vessel composting system, and changes in key compost quality indicators (e.g. C:N ratio, nutrient and heavy metal availability) were quantified during the composting process (Chapters 3 & 6). Due to UK regulations on wastes containing animal by-products, no field trials were possible using the composts produced in the studies presented in this thesis. Instead, a series of pot trials were carried out over Chapters 3-6, with a mesocosm-scale trial used in Chapters 7 & 8. Of these trials, Chapter 3 investigated potential uses for mixed-waste compost produced using the EcoPOD® system, and found it to be particularly suited to remediation of acidic, heavy metal contaminated soils. This theme of remediation was carried on through Chapter 4 on the pot scale, and Chapters 6 & 7 on a mesocosm scale studying migration of heavy metals down the soil profile over time. Work in Chapter 5 focussed on the difficult subject of ecologically sensitive revegetation of blocky slate waste using composts amended with sulphur and iron hydroxide to make them more suitable for upland restoration purposes. Analysis of soil solution pH and P concentration proved promising with pH being decreased by s0, and P being reduced by Fe(OHh, however the amendments failed to influence above-ground plant diversity trajectories. Finally, nutrient rich composts produced in Chapter 6 was assessed for their potential as a replacement for peat in horticulture, and demonstrated that a 75 % substitution for peat based growing media is possible without affecting plant growth and yield. In summary, this work has demonstrated that highly contrasting organic wastes can be successfully composted, and has found that even low-quality mixed waste composts may be successfully used in the biostabilisation of acidic, heavy metal contaminated soils. In fact, the high buffering capacity of the MSW compost produced in this study (Appendix 1) lends itself to this role, providing a strong ability to resist pH change from the pyritic nature of the soil used throughout these studies (Chapters 3, 4, 6 & 7) . In order to assess the contribution of compost-borne heavy metals to the overall burden, further work using isotopic analysis could be utilised to pinpoint contaminant sources (Appendix 2). The use of chemical amendments to reduce compost pH and P availability showed promise, but further work is required in this area to optimise the amendments. Finally, composts derived from catering wastes w ere found to provide a real alternative to peat in horticulture, although such wastes are yet to attain full market acceptance.
Supervisor: Jones, David Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available