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Use of recycled organic wastes as nutrient sources to aid the growth of energy crops on brownfield sites

Page, Katherine Esther 2014. Use of recycled organic wastes as nutrient sources to aid the growth of energy crops on brownfield sites. PhD Thesis, Cardiff University.
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This thesis presents the results of research into the use of Recycled Organic Wastes (ROWs) as soil amendments to aid the growth of energy crops on brownfield sites in the UK. In order to divert biodegradable waste from landfills, food waste is source segregated by households or is mechanically separated from mixed Municipal Solid Waste (MSW) before being biologically decomposed to form stable ROWs. The source of waste stream influences the future market and use of ROWs. Three different ROWs were characterised to assess the effect of the initial waste stream and the influence of aerobic or anaerobic biodegradation processes on the final organic products. Growth trials were conducted to assess the use of ROWs as nutrient sources for three fast growing tree species, S.viminalis, E. nitens and P. tomentosa. Preliminary growth trials found that high total dissolved solids were associated with some ROWs were detrimental to plant health and survival rates. Further growth trials identified the optimum total nitrogen application rate of ROWs when mixed with Kettering Loam, a clay loam. Analysis of leachate collected from the pot trials identified changes in quantities of heavy metal and nitrogen leaching during the growth trials and allowed comparison to water quality limits for aquatic life to assess the risk to the wider environment. Column growth trials assessed the effect of saturated and unsaturated conditions on a specific ROW known as Compost- Like Output derived from MSW, the impact on plant growth and the effect on leachate composition. Saturated conditions were detrimental to E. nitens, whereas S. viminalis adapted to saturated conditions with greater biomass production compared to the unsaturated columns. A reducing environment resulted in differences in heavy metal leaching and nitrogen forms compared to the unsaturated columns. The use of ROWs on brownfield sites can improve the overall soil quality while providing sufficient nutrients to improve biomass yields of energy crops. However the source of ROWs and biological treatment methods can influence the characteristics and future use of the ROWs. CLO derived from MSW had significantly higher heavy metal concentrations than source segregated material. Higher concentrations of heavy metal, particularly of copper, zinc and lead were identified within the fines (< 1 mm) of MSW derived CLO. Leachate analysis from the optimum and column growth trials identified changes within the pore water chemistry, which also influenced the mobility of heavy metals. The application of ROWs to brownfield sites has the potential to release soluble nitrogen forms and heavy metals into the wider environment; however application to contained sites or lower applications will reduce the risk.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Engineering
Subjects: T Technology > TP Chemical technology
Uncontrolled Keywords: Recycled organic waste; Compost; Heavy Metals; Willow (Salix Viminalis); Euczlyptus nitens; Nitrogen.
Date of First Compliant Deposit: 30 March 2016
Last Modified: 19 Mar 2016 23:46

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