Steven John Warwick

Research

Research interests

My research interests include methods for the identification of resources within landfills, routes to compute their potential value and how these can be exploited. This also forms part of my PhD research. I am also interested in the general concept of urban mining particularly at the molecular level.

Thesis

A Study of Landfill Content and its Chemical Evolution Using Historical, Geographic and Site Monitoring Data

Historical landfills present a paradoxical position where, on the one hand, their impact on the environment is overtly negative and, on the other are seen as potential stores of value. Intrusive investigation to identify a landfill’s resource potential is expensive and, due to the heterogeneity of content, has significant uncertainty. This thesis proposes a solution using historical data to identify the quantities and types of materials entering landfills. However, it is accepted that recording of waste data was limited and exactly how much or what data exists is typically answered anecdotally. This study considers the problem from a formal research perspective by collecting and reviewing historical waste data. Data collection focussed on 4 areas: i) contemporary landfill emissions monitoring and waste import data, ii) historical data leading to waste generation, iii) historical disposal data and iv) historical municipal waste composition data. In each case, a significant quantity of data was discovered and reviewed.

Initially, using historical data, 4 discrete epochs were identified where contemporary determinants impacted on i) the materials forming waste ii) the quantities of waste generated iii) waste disposal and iv) regulatory controls. For the first two epochs, waste flows into landfills were determined by waste composition. The third epoch witnessed a transition from composition to regulation with regulation becoming the controlling factor in the fourth. Such classification enabled the data for use i) as surrogates for missing data and ii) as inputs to a system dynamics model that estimates weights for generated and landfilled MSW for England (1.051 billion tonnes and 885 million tonnes respectively) and provides quantities of MSW components disposed to landfill.

Contemporary data included leachate monitoring data for 2 landfills operational since 2005 and 2007 and regulated by the 1999 Landfill Directive whereby the European Union proposed diversion of putrescible waste away from landfill. When decomposing, putrescible MSW reduces the pH of a landfill’s environment. Landfill decomposition progresses through a series of phases where this low pH phase or acetogenesis has been shown to inhibit the development of methanogenic bacteria. Analysis of the data identified this low pH phase did not occur at these landfills whereby they provided a possibly singular opportunity to report this anticipated phenomenon to the research community.

The scale of the problem should not be underestimated. The Environment Agency lists some 22,000 historic landfill sites for England. If we include Europe, this extends to some 500,000 sites with a waste volume lying between 50 - 80 billion m3. The contents of these sites range from inert materials to municipal solid waste (MSW) and many include an array of hazardous substances. Many were completed long before records were kept.

Supervisors

Publications

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