Thermal desorption techniques for the analysis of trace level VOC's in landfill gas.

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Allen, M.R., 1998. Thermal desorption techniques for the analysis of trace level VOC's in landfill gas. PhD, Nottingham Trent University.

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Abstract

Landfill gas is a product of the natural biological decomposition of organic material contained in waste deposited in landfills. The predominant gases released during the decomposition processes are carbon dioxide (30-35%) and methane (60-65%) together with a large number of trace volatile organic compounds. The resulting mixture is assigned the generic description of "Landfill Gas". The aim of the work described in this thesis was to develop a method for the analysis of all of the VOC's present in landfill gas, then briefly assess the environmental implications of their release into the atmosphere.

The method developed utilised automated thermal desorption - gas chromatography - mass spectrometry. Preconcentration of the trace VOC's was achieved by using a sandwich of three adsorbents, Tenax TA, Chromosorb 102 and Carbosieve SIII. The latter adsorbents were selected on the basis of breakthrough volume measurements conducted for twelve compounds representative of the trace VOC's identified in landfill gas. Field trials of the developed method were conducted at seven UK landfill sites. Over 140 compounds were detected, of which more than 90 were common to all seven sites. The groups of compounds and concentrations observed were alkanes (302-1543mgm-3), aromatic compounds (94-1906mgm-3), cycloalkanes (80- 487mgm-3), terpenes (35-652mgm-3), alcohols and ketones (2-2096mgm-3) and halogenated compounds (327-1239mgm-3). The observed variations in landfill gas composition were largely attributed to differences in the waste composition and the stage reached in the decomposition processes at each of the sites. Three sites were found to have total chlorine concentrations, derived from the organochlorine compounds in the gas, of above 250mgm-3. Chlorine contents of this level were considered to be potentially damaging to gas fuelled engines used for electricity generation. Chloroethene (<0.1-87mgm-3) was identified as being the most abundant toxic component. Chloroethene levels in the landfill gases sampled from two of the sites studied were found to be in excess of the UK maximum exposure limit by a factor of five and three. Total VOC's emissions from four of the seven sites was estimated to be of the order 104 kg/year. An analytical system for remote monitoring of the VOC's utilising thermal desorption - FTPAS is proposed and the relative advantages and disadvantages discussed.
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Item Type:

Thesis

Creators:

Allen, M.R.

Date:

1998

ISBN:

9781369314199

Identifiers: