An analysis of the factors affecting landfill gas composition and production and leachate characteristics at the Vancouver Landfill Site at Burns Bog
Creators: name: Wreford, Katherine
Publisher: name: University of British Columbia
Year: 2009

description: Landfill gas represents either a significant contributor to the build-up of greenhouse gases in the troposphere when released, or a potential energy source when recovered. An analysis of variation in landfill gas production and composition (%CH₄, %C0₂) in response to variations in ambient temperature, precipitation, barometric pressure and refuse age was carried out at the Vancouver Landfill Site at Burns Bog, located in Delta, B.C.. Results indicate that precipitation is a predominant factor, as illustrated in the relationship between cumulative precipitation 14 days prior to sampling and CH₄ generation (mean r2=0.88). This finding suggests that a time lag is in effect wherein the moisture acts to enhance the anaerobic nature of the niche, increase the mixing and availability of carbon rich organic matter and nutrients, directly stimulate bacterial growth and dilute metabolic inhibitors, leading to increased CH₄ production. Ambient temperature displayed only a moderate correlation with CH₄ production (mean r2=0.41), likely due to the establishment of a relatively consistent microclimate within the waste matrix. High gas temperatures were observed to correspond with periods of peak CH₄ production. Fluctuations in barometric pressure were not seen to have an effect on landfill gas production at the p=0.05 level of significance. Refuse age showed some relationship to CH₄ production, but results of this were inconclusive. Regression equations were calculated to predict CH₄ production from the sample gas ports and gas collection lines. Total annual CH₄ production from this site was calculated to be 44.76 kT, which equates to approximately 3% of the total CH₄ produced by landfills in Canada. Results suggest that the potential does exist for the optimization of waste degradation within the matrix. The production ratio of CH₄:C0₂ showed a strong relationship to cumulative precipitation 7-days prior to sampling (r2=0.85), with the relatively high ratio following periods of heavy rainfall. It is likely that conditions of low hydraulic retention time cause the CO₂ to be dissolved from the matrix and flushed downward with the movement of the leachate. It is also possible that the CO₂ acts as an end-product inhibitor during acetate and propionate degradation; its decreased partial pressures after periods of heavy rainfall would thus favour enhanced CH₄ production. Leachate parameters displayed high variability. COD concentrations were observed to decrease following heavy rainfall. Loadings of both NH4 + -N and acetic acid were observed to increase with higher precipitation inputs, most likely due to the increased mobilization of the substances. Both NH4 + -N and acetic acid loadings were found to increase significantly with increasing CH₄ production. Once again, it is likely that the "washing" of the matrix following periods of heavy rainfall (and increased CH₄ production) is responsible for this observation.