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Calcite precipitation in landfills: An essential product of waste stabilization

Lookup NU author(s): Professor David Manning

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Abstract

Routine monitoring of landfill leachates has been extended to include characterization of suspended solids recovered by filtration. Calcite is consistently identified as a suspended solid, with less frequent reports of quartz and clays (kaolinite, illite, chlorite). Morphologically, calcite occurs as discrete grains, coatings on quartz sand and as microconcretions. Preliminary stable isotope data for seven samples generally show positive δ 13C values (relative to PDB) up to +3.5‰ and δ18O values between -5 and -8‰, consistent with an origin through precipitation from leachate. Geochemical modelling of leachate compositions for the same samples indicates that the leachates are saturated with respect to calcite, and that the degree of supersaturation decreases for older samples. Mass balance considerations show that the proportions of methane and carbon dioxide observed for landfill gas do not reflect the amount of bicarbonate that is potentially available from the anaerobic of decomposition of putrescible waste. Overall, putrescible waste has the potential to form a maximum of 1.9 g of calcite for every gram of waste, although values less than this are likely to be achieved in practice. From these differing lines of evidence, there can be no doubt that calcite precipitation should be expected to take place within landfill systems as an essential part of the waste degradation and stabilization process, and should be considered in modelling both gas evolution and carbon emissions.


Publication metadata

Author(s): Manning DAC

Publication type: Article

Publication status: Published

Journal: Mineralogical Magazine

Year: 2001

Volume: 65

Issue: 5

Pages: 603-610

Print publication date: 01/10/2001

ISSN (print): 0026-461X

ISSN (electronic): 1471-8022

Publisher: Mineralogical Society

URL: http://dx.doi.org/10.1180/002646101317018424

DOI: 10.1180/002646101317018424


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