Coupling between geochemical reactions and multicomponent gas and solute transport in unsaturated media: A reactive transport modeling study

Molins, Sergi; Mayer, K. Ulrich

doi:10.1029/2006wr005206

Cited by 107 publications

(89 citation statements)

References 59 publications

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“…57 can be replaced with the Nernst-Planck equation. Equations 56 and 57 can be expanded to consider transport in phases other that the liquid by adding the corresponding accumulation and transport terms [35,36].…”

Section: Reactive Transport Equationsmentioning

confidence: 99%

Reactive transport codes for subsurface environmental simulation

et al. 2014

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A general description of the mathematical and numerical formulations used in modern numerical reactive transport codes relevant for subsurface environmental simulations is presented. The formulations are followed by short descriptions of commonly used and available subsurface simulators that consider continuum representations of flow, transport, and reactions in porous media. These formulations are applicable to most of the subsurface environmental benchmark problems included in this special issue. The list of codes described briefly here includes PHREEQC, HPx, PHT3D, OpenGeoSys (OGS), HYTEC, ORCHESTRA, TOUGHREACT, eSTOMP, HYDROGEOCHEM, CrunchFlow, MIN3P, and PFLOTRAN. The descriptions include a C. I. Steefel ( ) · B. Arora · S. Molins · N. Spycher

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Section: Reactive Transport Equationsmentioning

confidence: 99%

Reactive transport codes for subsurface environmental simulation

et al. 2014

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“…This requirement is not currently enforced in TMVOC, but was implemented in the code for this work. As noted above, equimolar flux is a reasonable assumption for multicomponent gas transport in high permeability landfill cover soils [Molins and Mayer, 2007b].…”

Section: A) Gas Flow In Landfillsmentioning

confidence: 99%

“…Both models fitted the data well producing nearly identical results, which implied that both Knudsen and nonequimolar diffusion were minor. Simulations using Fick's law in the ADM framework also produced very small errors in this landfill cover soil [Molins and Mayer, 2007b;Molins and Mayer, 2007a].…”

Section: A) Gas Flow In Landfillsmentioning

confidence: 99%

Intelligent Bioreactor Management Information System (IBM-IS) for Mitigation of Greenhouse Gas Emissions

Imhoff¹,

Yazdani²,

Augenstein³

et al. 2010

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Methane is an important contributor to global warming with a total climate forcing estimated to be close to 20% that of carbon dioxide (CO2) over the past two decades. The largest anthropogenic source of methane in the US is "conventional" landfills, which account for over 30% of anthropogenic emissions. While controlling greenhouse gas emissions must necessarily focus on large CO2 sources, attention to reducing CH4 emissions from landfills can result in significant reductions in greenhouse gas emissions at low cost. For example, the use of "controlled" or bioreactor landfilling has been estimated to reduce annual US greenhouse emissions by about 15-30 million tons of CO2 carbon (equivalent) at costs between $3-13/ton carbon. In this project we developed or advanced new management approaches, landfill designs, and landfill operating procedures for bioreactor landfills. These advances are needed to address lingering concerns about bioreactor landfills (e.g., efficient collection of increased CH4 generation) in the waste management industry, concerns that hamper bioreactor implementation and the consequent reductions in CH4 emissions. Collectively, the advances described in this report should result in better control of bioreactor landfills and reductions in CH4 emissions. Several advances are important components of an Intelligent Bioreactor Management Information System (IBM-IS).5 III. Executive SummaryMethane is an important contributor to global warming with a total climate forcing estimated to be close to 20% that of carbon dioxide (CO2) over the past two decades. The largest anthropogenic source of methane in the US is "conventional" landfills, which account for over 30% of anthropogenic emissions. One means of mitigating methane emissions is to operate landfills as "controlled landfills" or "bioreactors." Here, biological conditions in the waste are optimized allowing more rapid and complete waste decomposition. In "anaerobic bioreactors" methane generation is enhanced through liquid addition. High efficiency capture of methane is utilized to maximize fuel energy recovery and minimize fugitive emissions. In "aerobic bioreactors" air and liquid are introduced in the landfill and the combined effects of heat and oxygen inhibit methane formation. Both "controlled" landfill operations hold promise for mitigating fugitive methane emissions from landfills.A recent NETL sponsored economic study of anaerobic controlled landfilling estimated that such landfilling could reduce annual US greenhouse emissions by about 15-30 million tons of CO2 carbon (equivalent) at costs between $3-13/ton carbon. Given the promise of this technology, several bioreactor landfills have been constructed in the United States, although most are fieldscale research landfills. While a few commercial bioreactor landfills have been built, the waste management industry has yet to embrace this technology because of lingering concerns about the capture of fugitive greenhouse gases, how to manage liquid addition to maintain optimal moist...

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“…(2011) Advective fluxes, on the other hand, may be induced by soil-atmosphere barometric pressure gradients causing bulk movement of gasses into or out of soils Poulsen 2003;Massman 2006;Redecker 2015). Pressure gradients may also be induced by reactions; for example the simple stoichiometry of CH 4 oxidation results in a net decrease in pore-gas volume, while the production of CO 2 and CH 4 result in a net increase in pore-gas volume (Molins and Mayer 2007). The direction of flow depends on whether soilatmosphere pressure gradients are positive (atmospheric pressure > pore-gas pressure) or negative (atmospheric pressure < pore-gas pressure) (Elberling et al 1998).…”

Section: Mass Transport Of Pore Gas In Unsaturated Reclamation Cover mentioning

confidence: 99%

Pore-gas dynamics in overburden and reclamation soil covers

ScaleKyle

FlemingIan

2019

Environmental Geotechnics

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Large above-grade overburden landforms comprised of low-grade lean oil sands (LOS) are amassed during the surface mining of oil sands in northern Alberta, Canada. Reclamation soil covers consisting of locally-salvaged soils are subsequently placed above the LOS landforms in single and multi-layered configurations. The soil covers are intended to 1) provide sufficient pore-gas O2 to facilitate the growth of native boreal forest vegetation and to 2) oxidize methane (CH4) produced in the anaerobic zones of the LOS before being exhausted to the atmosphere as a greenhouse gas.Prior to covering the LOS with soil covers, rates of CO2 efflux from the surface of the LOS to the atmosphere ranged from 0.1-7.1 kg/m2/a. Pore-gas concentrations within the uncovered LOS ranged from 0-18% for oxygen (O2), 3-21% for carbon dioxide (CO2), and 0-12% for CH4. Following placement of soil covers, peak rates of CO2 efflux were 2.3 kg/m2/a from the surface of the soil covers to the atmosphere and 1.8 kg/m2/a from the LOS into the soil covers.Peak rates of O2 influx from the atmosphere through the soil covers was 18 kg/m2/a. Poregasses within the overlying soil covers and uppermost LOS were typically below the threshold that poses a risk to the survivability of reclamation vegetation, >10% O2 and <15% CO2. Poregasses deeper than 2 m within the LOS surpassed this threshold with O2 falling to 0% and CO2 rising to >16%.Rates of CH4 oxidation were quantified in batch soil column experiments for the soil cover materials and LOS in single and multi-layered configurations. Oxidation rates were sensitive to variations in temperature, moisture content, and bulk density. The results of the column experiments indicate that CH4 generated deeper than 2 m within the LOS landform will be partially oxidized in both the soil covers and uppermost LOS horizon.Statistical analyses and finite difference numerical modelling were conducted to guide mine operators regarding practical issues involving the construction of LOS landforms, design of soil cover systems, and management of reclamation sites. Based on these exercises, it appears that the characteristics of the LOS landform are more important to pore-gas dynamics than the design of the soil cover systems.iii ACKNOWLEDGEMENTS

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Coupling between geochemical reactions and multicomponent gas and solute transport in unsaturated media: A reactive transport modeling study

Cited by 107 publications

References 59 publications

Reactive transport codes for subsurface environmental simulation

Reactive transport codes for subsurface environmental simulation

Intelligent Bioreactor Management Information System (IBM-IS) for Mitigation of Greenhouse Gas Emissions

Pore-gas dynamics in overburden and reclamation soil covers

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