skip to main content

Title: CO2 Sequestration using BOF slag: Application in landfill cover
Fugitive methane (CH4) and carbon dioxide (CO2) emissions at municipal solid waste (MSW) landfills constitute one of the major anthropogenic sources of greenhouse gas (GHG) emissions to the atmosphere. In recent years, biocovers involving the addition of organic-rich amendments to landfill cover soils is proposed to promote microbial oxidation of CH4 to CO2. However, most of the organic amendments used have limitations. Biochar, a solid byproduct obtained from gasification of biomass under anoxic or low oxygen conditions, has characteristics that are favorable for enhanced microbial oxidation in landfill covers. Recent investigations have shown the significant potential of biochar-amended cover soils in mitigating the CH4 emissions from MSW landfills. Although the CH4 emissions are mitigated, there is still considerable amount of CO2 that is emitted to the atmosphere as a result of microbial oxidation of CH4 in landfill covers as well as the CO2 derived from MSW decomposition. Basic oxygen furnace (BOF) slag is a product of steel making has great potential for CO2 sequestration due to its strong alkaline buffering and high carbonation capacity. In an ongoing project, funded by the U.S. National Science Foundation, the potential use of BOF slag in landfill covers along with biochar-amended soils to mitigate more » both CH4 and CO2 emissions is being investigated. This paper presents the initial results from this study and it includes detailed physical and chemical and leachability characteristics of BOF slag, and a series of batch tests conducted on BOF slag to determine its CH4 and CO2 uptake capacity. The effect of moisture content on the carbonation capacity of BOF slag was also evaluated by conducting batch tests at different moisture contents. In addition, small column experiments were conducted to evaluate the gas migration, transport parameters and the CO2 sequestration potential of BOF slag under simulated landfill gas conditions. The result from the batch and column tests show a significant uptake of CO2 by BOF slag for the tested conditions and demonstrates excellent potential for its use in a landfill cover system. « less
; ; ; ;
Award ID(s):
Publication Date:
Journal Name:
International Conference on Protection and Restoration of the Environment XIV
Sponsoring Org:
National Science Foundation
More Like this
  1. The municipal solid waste (MSW) in landfills undergoes anaerobic decomposition to produce landfill gas (LFG), which predominantly consists of methane (CH4) and carbon dioxide (CO2). Fugitive LFG emissions which are otherwise not targeted by gas collection system escape into the atmosphere, forming one of the largest anthropogenic sources of CH4 and CO2 emissions in the United States. The landfill cover soil plays an important role in mitigating the LFG emissions by microbial oxidation of CH4 to CO2 thereby reducing the CH4 emissions to atmosphere. Several researchers have investigated the addition of organic amendments to the cover soils in order tomore »enhance microbial oxidation of CH4 in landfill covers. In recent years, biochar as an organic amendment has shown promise in enhanced microbial oxidation due to its inert/stable chemical nature to degradation, high surface area, high internal porosity, and high moisture holding capacity. However, in all these efforts there is no regard given to the CO2 that still escapes into the atmosphere in undesirable amounts. Steel slag, a product from steel making industry, due to its high alkaline buffering capacity, high carbonation potential, and its unique cementitious properties has found numerous applications in civil and environmental engineering. But, until now there has been no study on the potential use of steel slag in landfill covers to sequester the CO2 emissions. Ongoing research study, funded by the U.S. National Science Foundation, explores the use of BOF steel slag in conjunction with biochar amended cover soil so as to first convert CH4 to CO2 by microbial oxidation and thereafter sequester the resulting CO2 from CH4 oxidation and the prevailing CO2 from anaerobic decomposition together by steel slag, thereby significantly mitigating the LFG emissions from landfills. In this paper, a review on the current applications and carbon sequestration mechanisms of BOF steel slag is presented. Finally, the proposed concept of the biogeochemical soil cover for mitigation of LFG emissions and some of the results from a preliminary investigation indicating the CO2 sequestration potential by steel slag are discussed.« less
  2. Among many anthropogenic sources of greenhouse gases (GHG), landfill emissions, consisting of methane (CH4) and carbon dioxide (CO2), are one of the major contributors of anthropogenic GHG. In recent years, various innovative landfill biocovers have been investigated and developed to mitigate the emissions of methane (CH4) from municipal solid waste (MSW) landfills. However, the problem of CO2 emissions [which constitute about 40% of landfill gas (LFG)] from MSW landfills still remains unresolved. An innovative cover system which consists of basic oxygen furnace (BOF) slag with biochar amended soil is being developed to mitigate CH4 and CO2 emissions from landfills. Themore »biochar amended soil is effective in mitigating CH4 emissions by microbial methane oxidation, while BOF slag could be effective in sequestering CO2 emissions by carbonation mechanisms. However, the properties of BOF slag vary based on several factors such as mineralogical composition of slag, particle size, moisture content, and temperature. In this study, CO2 sequestration potential of BOF slag was evaluated under synthetic LFG condition. The performance of the BOF slag in sequestering CO2 under different moisture condition was also examined. The results showed that BOF slag can sequester substantial amount of CO2 under LFG condition. The study also enlightened the importance of moisture for initiating carbonation reaction; however, the moisture alone was not the controlling parameter for CO2 sequestration. The mineralogy of the BOF slag plays an important role in determining CO2 sequestration capacity of the slag.« less
  3. Municipal solid waste (MSW) landfills are regarded as one of the major sources of greenhouse gas (GHG) emissions across the world. In order to control these emissions, an innovative and sustainable biogeochemical cover system that consists of soil, biochar and basic oxygen furnace (BOF) slag is being developed to completely eliminate fugitive methane (CH4) and carbon dioxide (CO2) emissions from the landfills. The effectiveness of such cover systems is highly dependent on the survival and activity of methanotrophs under highly alkaline conditions induced by the presence of slag. In this study, a series of microcosm batch tests on landfill covermore »materials in different proportions were investigated to study the effect of cover materials on microbial CH4 oxidation in the mixed as well isolated systems. Results demonstrated negligible CH4 oxidation and substantial CO2 sequestration when the BOF slag was integrated/mixed with soil (pH~7) and biochar-amended soil (pH~11). However, layered or separated cover material conditions (biochar-amended soil overlain by slag and soil overlain by slag) demonstrated promising CH4 oxidation potential, thus concluding that extreme alkaline conditions inhibit the CH4 oxidation. Overall, this study showed that a layered system consisting of the soil or biochar-amended soil layer overlain by BOF slag layer is optimal for CH4 oxidation and subsequent CO2 sequestration. Large column experiments and field test plots are being performed to evaluate the long-term performance of the proposed geochemical cover system under dynamic environmental (moisture and temperature) conditions.« less
  4. Municipal solid waste (MSW) landfills are known to be one of the major sources of greenhouse gas (GHG) emissions into the atmosphere. In order to alleviate these emissions, an innovative biogeochemical cover system is proposed to mitigate both methane (CH4) and carbon dioxide (CO2) emissions, which are the predominant gases in landfill gas (LFG) emissions. This paper investigates four materials: soil, non-activated biochar, methanotrophic activated biochar, and basic oxygen furnace (BOF) slag for their CH4 and CO2 uptake capacity. First, the physical and chemical properties of the four materials were tested. Thereafter, several series of batch tests were conducted tomore »determine CH4 and CO2 uptake by each material. The results demonstrate that the soil has the potential to oxidize CH4 into CO2 due to presence of CH4 oxidizing (methanotrophic) bacteria, while the BOF steel slag has potential to sequester CO2. The methanotrophic activated biochar showed enhanced biological activity due to high methanotrophic population, mitigating CH4 efficiently. However, the non-activated biochar had little to no effect on the uptake of either CH4 or CO2. Finally, the combination of these cover materials at different proportions in different configurations is being investigated to optimize the biogeochemical cover system to mitigate both CH4 and CO2 emissions.« less
  5. In the USA, municipal solid waste (MSW) landfills constitute one of the major anthropogenic sources of methane emissions. In the landfill cover soils employed at MSW landfills, aerobic methane-oxidizing bacteria (MOB) convert CH4 to CO2, thereby partially mitigating the CH4 emissions to the atmosphere. In this study, culture-dependent and culture-independent techniques were employed to evaluate methane oxidation capacity and to characterize the microbial community in landfill cover soil. Microcosms with synthetic landfill gas headspace were used to measure potential methane oxidation rates in landfill cover soil and in methanotrophs-enriched microbial consortia. The results demonstrate that the enriched landfill cover soilmore »supported the growth of a diverse group of methanotrophic and methylotrophic microorganisms, and were dominated by Type I methanotrophs showing positive correlation with CH4 oxidation rates.« less