Department of Civil, Materials, and Environmental Engineering, University of Illinois Chicago, 842 West Taylor Street, Chicago, IL, 60607, USA.
Environ Sci Pollut Res Int. 2024 Aug;31(38):50782-50803. doi: 10.1007/s11356-024-34558-2. Epub 2024 Aug 5.
Municipal solid waste (MSW) landfills are a significant source of methane (CH) emissions in the United States, contributing to global warming. Current landfill gas (LFG) management methods, like the landfill cover system and LFG collection system, do not entirely prevent LFG release. Biocovers have the potential to reduce CH emissions through microbial oxidation. However, LFG also contains carbon dioxide (CO) and trace hydrogen sulfide (HS) depending on waste composition, temperature, moisture content, and age of waste. An innovative biogeochemical cover (BGCC) was developed to tackle these concerns. This cover comprises a biochar-based biocover layer overlaid with a basic oxygen furnace (BOF) steel slag layer. The biochar-based biocover layer oxidizes CH emissions, while the BOF slag layer reduces CO and HS through carbonation and sulfidation reaction mechanisms. The BGCC system's field performance remains unexamined. Therefore, a large-scale tank setup simulating near-field conditions was developed to evaluate the BGCC system's ability to mitigate CH, CO, and HS from LFG simultaneously. Synthetic LFG was passed through the BGCC in five distinct phases, each designed to simulate the varying gas compositions and flux rates typical of MSW landfill. Gas profiles along the depth were monitored during each phase, and gas removal efficiency was measured. After testing, biocover and BOF slag samples were extracted to analyze physico-chemical properties. Batch tests were also conducted on samples extracted from the biocover and BOF slag layers to determine potential CH oxidation rates and residual CO sequestration capacity. The results showed that the BGCC system's CH removal efficiency decreased with higher CH flux rates, achieving its highest removal (74.7-79.7%) at moderate influx rates (23.9-25.5 g CH/m-day) and reducing to its lowest removal (27.4%) at the highest influx rate (57.5 g CH/m-day). Complete HS removal occurred during Phase 3 in the biocover layer of BGCC system. CH oxidation rates were highest near the upper (277.9 µg CH/g-day) and lowest in the deeper region of the biocover layer. In the tank experiment, CO breakthrough occurred after 156 days due to drying of the BOF slag layer, with an average residual carbonation capacity of 46 gCO/kg slag after moisture adjustment. Overall, the BGCC system effectively mitigated LFG emissions, including CH, CO, and HS, at moderate flux rates, showing promise as a comprehensive solution for LFG management.
城市固体废物（MSW）垃圾填埋场是美国甲烷（CH）排放的重要来源，对全球变暖有贡献。目前的垃圾填埋气（LFG）管理方法，如填埋覆盖系统和 LFG 收集系统，并不能完全防止 LFG 的释放。生物覆盖层有通过微生物氧化减少 CH 排放的潜力。然而，LFG 还含有二氧化碳（CO）和痕量的硫化氢（HS），具体取决于废物成分、温度、含水量和废物的年龄。一种创新的生物地球化学覆盖层（BGCC）已被开发出来以解决这些问题。该覆盖层由生物炭基生物覆盖层和碱性氧气炉（BOF）钢渣层组成。生物炭基生物覆盖层氧化 CH 排放物，而 BOF 渣层通过碳酸化和硫化反应机制减少 CO 和 HS。BGCC 系统的现场性能尚未经过检验。因此，开发了一个大型罐式装置来模拟近场条件，以评估 BGCC 系统同时减轻 LFG 中 CH、CO 和 HS 的能力。合成 LFG 通过 BGCC 分五个不同阶段进行传递，每个阶段的设计都旨在模拟 MSW 垃圾填埋场中典型的变化的气体组成和通量率。在每个阶段，沿深度监测气体分布，并测量气体去除效率。测试后，提取生物覆盖层和 BOF 渣样品进行分析物理化学性质。还对从生物覆盖层和 BOF 渣层中提取的样品进行了批量测试，以确定潜在的 CH 氧化速率和残余 CO 封存能力。结果表明，BGCC 系统的 CH 去除效率随着 CH 通量率的增加而降低，在适度通量率（23.9-25.5 g CH/m-天）下达到最高去除率（74.7-79.7%），在最高通量率（57.5 g CH/m-天）下降至最低去除率（27.4%）。在 BGCC 系统的生物覆盖层中，HS 在第三阶段完全去除。CH 氧化速率在生物覆盖层的上部最高（277.9 µg CH/g-天），在深部最低。在罐实验中，由于 BOF 渣层干燥，CO 穿透发生在 156 天后，调整水分后，渣层的平均剩余碳酸化能力为 46 gCO/kg 渣。总体而言，BGCC 系统在中等通量率下有效地减轻了 LFG 排放，包括 CH、CO 和 HS，是 LFG 管理的综合解决方案的有希望的选择。
