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Development of methods to improve capture of greenhouse gases from bioreactor landfills.

机译：开发了改善从生物反应器垃圾填埋场中捕获温室气体的方法。

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摘要

Landfill methane (CH4) is a potent greenhouse gas contributing to global climate change, and therefore, it should be captured to reduce emissions of greenhouse gases. Collected CH4 can also be used as an alternative energy source. To control landfill gas (LFG) emissions, gas collection systems of various designs have been used. However, the efficiency of LFG recovery systems can be problematic, particularly before installation of final landfill covers. In addition, despite the widespread use of LFG collection systems for over two decades, little information about their capture efficiency is available because LFG generation rates usually remain unknown. Therefore, in order to enhance the efficiency of CH4 capture and reduce fugitive emissions, it is critical to improve the design of LFG collection systems, properly determine LFG production rates, and quantify gas flow patterns within landfills. This is particularly important for landfills that are actively operated as bioreactors, since LFG production rates are typically higher due to rapid degradation of organic waste, or landfills with intermediate covers in which gas transport between the atmosphere and the landfill body readily occurs. This study explores methods that can improve operation of bioreactor landfills by reducing CH4 emissions and enhancing CH4 collection efficiency, and that can be used to estimate LFG generation rates and the distribution of gas flow parameters within waste.;This work began with the analysis of an innovative gas collection system -- a near-surface high permeability layer -- for enhancing LFG capture and reducing fugitive CH4 emissions. The high-permeability layer serves as a gas conductive layer uniformly distributing gas pressure, which extends the zone of influence of pumping wells. The gas collection system with a near-surface permeable layer was able to entrap LFG far from the well. The uniform pressure distribution above the permeable layer contributed to minimizing oxygen (O2) intrusion into the landfill and maximizing CH4 oxidation throughout the landfill soil cover, in addition to improving the CH4 capture efficiency and reducing fugitive CH 4 emissions. More importantly, the presence of a permeable layer resulted in near constant collection rates of biogas regardless of variations in heterogeneous landfill conditions, such as waste permeability. The near-surface permeable layer also reduced preferential gas flows through cracks in the cover material, resulting in minimal impact of surface cracking on CH4 emissions and O2 intrusion.;A second task was to investigate and advance the baro-pneumatic method, which is used to quantify CH4 generation rates and estimate the gas permeability field. The baro-pneumatic method was modified by incorporating an inverse modeling approach, the pilot point method, to improve the efficacy of the method in landfills with heterogeneous gas permeabilities. Based on synthetic exercises, the inverse model reproduced the spatial permeability distribution reasonably well using transient pressure changes in response to the withdrawal of LFG during pumping tests. The LFG production rate was also successfully estimated using data from baro-pneumatic tests. The LFG flow models were calibrated to the site-specific gas pressure data using the modified baro-pneumatic method. These models were able to provide excellent predictions of gas pressure distributions and flow patterns in heterogeneous landfills.
机译：垃圾填埋甲烷（CH4）是导致全球气候变化的有力温室气体，因此，应进行收集以减少温室气体的排放。收集的CH4也可以用作替代能源。为了控制垃圾填埋气体（LFG）的排放，已使用了各种设计的气体收集系统。但是，LFG回收系统的效率可能会成问题，特别是在安装最终垃圾掩埋场之前。此外，尽管LFG收集系统已广泛使用了二十多年，但由于LFG的产生率通常仍然未知，因此几乎没有关于其捕获效率的信息。因此，为了提高CH4的捕集效率并减少逃逸排放，至关重要的是改进LFG收集系统的设计，正确确定LFG的生产率以及量化垃圾填埋场中的气体流动模式。这对于积极充当生物反应器的垃圾填埋场特别重要，因为由于有机废弃物的快速降解，LFG的生产率通常较高，或者带有中间覆盖层的垃圾填埋场很容易在大气和垃圾填埋场之间发生气体传输。这项研究探索了可通过减少CH4排放并提高CH4收集效率来改善生物反应器垃圾填埋场运行的方法，并可用于估算LFG产生率和废物中气体流量参数的分布。创新的气体收集系统-近地表高渗透层-用于增强LFG捕集并减少CH4的散逸性。高渗透层用作均匀分布气体压力的气体传导层，其扩展了抽水井的影响范围。具有近表面可渗透层的气体收集系统能够将LFG截留在远离井的地方。渗透层上方的均匀压力分布有助于最大程度地减少氧气（O2）进入垃圾填埋场，并在整个垃圾填埋场土壤覆盖物中最大化CH4氧化，此外还提高了CH4的捕集效率并减少了逃逸的CH 4排放。更重要的是，无论异质垃圾填埋场条件如何变化（例如废物渗透率）如何，可渗透层的存在都会导致沼气的收集率接近恒定。近表面可渗透层还减少了通过覆盖材料中裂缝的优先气体流，从而将表面裂缝对CH4排放和O2侵入的影响降到最低。;第二个任务是研究和改进气压-气压方法，该方法用于量化CH4的产生速率并估算气体渗透率场。通过合并逆建模方法（先导点方法）对气压-气动方法进行了修改，以提高该方法在具有非均质透气性的垃圾填埋场中的有效性。在综合演练的基础上，逆模型利用瞬态压力变化响应抽水试验期间LFG的抽出，合理地再现了空间渗透率分布。 LFG的产生率也可以使用气压测试的数据成功估算。 LFG流量模型使用改进的气压-气压法校准为特定地点的气压数据。这些模型能够为非均质垃圾填埋场的气体压力分布和流动模式提供出色的预测。

著录项

  • 作者

    Jung, Yoojin.;

  • 作者单位

    University of Delaware.;

  • 授予单位 University of Delaware.;
  • 学科 Engineering Civil.;Engineering Environmental.
  • 学位 D.Eng.
  • 年度 2010
  • 页码 149 p.
  • 总页数 149
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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