Description of limit and failure states for biological methane oxidation in landfills: experimental investigation, chemical analysis, mechanical modeling and computational simulation

随着时间的推移，垃圾填埋场的有机成分被细菌活动转化。由此产生的填埋气体由40%的二氧化碳和60%的甲烷组成。如果没有安装收集系统，堆填区气体可以自由排放到大气中。不幸的是，甲烷是一种特别有害的温室气体，对大气的污染是二氧化碳的23倍以上。因此，政治、科学和工业界正在寻找技术，以永久减少甲烷排放。正常的程序是用所谓的威尔斯井主动抽取填埋气体，然后最终热处理气体。然而，由于细菌活动减少，天然气产量减少的时间仍然是一个未解决的问题。这个时间段被称为被动善后阶段，可以持续100年或更长时间，这带来了困境。一方面，在几十年的时间内积极提取填埋气体在财政上和技术上都非常昂贵。另一方面，堆填区气体对大气的长期污染是不负社会责任或不合理的。因此，需要一种解决方案，该解决方案i）导致合理的成本，ii）在技术上是可行的，并且iii）在故障或失效方面显示出足够的可靠性。关于前两个方面，甲烷氧化层似乎是一种有前途的解决方案。甲烷氧化的过程是基于甲烷氧化菌将从垃圾填埋场提取的甲烷转化为危害较小的二氧化碳和水。由此产生的问题是甲烷氧化层是否能够完全转化来自填埋场的进入气体。此外，该层的性能容易受到外部边界条件例如温度、基材含量、湿度或氧饱和度的影响。因此，本项目的目的是对甲烷氧化层中生物-化学耦合的扩散-对流-反应过程进行基础研究和预测。在研究项目的第一部分中，在正常条件下对模型和仿真方面的层的功能进行了实验分析。在该项目的第二部分，将对模型进行改进，使其也考虑到由于长期缺乏营养或极端炎热、寒冷、潮湿和干旱而出现的极限和故障状态。主要关注的是回答的问题是否以及以何种方式甲烷氧化层能够恢复后，这种极端的环境条件下，以及如何在接下来的时间内发展的层的性能。

Over time the organic components in landfills are converted by bacterial activities. The resulting landfill gas is composed of 40% carbon dioxide and 60% methane. If no collection system is installed, the landfill gas can freely emit into the atmosphere. Unfortunately, methane is an especially harmful greenhouse gas and pollutes the atmosphere over 23 times more than carbon dioxide. Therefore, politics, science and industry are searching for technologies in order to permanently reduce the methane emissions. The normal procedure is to actively extract the landfill gas with so called gas wells and then finally to dispose the gas thermally. However, an unsolved problem remains regarding the time from when the gas production decreases due to reduced bacterial activity.This time period is called passive after-care phase and can last for 100 years or more which presents a predicament. On the one hand, the active extraction of the landfill gas over a period decades is financially as well as technically very costly. On the other hand, the long term pollution of the atmosphere through the landfill gas is socially not responsible or justifiable. Thus, a solution is needed which i) leads to reasonable costs, ii) is technically feasible and iii) shows sufficient reliability in respect to malfunction or failure. Regarding the first two aspects the methane oxidation layer would appear to be a promising solution. The process of methane oxidation is based on the methanotrophic bacteria converting the extracted methane from the landfills into less harmful carbon dioxide and water. The question which arises is whether the methane oxidation layer is capable to entirely convert the incoming gas from the landfill or not. In addition, the performance of the layer can easily be influenced by outer boundary conditions for example temperature, content of substrate, humidity or oxygen saturation. Finally, this could even result in the complete failure of the methane oxidation layer.Therefore, the aim of the project is the fundamental investigation as well as the prediction of the biologically-chemically coupled diffusion-convection-reaction-process in methane oxidation layers. In the first part of the research project the function of the layer was experimentally analyzed under normal conditions with regard to model and simulation aspects. In the second part of the project the model will be enhanced so that it also takes the limit and failure states into account which occur due to long periods without nutrition or extreme heat, cold, clamminess and aridness. The main attention is paid to the answering of the question whether and in what manner methane oxidation layers are able to recover after such extreme environmental conditions and how the performance of the layer develops in the following period.