Increasing methane productivity in anaerobic digesters by addition of CO2

该项目的主要目标是确定在厌氧消化过程中添加二氧化碳导致甲烷生成增加的机制。虽然各种研究已经提供了足够的证据来证明这一效应，但到目前为止，其潜在的机制还只是假设，还远未被理解。为了再现这种效应并利用这种从废物中产生能源的巨大潜力，必须充分揭示这些机制。为了实现上述目标，需要采取跨学科的办法，包括使用稳定同位素方法作为工艺鉴定的关键参数，工艺工程的专门知识，包括提供设备齐全的实验室，具备进行连续流动试验的专门知识，以及伴随的微生物分析。为了确定详细描述的观察到的生物转化的基本机制，我们的目标是在TUM建立两个连续的厌氧消化测试系统。一个系统富含二氧化碳，而另一个系统作为对照。这些反应堆将使用污水污泥，因为它似乎是二氧化碳浓缩潜力最大的底物。试验将在不同的加载速率下进行，表明不同的应力状态可能对CH4-的形成机制产生重大影响。在试验期间，将监测标准工艺参数(TS、VS、COD、VFA、碱度、pH值、气量和质量)。此外，将通过最先进的分子生物学方法，如行业特有的DNA和mRNA水平的实时定量聚合酶链式反应和群落测序方法来表征数字遗产中的生物群落症。作为该项目的一个特别重点，为了将二氧化碳转化为甲烷，将在消化测试中应用包括同位素标记实验在内的同位素技术。有了这项强大的技术，就有可能重建二氧化碳添加过程中的前体和特定的路径。一旦了解了潜在的机制，就为该方法在实践中的实施提供了基础。

The major goal of this project is the identification of the mechanisms leading to increased CH4 formation by the addition of CO2 during anaerobic digestion. While enough evidence of the effect has already been provided by various studies, the underlying mechanisms have only been hypothesized so far and are still far from being understood. In order to reproduce the effects and to utilize this great potential for energy production from waste streams, the mechanisms had to be fully uncovered. To achieve the above mentioned goals an interdisciplinary approach is required including the use of stable isotope methods as the key parameter for process identification, know-how of process engineering including the supply of a fully-equipped laboratory with expertise in the performance of continuous flow-through experiments, and accompanying microbial analyses. To identify the basic mechanisms of the observed bioconversion described in detail, we aim at establishing two continuous anaerobic digestion test systems at TUM. One system is enriched with CO2 while the other serves as the control. The reactors will be fed with sewage sludge, since it seems to be the substrate with the highest potential for CO2 enrichment. Tests will be carried out at various loading rates indicating different stress regimes which might have a significant influence on the mechanism of CH4-formation. During the tests, standard process parameters (TS, VS, COD, VFA, Alkalinity, pH value, gas quantity and quality) will be monitored. Additionally, the biocenosis in the digestate will be characterized by state-of-the-art molecular biological methods such as guild-specific quantitative real-time PCR on DNA and mRNA levels, and community sequencing approaches.As a special focus of the project, in order to retrace CO2 conversion to CH4, isotope techniques including isotope labeling experiments will be applied during the digestion tests. With this powerful technique it is possible to reconstruct precursors and specific pathways during CO2 addition.Once the underlying mechanisms are understood, the basis for implementing the approach in practice is provided.