Rice straw to Biogas (R2B)

南安普顿的研究旨在通过使用创新的预处理技术，评估厌氧联盟的营养需求，以及根据其配置和物理环境优化生物反应器，最大限度地利用稻草产生沼气。这项工作将建立在丰富但零散的知识基础上，这些知识代表了稻秆消化技术的最新水平。这表明机械预处理可能有效，尽管没有可靠的定量数据。将进行间歇式甲烷电位试验，以评估施用机械处理后秸秆的反应动力学。连枷磨机被认为是一种首选技术，因为它结构简单而坚固，不依赖于在稻草应用中迅速变钝的切割刀片，以及在发展中国家成功使用的历史，例如在茶叶行业。将其性能与锤式、球磨机等其它系统进行比较。在批量试验之后，将进行更广泛的试验，使用半连续进料消化器来确定特定和体积气体生产率以及消化器的运行稳定性。秸秆的成分分析不仅可以表明其理论甲烷潜力，还可以表明其营养价值和缓冲能力，作为选择性添加必需元素以提高沼气池性能的基础。半连续试验将在一系列负载条件下在中温和亲热温度下进行，并监测关键操作参数，以建立基线动力学数据，以便对中试工厂的性能进行比较和优化。现有技术还表明，稻草可能缺乏天然的pH缓冲，可以通过与动物浆液共消化来提高性能。迄今为止，工作主要集中在牛粪和猪粪上。计划中的工作还将考虑鸭粪和禽粪，因为这些在菲律宾和世界上其他广泛种植水稻的地区很容易获得。粉碎和粪肥添加都将显著改变基质的流变学，这将影响干消化系统的运行模式。因此，渗透性测试将在分批干消化过程的不同阶段进行。这将涉及运行模拟中试工厂的小规模“干式”消化器，并为规模因素的直接比较和评估提供数据。还将评估酸化倾向，并将考虑从渗滤液中回收第二级甲烷的潜在需求：如果有必要，可以通过与低技术含量的第二级反应器（例如厌氧过滤器）耦合来实现这一目标，并回收酸剥离液体以克服缓冲问题。其他控制措施，如干式消化器的批量排序和启动时底物与接种物比例的优化，也将作为操作策略的一部分进行评估，以匹配收获时间表并最大限度地减少储存要求。当渗透性是一个问题时，将使用惰性膨胀材料进行测试，以改善水力分布并减少短路。以前的工作表明，具有高固体含量的农业残留物需要很长的操作周期才能达到确定厌氧菌群的营养需求和消化特性所需的伪稳态条件。这为利用先进的显微镜、拉曼光谱和基因技术监测生物量特征和种群结构的变化提供了机会。至关重要的是稻秆能源生产系统的整体可持续性，实验室和试验工厂的数据将输入先前开发的能量平衡模型，为曼彻斯特团队的工作提供处理后的数据输出。

The research at Southampton seeks to maximise biogas from rice straw through the use of innovative pre-treatment techniques, evaluation of nutritional requirements of the anaerobic consortium, and optimisation of the bioreactor in terms of its configuration and physical environment. The work will build on the rich but fragmented knowledge which represents the state of the art in rice straw digestion. This suggests that mechanical pre-treatment may be effective, although reliable quantitative data are not available. Batch methane potential tests will be carried out to assess the reaction kinetics of the straw after the application of mechanical treatments. The flail mill is targeted as a preferred technology because of its simple and robust construction, lack of reliance on cutting blades that are rapidly blunted in rice straw applications, and history of successful use in developing countries e.g. in the tea industry. Its performance will be compared with that of other systems such as hammer and ball mills. The batch tests will be followed by more extensive trials using semi-continuous fed digesters to establish specific and volumetric gas productivities and digester operational stability. Compositional analysis of the straw will indicate not only of its theoretical methane potential but also its nutritional value and buffering capacity, as a basis for selective additions of essential elements to improve digester performance. The semi-continuous trials will be conducted at both mesophilic and thermophilic temperatures over a range of loading conditions, with monitoring of key operating parameters to establish baseline kinetic data against which pilot plant performance can be compared and optimised. Prior art also suggests that rice straw may be deficient in natural pH buffering and performance can be enhanced through co-digestion with animal slurries. To date, work has mainly focused on cattle and swine manures. The planned work will additionally consider duck and poultry manure, as these are readily available in the Philippines and other parts of the world where rice is extensively cultivated. Both shredding and manure addition will significantly alter the rheology of the substrate, which will impact on the operating mode of a dry digestion system. Permeability tests will therefore be conducted at various stages through the batch dry digestion process. This will involve running small-scale 'dry' digesters that simulate the pilot plant and provide data for direct comparison and assessment of factors of scale. The propensity for acidification will also be assessed, and the potential requirement for second-stage methane recovery from the leachate will be considered: if necessary this could be achieved by coupling to a low-tech second stage reactor (e.g. anaerobic filter) with recycling of acid-stripped liquid to overcome buffering issues. Other control measures, such as batch sequencing of the dry digesters and optimisation of the substrate-to-inoculum ratio at start-up, will also be evaluated as part of an operational strategy to match harvesting schedules and minimise storage requirements. Where permeability is an issue the use of inert bulking material will be tested to improve hydraulic distribution and reduce short circuiting. Previous work has shown that agricultural residues with a high solids content require long operating periods to reach the pseudo steady state conditions needed to determine the nutritional needs of the anaerobic consortia and the digestate properties. This provides the opportunity to monitor changes in biomass characteristics and population structure using advanced microscopy, Raman spectroscopy and gene techniques. Of key importance is the overall sustainability of the rice straw energy production system, and the laboratory and pilot plant data will feed into previously developed energy balance models to provide processed data output for the work of the Manchester team.