Rice straw to Biogas (R2B)

南安普顿的这项研究试图通过使用创新的前处理技术、评估厌氧联合体的营养需求以及优化生物反应器的配置和物理环境来最大限度地利用稻草产生的沼气。这项工作将建立在丰富但支离破碎的知识基础上，这些知识代表了稻草消化的最新技术。这表明机械前处理可能是有效的，尽管没有可靠的定量数据可用。将进行批量甲烷势测试，以评估应用机械处理后的秸秆的反应动力学。连杆式碾碎机被视为首选技术，因为它的结构简单而坚固，不依赖于在稻草应用中迅速钝化的切割刀片，以及在发展中国家成功使用的历史，例如在茶叶行业。它的性能将与锤式和球磨机等其他系统进行比较。在批量测试之后，将使用半连续进料消化器进行更广泛的试验，以确定比容气体生产能力和消化器的运行稳定性。对秸秆的成分分析不仅表明其理论甲烷潜力，而且还表明其营养价值和缓冲能力，作为选择性添加必需元素以改善消化器性能的基础。半连续试验将在一系列加载条件下在中温和高温下进行，并对关键操作参数进行监测，以建立基准动力学数据，以便与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。到目前为止，工作主要集中在牛和猪粪上。计划中的工作还将考虑鸭粪和家禽粪便，因为在菲律宾和世界上广泛种植水稻的其他地区很容易获得这些粪便。粉碎和添加粪便都会显著改变基质的流变性，这将影响干式消化系统的运行模式。因此，渗透性测试将通过间歇干消化过程在不同阶段进行。这将包括运行模拟试点工厂的小规模“干式”消化器，并为直接比较和评估规模因素提供数据。还将评估酸化倾向，并将考虑从渗滤液中回收第二阶段甲烷的潜在要求：如有必要，可通过连接技术较低的第二阶段反应器(如厌氧过滤器)来实现这一点，并回收酸析出液，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优化底物与接种物的比例，也将作为操作战略的一部分进行评估，以匹配收获计划并将存储要求降至最低。在渗透性有问题的地方，将测试惰性膨胀材料的使用，以改善水力分配和减少短路。以前的工作表明，高固形物含量的农业残留物需要很长的运行时间才能达到确定厌氧联合体的营养需求和秸秆特性所需的准稳态条件。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。关键是稻草能源生产系统的整体可持续性，实验室和试点工厂的数据将输入到之前开发的能量平衡模型中，为曼彻斯特团队的工作提供经过处理的数据输出。

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.