Enhancing the Methane Generation from Food Waste Anaerobic Digestion Mediated by Fluidic Oscillator Generated Microbubbles

作为一个文明社会，我们每年产生的食物垃圾数量巨大，超过20亿吨，如果处理得当，其中大部分可以以可持续的方式利用AD作为能源。以英国为首的欧盟每年产生超过8900万吨的食物浪费。作为第一步，这些废物可以作为动物的食物来源重新分配，但由于这种方法失败，最好使用AD来回收能量。根据2015年上议院关于食物浪费的报告中讨论的废物食物等级规定，AD代表营养回收，是所有其他废物管理方法的首选方案。AD是一种在无氧（无空气）条件下通过将高链化合物分解成甲烷和其他低链化合物，将食物垃圾、生物质或粪便转化为厌氧（无空气）的过程。这个过程通常遵循以下步骤- 1。将生物质（湿食物垃圾）放入密封的气密容器中。利用系统中存在的厌氧微生物消化这种生物质（湿食物垃圾），产生富含甲烷的沼气，用于发电3。作为粪肥或堆肥的消化液我们提出的途径是将密闭容器替换为利用CaCaCa工艺[1]和微泡技术对烟气进行现场脱硫获得的富CO2流态振荡微泡[2-5]。与常规工艺相比，定期注入（5分钟）富含CO2的微气泡可使CH4产量增加110%。这是一个双管齐下的过程，通过微泡剥离和同时注入营养物质来去除代谢物/废物。产生的甲烷可以用于发电，从而抵消化石燃料的使用，减少温室气体（GHG）排放。为了捕获CH4，我们使用CaCaCa工艺使沼气变甜，从而得到富含二氧化碳的微气泡，CH4随后被燃烧，烟气中含有丰富的二氧化碳（可能含有容易凝结的水蒸气）。这是进一步的自我维持，因为在第一步中产生的CH4燃烧导致产生烟道气。用于微泡生成的流体振荡器支持增甜和产甲烷（在AD中产生甲烷的过程）。这大大增加了在AD中形成的产品的价值，同时消耗了产生的二氧化碳，从而进一步抵消了温室气体排放。从这个过程中回收的热量增加了这种能量平衡，可以通过热电联产（CHP）用于现场供暖。该项目将对这种新型流体振荡富二氧化碳微泡工艺的现场原型进行研究，该工艺用于AD，并使用经过Perlemax流体振荡驱动微泡优化的CaCaCa工艺产生的烟气同时脱硫。如附录b第2部分所述，可以通过优化过程变量进一步增加CHP和CH4的生成。这可能会使CH4的生成量比预期的增加110%。这确保了碳足迹的最小化，同时最大限度地提高了产生的能量。在没有补贴或关税扭曲市场的情况下，这些潜在利益的结合可能是经济的。

As a civilisation, we generate an enormous amount of food waste with over 2 billion tonnes produced per year, much of which can be utilised as energy using AD in a sustainable manner if properly processed. The EU, with UK being the leading offender, generates over 89 MT of food waste per year. This waste can be redistributed as food source for animals as a first step, but with that failing, it is better to recover the energy using AD. AD represents nutrient recovery and is a preferred option over all other means of waste management as prescribed by the Waste Food Hierarchy discussed in the 2015 House of Lords report on food waste. AD is a process which converts food waste or biomass or manure in anaerobic (without presence of air) conditions by the breakdown of higher chain compounds into methane and other lower chain compounds. This process conventionally follows the following steps - 1. Placing biomass (wet food waste) into sealed air tight container 2. Digestion of this biomass(wet food waste) using anaerobic microbes present in the system to produce methane rich biogas to be used for energy generation 3. Digestate to be used as manure or compostThe pathway we are proposing is replacing the airtight container with fluidically oscillated CO2 rich microbubbles obtained by sweetening of the flue gas on-site using CaCaCa process[1] and microbubble technology[2-5]. Periodic injection (5 minute) of CO2 rich microbubbles has shown to increase CH4 production by 110% as compared to the conventional process. This is a dual pronged process with removal of metabolites/wastes by microbubble stripping and simultaneous nutrient injection. The CH4 generated can be used for energy generation thereby offsetting fossil fuel use and reduce Greenhouse Gas (GHG) Emissions . We get the CO2 rich microbubbles by sweetening biogas gas using the CaCaCa process in order to capture the CH4 which is then burnt and the flue gas is CO2 rich (potentially with water vapour which can be easily condensed. This is further self sustaining since the burning of the CH4 produced in the first step leads to flue gas generation. The fluidic oscillator for microbubble generation underpins the sweetening and methanogenesis (the process in AD wherein methane is generated). This greatly increases the value of products formed in AD whilst consuming the CO2 generated thereby further offsetting GHG emissions. Recovering the heat from the process add to this energy balance which can be used for on-site heating via Combined Heat and Power (CHP). The project is going to investigate the onsite prototype build of this novel fluidically oscillated CO2 rich microbubble process for AD and simultaneous sweetening of the flue gas generated using the CaCaCa process optimised with Perlemax's fluidic oscillator driven microbubbles. The CHP and CH4 generation can be further increased by optimisation of the process variables as discussed in AppendixB part 2. This would possibly increase CH4 generation over the slated 110%. This ensures a minimisation of the carbon footprint whilst maximisation of the energy generated for the same. The combination of these potential benefits could be economic without subsidy or tariff skewing the market.