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

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 compost
The 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.

In summary, this proposal aims to support the circular economy whereby waste materials, specifically food wastes are-purposed, re-used, or become feedstocks for other processes in order to create value from waste. It aims to exploit the new enabling features of microbubble AD to generate 100-110% more methane and then using microbubble mediated mineral carbonation to sweeten the biogas to sequester the CO2 and generate enriched CH4 which can be used for energy generation or stored and sent off to the electricity grid.

The exploitation path, however, for this proposal is tightly aligned to the endusers. The endusers would welcome the increase in the process efficiency and energy generation as well as a process that sequesters the CO2 whilst achieving the primary goals of the plant. The process integration achieves a reduction in OPEX due to the increase in CH4 production and the is only a significant increase in CAPEX. The co-product in this is a high quality manure making this process extremely beneficial and wide reaching in its impact to industry in a variety of sectors.

Perlemax are looking to exploit their IP around their patent portfolio, and catalyse the industrial early adoption of their technology for microbubble AD. This proposal is directed at the perceived barriers to commercialisation -- scale up and demonstration at sufficient scale to warrant industrial scale demonstration. CaCaCa and Perlemax would like to see the mineral carbonation operate onsite in order to establish key performance parameters with which they can be benchmarked with current technology. This technology can be used across a wide set of sectors and therefore wouldn't have many problems for the same.

The short term impact will be made with the commercial partners on the grant, but their commercial plans are to roll out the technology to endusers, but likely to license it to a service company for the waste management sector.