The world is currently in a state of climate change crisis, due to the release of gases that harm the environment, known as greenhouse gases (GHG), primarily carbon dioxide (CO2) and methane (CH4). To address the climate crisis at the national level, the UK government has set a target called Net Zero, to eliminate all GHG emissions arising from UK-based production and consumption processes by the year 2050. Achieving Net Zero will require extended research into ready-to-use clean energy processes, such as anaerobic digestion (AD), especially within the transport sector; which is presently the largest single-source contributor to GHG emissions in the UK. AD involves the breakdown of organic materials in the absence of oxygen to produce gas (biogas) composed of 50-70% CH4 and 30-50% CO2 that is commonly used for electricity generation. However, only the CH4 fraction of biogas produces energy, hence, biogas can be upgraded to contain over 95% methane (biomethane), which will further reduce the GHG footprint from biogas use and also make it a suitable replacement for conventional transport fuel such as petrol and diesel. But, the common methods used to upgrade biogas to biomethane are often associated with high energy demand, additional waste generation and the potential release of the trapped CO2, which reduces the overall energy yield and GHG reduction potential of biomethane.
A novel alternative is to enhance a key reaction that occurs during AD, i.e - hydrogen (H2)/CO2 conversion to CH4 by the addition of H2 to the AD process, known as biomethanation. In-vessel biomethanation (in-situ biomethanation) for the production of high-grade CH4 is relatively underdeveloped for FW AD. From previous research, I developed evidence that in-situ biomethanation can be integrated into FW AD with the potential of generating up to 65% and 59% increases in energy returns on investment (EROI) and carbon savings respectively, compared to the common biogas upgrade methods. However, a major drawback with the integration of this technology is the source of H2. Water electrolysis using excess energy from other renewable sources such as wind and solar has been proposed as an ideal H2 source. Because of the distance between respective renewable energy installations, the transportation of surplus energy from the source of production to the AD plant is still a challenge. Presently, only 2 FW AD plants upgrade biogas to biomethane (by common methods) in the UK. With the BBSRC Discovery Fellowship, I can fully exploit the potentials of FW AD to produce high-grade biomethane as a replacement for vehicle fuels. The overall aim of this project is to recover high-grade biomethane from the AD of FW using integrated biological approaches that will achieve higher GHG savings, energy and economic returns on investment, and zero-waste production. The novelty of the proposed research includes the use of fungi to break down the difficult-to-digest fraction of FW to glucose, which will allow an enhanced production of H2 and the use of the H2 to support biogas upgrade to high-grade biomethane, thus, avoiding dependence on the common biogas upgrade methods or external H2 sources. The proposed research will also include a critical assessment of the water demand and use efficiency for FW AD plants in the UK. This project will include experimental, analytical and process modelling approaches to establish the potential for the commercial exploitation of the academic innovation developed at the University of Leeds by the industrial partner, Olleco.
This research meets the BBSRC remit requirement within the bioenergy strategic area, which focuses on using biological methods to generate new replacement fuels for a greener, sustainable future. It also aligns with a core component of the bio-economy, which involves the deployment of bioenergy within the UK with the potential to lead to job creation, economic growth, and enhance energy security.

Technical Abstract:
This project aims to recover biomethane (target-98%) from the anaerobic digestion (AD) of food waste (FW) using integrated biological approaches that will achieve higher GHG savings, energy and economic returns, and zero-waste production. The objectives are; (i) To investigate by the use of fungi, the biological transformation of cellulosic FW fractions to glucose for enhanced bioH2 recovery; (ii) To estimate by dynamic simulation the energy yield from an integrated FW-glucose-biohydrogen-biomethane nexus for industrial scale-up using Aspen Plus software; (iii) To close the FW AD water loop by the biological recovery of water from the digestate and recycling the same into the AD and (iv) To investigate by an environmental impact assessment, the potential for the commercial exploitation of the innovation. This research is structured within 4 work packages (WPs). WP1 involves the use of the design of experiment (DoE) to optimise glucose production from cellulosic FW fraction using fungi, followed by bioH2 production from the effluent by dark fermentation (DF). WP2 integrates bioH2 produced from WP1 with FW AD to facilitate H2/CO2 conversion to CH4 and will include a dynamic simulation of the process for industrial scale-up. WP3 involve investigations into biological methods for water recovery from the FW AD effluent that forms a holistic approach to achieving a circular economy during FW AD. WP4 will explore the route to market for the innovation through scale-up with the industrial partner, Olleco. This research meets the BBSRC remit requirement within the bioenergy strategic area, which seeks to generate new replacement fuels for a greener, sustainable future. Biomethane gives cleaner vehicle tailpipe emissions and receives twice the financial support by the renewable transport fuel obligation, which will influence the potential for immediate commercial exploitation of the research innovation and hence, the timely delivery of Net Zero targets in the UK.