(2025-OU5) Microbial origins of methane emissions and uptake in forested closed landfills

Landfills are the third largest source of anthropogenic methane, a potent greenhouse gas that contributes to global climate change. In the UK, remediation of former landfills commonly involves creating forested areas. There is evidence that trees growing on closed landfills can contribute to methane emissions (Fraser-McDonald et al., 2022). However, the origin of these emissions is still somewhat uncertain.  

In forested wetland ecosystems, which serve as natural analogues to managed landfill environments, complex relationships between communities of microbes influence the production and consumption of methane. For example, studies have identified bacteria within tree stems that reduce methane emissions (Jeffrey et al., 2021). Identifying the microbial populations present in forested landfill sites and their dynamics with trees growing in these environments will aid in pinpointing sources and sinks of methane. Understanding these dynamics will inform UK strategies aimed at mitigating emissions, tackling climate change, and supporting United Nations Sustainable Development Goals (UNSDGs), specifically Goal 13 (Climate Action), Goal 15 (Life on Land), and Goal 12 (Responsible Consumption and Production). 

This project aims to address this gap by investigating the influence of tree planting on microbial communities and associated methane emissions or uptake from forested landfills. The project will focus on a multi-faceted approach, combining fieldwork, process-based measurements, laboratory experiments, and microbial analysis to comprehensively understand methane cycling in these environments. Underlying mechanisms will be explored by sequencing microbial communities in the soils, plant rhizospheres, and tree stems to identify the presence and abundance of key methane-cycling microorganisms, such as methanogens (methane producers) and methanotrophs (methane consumers) ​(Macey, 2024; Macey et al., 2020)​. By comparing these communities in forested and non-forested landfill sites, the project will determine how tree planting influences microbial diversity and activity, and therefore methane fluxes. Additionally, laboratory experiments will provide insights into the metabolic pathways and conditions that promote either methane production or consumption, helping to identify the factors that could be manipulated to reduce emissions. 

Overall, this project aims to contribute valuable knowledge to the field of landfill management and climate change mitigation, supporting the UK’s efforts to reduce greenhouse gas emissions and align with the UNSDGs. 

Project highlights

• Locating the microbial origins of methane fluxes in forested closed landfill sites. 
• Isolating and characterising novel methane-cycling microbes. 
• Training in state-of-the-art techniques across the fields of environmental science, microbiology, and bioinformatics. 

Methodology

Process-based measurements using cavity ring-down laser spectroscopy will be conducted in a diverse range of landfill sites to quantify methane emissions and uptake. A combination of cultivation dependant and independent techniques will be applied to investigate the role of methane oxidation and production in the soils and plants of landfill environments. This will involve extracting DNA and RNA from environmental samples collected from landfill soils across the UK and identifying: 1) the diversity of methane-cyclers within the landfill and 2) comparing the methane-relevant microbes between the components of the soil, plants, and the different landfill sites. This will be supported by cultivation experiments to enrich and isolate the methane-utilisers identified within these environments, and analytical techniques to understand the environmental context of the samples (gas chromatography and mass spectrometry). The student will have access to a range of additional techniques at the partner organisations. 

Training and skills

DRs will be awarded CENTA Training Credits (CTCs) for participation in CENTA-provided and ‘free choice’ external training. One CTC can be earned per 3 hours training, and DRs must accrue 100 CTCs across the three and a half years of their PhD.  

The student will be trained in specific, field and laboratory-based techniques (cavity ring-down laser spectroscopy, gas chromatography, DNA extraction, and PCR), analytical geochemistry and culture-based microbiology by members of the research team. Short placements with the project partners will enable access to laboratory facilities and training in specific laboratory techniques. The student will also be trained in computer-based techniques. 

The student will benefit from additional skills development opportunities offered by the research groups within E&I and EEES, e.g., communication skills, time management, academic writing and more. The student will also develop skills in statistical analysis and presentation of quantitative data. 

Partners and collaboration

Dr Susheel Bhanu Busi (CEH) is a molecular ecologist with extensive expertise in microbial ecology, cell fluorimetry and metagenomic analysis of complex environmental samples. He will provide training and supervision in these specialised techniques as well project guidance via supervisory meetings. 

Dr Nia Jones (DEFRA) is a Senior Scientist in Resources and Waste where she leads on Net Zero Science. She is responsible for a multi-million-pound research portfolio on landfill emissions with previous research experience in computational pollutant modelling. She will provide expertise on the research’s statutory context and encourage real world impact. 

Further details

For further information, please contact [Email Address Removed].  

To apply to this project:  

• You must include a CENTA studentship application form, downloadable from: CENTA Studentship Application Form 2025.  
• You must include a CV with the names of at least two referees (preferably three) who can comment on your academic abilities.  
• Your application materials, including the CENTA Studentship Application Form 2025, your CV and the Open University application form must be emailed to [Email Address Removed]. Instructions on how to apply to the Open University are to be found on https://www5.open.ac.uk/stem/environment-earth-ecosystem-sciences/research/phd-students/current-opportunities-and-how-apply, please ensure you read this webpage before applying as you will need to obtain the relevant OU application form from here. Please quote CENTA 2025-OU5 when completing the application form. 

Applications must be submitted by 23:59 GMT on Wednesday 8th January 2025.