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Can trees be made ‘greener’? Mitigating methane emissions from forestry and bio-energy plantations using synthetic microbial communities

Principal Supervisor: Professor Vincent Gauci

Co-supervisor: Graeme Kettles

PhD project title: Can trees be made ‘greener’? Mitigating methane emissions from forestry and bio-energy plantations using synthetic microbial communities

University of Registration: University of Birmingham

Project outline:

This proposal seeks to explore potential ways pioneering tree methane emission work on natural ecosystems can translate into applications that may benefit both the UK forestry and bioenergy industries. The project will apply a novel mix of ecosystem biosphere-atmosphere exchange, microbial ecology and industrial forestry expertise to understand and mitigate emissions of methane from forestry and bio-energy trees while developing applications to enhance drawdown of powerful greenhouse gases.

Methane is a powerful greenhouse gas second only to carbon dioxide in influencing Earth’s climate. In this project the student will examine methane emissions from trees grown for forestry timber, bio-energy with carbon capture and storage (BECCS) and short rotation coppicing for bio-energy and examine novel mitigation strategies. In recent decades there has been growing interest in the use of bioenergy tree crops as alternative energy sources to fossil fuels in order to reduce greenhouse gas (GHG) emissions. The EU, for example, is committed to increasing the percentage of energy from renewable sources to 20% of total energy consumption by 2020 (EU, 2009) and, under the Climate Change Act 2008 (Great Britain, 2008), the UK government is committed to GHG emission reduction of 80% by 2050 cf. 1990 levels. The use of bio-energy could contribute to this target through plantations of trees, which include short rotation coppice (SRC) of willow and poplar. Further, BECCS is gaining increasing attention as an atmospheric CO2 removal strategy and this similarly requires tree growth. However, land-use change to accommodate plantations of SRC willow and poplar places bio-energy in direct conflict with food production and so can adversely affect UK and EU food security when there is an increasing demand. As a result of this land use conflict, plantations for bio-energy are increasingly being planted in so-called ‘marginal lands’ (Gelfand et al 2013, Nature) that have limited agricultural value often due to their high soil moisture status and tendency to flood. Both poplar and willow are highly adapted to wet conditions however work by this group and others has shown that, as a consequence of flood tolerance, such trees emit the powerful greenhouse gas methane that has been produced in the wet soil. Further, forestry for timber production is a major land use in the UK and across Europe but recent research has shown that even trees growing in usually free-draining soils can emit the powerful greenhouse gases methane and N2O from their stem bases (Welch et al 2019 GCB) which may diminish the net ‘climate good’ of trees. 

For BECCS and bio-energy forestry, methane emissions would reduce the efficacy of trees as a carbon neutral or carbon negative alternative to fossil fuel use thereby limiting their value as part of the GHG mitigation mix. In this project, the student will quantify methane and N2O exchanges in trees planted under wet and dry soil conditions to assess the role of forestry and plantation hydrology on trace GHG exchanges. Further the student will explore the potential to mitigate emissions of methane from tree stems using novel soil-derived amendments that both promote the establishment of ‘cryptogamic covers’ on trees (crusts of cyanobacteria, algae, fungi, lichens and bryophytes that establish on tree stems) that may host beneficial microbes that consume methane when applied to the stems, the principal egress pathway for soil-derived methane. In doing so we may characterise mechanisms to both mitigate any emissions from forestry, while potentially identifying a means to enhance atmospheric methane drawdown in all forests, to the overall benefit of Earth’s climate.

Methanotrophs are ubiquitous in free-draining soils so we shall analyse local soils for so-called ‘high affinity methanotrophs’ which are ideally suited to consuming methane at the relatively low concentrations encountered at the tree stem-atmosphere interface. It will also be possible to probe the methanotroph population already inhabiting the tree stem surface on these trees. From these soil and tree stem samples we will develop synthetic microbial communities containing methanotrophic soil derivatives which can be applied to the stem surface in spray form.

BBSRC Strategic Research Priority: Sustainable Agriculture and Food,: Plant and Crop Science

Techniques that will be undertaken during the project:

The student will work in both Prof Gauci’s and Dr Kettles’ laboratories.

The student will gain experience in microbial ecology and in the in vitro growth, culture and manipulation of natural microbial communities. This will include community analysis by high-throughput sequencing techniques. The student will also gain experience in laser gas analysis to understand biosphere/atmosphere exchange of powerful greenhouse gases at the tree stem scale.

Contact: Professor Vincent Gauci, University of Birmingham