Dr Marie Kirby

Supervisor Details

Contact Details

Agriculture and Environment, Harper Adams University

Scientific Background

Research Interests

My research has focused upon integrating novel technologies (anaerobic digestion (AD) and intermediate pyrolysis) for the optimisation of energy production, waste/residue utilisation and reduction in greenhouse gas emissions. My recent research area has focused on the development of dry AD and nutrient recovery for the production of fertiliser-type products. Also, we have published some research investigating the survivability of pathogens and antibiotics through AD, prior to land application of the resulting digestate. With pyrolysis, my research interests are focused on utilising novel residues for pyrolysis and the subsequent uses of biochar for crop production and further nutrient recovery technologies.

My PhD investigated adapting current technologies from around the world for the novel purpose to dispose of fallen pig carcases on-farm. AD was investigated as an alternative method to try to alleviate the high cost, high carbon footprint and the biosecurity (pathogen) issues associated with current livestock disposal methods stipulated by EU legislation. Additionally, on behalf of the UK pig industry, I have undertaken further research to investigate the valorisation of pig carcase material through the use of on-farm refrigeration.

These research projects have been undertaken with a range of different companies, both via national and internationally funded research projects. Research grant funding has been kindly provided from a range of funders, for example EPSRC, Horizon 2020, Interreg, UK Department of Transport, AHDB, private companies etc. Some of the research has been undertaken directly with industry to ensure that project deliverables can be transformed into commercial practice.

Involved with these other projects (as researcher)

Supervision Style

In three words or phrases: Collaborative, supportive, outcome-oriented.

Provision of Teaching

I prefer to take responsibility for your technical training at first working amongst the wider research team, leading to more independence later. Training will be provided by our experienced research team and the wider scientific community at HAU.

Progression Monitoring and Management

I like to be kept up to date with the project’s progress, discussing your ideas and plans for the next stage of the project, whilst developing your required skillsets.

Communication

I am here for advice and guidance to help you reach the goals you set for yourself and the project. Communication forms will vary depending on the context, but will range from using Teams, emails, research team group chats, depending on the scenario.

PhD Students can expect scheduled meetings with me:

In a group meeting

At least once per fortnight

In year 1 of PhD study

At least once per fortnight

In year 2 of PhD study

At least once per month, or more often if they request it

In year 3 of PhD study

At least once per month, or more often if they request it

These meetings will be a mixture of face to face and video chat or telephone, and I am usually contactable for an instant response every working day.

Working Pattern

Certain tasks in my lab need to occur at set times, and students need to be able to commit to a rota/timetable shared with other members of the team. During periods of desk-study, more flexible working arrangements are possible but the student has to take responsibility for their work and ensuring this is completed in a timely fashion.

Notice Period for Feedback

I need at least 2 weeks' notice to provide feedback on written work of up to 5000 words.

MIBTP Project Details

Current Projects (2025-26)

Primary supervisor for:

Examination of intermediate compounds in anaerobic digestate and their effect on phosphorous removal using electrocoagulation

See the PhD Opportunities section to see if this project is currently open for applications via MIBTP.

Please Note: The main page lists projects via BBSRC Research Theme(s) quoted and then relevant Topic(s).

Examination of intermediate compounds in anaerobic digestate and their effect on phosphorous removal using electrocoagulation

Secondary Supervisor(s): Dr Simon Jeffery

University of Registration: Harper Adams University

BBSRC Research Themes: Renewable Resources and Clean Growth (Industrial Biotechnology)

Project Outline

Modern agriculture is required to produce ever increasing quantities of food, both for humans and livestock, from a reducing land area. Decades of intensive agriculture to meet the ever-increasing demand for food has led to soil degradation and reducing crop yields. To maximise crop production, agriculture relies on nutrient inputs, sourced from internationally traded artificially made fertilisers and through the re-use of locally available animal excreta (slurries and anaerobic digestates). The manufacture of artificial fertilisers requires a significant amount of fossil fuel, mined rock phosphorous and nitrogen removed from the air. Artificial fertilisers are moved across the globe to deliver crop nutrients, dramatically increasing the carbon footprint of the food we eat. Additionally, artificial fertilisers are commonly manufactured in politically unstable geographical regions, increasing food insecurity and economic costs. Their continued use is now considered unsustainable.

A considerable proportion of the phosphorous and nitrogen fertiliser nutrients applied to soils are captured in animal slurries, manures and anaerobic digestates. Legislation dictates when and how they can be applied to farmland to provide fertiliser nutrients for crop growth. Due to the high-water content of these slurries, their land application is time-consuming, increases soil compaction and if applied incorrectly, can result in leaching of nutrients into waterways causing eutrophication. Slurry and anaerobic digestates are typically applied to meet the crop's nitrogen requirement, causing an overapplication and accumulating of soil phosphorous, increasing soil erosion.

To reduce overapplication of phosphorous when animal slurries and anaerobic digestates are applied to soil, phosphorous can be removed prior to land application. Previous research at Harper Adams University has demonstrated that >98% of phosphorous can be removed and separated from cattle slurry and digestates using electrocoagulation technology (Reilly et al., 2021). A more recent study has demonstrated that this removed phosphorous from cattle slurry was bioavailable for crop uptake when applied to a grass crop (Innovate UK, FIP 10003082 Phosphate circularity: from dairy cow slurry to grassland agronomy, under publication), offsetting the need to use artificial fertilisers.

This project will develop this research further, concentrating on the phosphorous removal and reuse from a range of different anaerobic digestates. Due to the more complex bio-chemical composition of anaerobic digestates produced from different feedstocks, electrocoagulation could be a suitable technology for biochemical reduction in this product stream (Reilly et al., 2019). Understanding the bio-chemical interactions of differing anaerobic digestates on the performance of electrocoagulation, the subsequent speciation of phosphorous and its bioavailability for crop uptake are key discoveries required to achieve a ‘nutrient circular economy’ through extraction of phosphorous from renewable/sustainable sources (for example slurry and digestates).

References

M. Reilly, A. P. Cooley, B. Richardson, D. and M. K. Theodorou (2021). Electrocoagulation of food waste digestate and the suitability of recovered solids for application to agricultural land. J. Water Proc. Eng., 42: 102-121. https://doi.org/10.1016/j.jwpe.2021.102121

M. Reilly, A.P. Cooley, D. Tito, S. A. Tassou, M. K. Theodorou (2019). Electrocoagulation treatment of dairy processing and slaughterhouse wastewaters, Energy Procedia, 161, 343 – 351. https://doi.org/10.1016/j.egypro.2019.02.10

Biotechnological exploitation of gut microorganisms and lignocellulosic substrates

See the PhD Opportunities section to see if this project is currently open for applications via MIBTP.

Please Note: The main page lists projects via BBSRC Research Theme(s) quoted and then relevant Topic(s).

Biotechnological exploitation of gut microorganisms and lignocellulosic substrates

Secondary Supervisor(s): Professor Liam Sinclair, Emeritus Professor Michael Theodorou

University of Registration: Harper Adams University

BBSRC Research Themes:

Renewable Resources and Clean Growth (Bio-energy, Industrial Biotechnology)
Understanding the Rules of Life (Microbiology, Systems Biology)

Project Outline

References

Previous Projects (2024-25)

Primary supervisor for:

Examination of intermediate compounds in anaerobic digestate and their effect on phosphorous removal using electrocoagulation