Funded PhD Studentship: Circular production of phosphorous fertiliser, anaerobic digestate matrix effects on recovery efficacy

Agriculture & Environment

PhD Studentship: Circular production of phosphorous fertiliser – anaerobic digestate matrix effects on recovery efficacy

Start Date: 1st October 2024

Primary supervisor: Dr Marie Kirby, Harper Adams University

Project description

Introduction to research area

The application of animal slurries and anaerobic digestates to land to provide crop nutrients is facing ever increasing regulatory constraints influencing how they are stored and spread to land. These regulations are aimed to reduce emissions into the atmosphere (ammonia and nitrous oxide) and the oversupply of fertiliser nutrients to crops that can then leach into groundwater and watercourses (phosphorus and nitrate). As an alternative to slurries and digestates being applied to soil, artificial fertiliser can be used to supply crop nutrients. The manufacture of artificial fertilisers relies upon the mining of phosphorous ore and the extraction of nitrogen from the air. The manufacture and use of artificial fertilisers contribute 22% of agriculture’s carbon footprint (Menegat et al., 2021). Therefore, reducing artificial fertiliser use and increasing the use of organic fertilisers and recovered nutrients has the potential to help agriculture’s journey to net zero, generate new revenue streams to farmers through the sale of different nutrient components and provide further food and political security.

This research will extend some of the near-commercial phosphorus removal activities we have undertaken at HAU treating cattle slurry. This PhD will examine fundamental principles influencing phosphorus recovery from anaerobic digestates, utilising a range of different types of digestates to determine which factor(s) affect the extraction process by electrocoagulation. Understanding these more fundamental principles will allow the development of this technology to commercialisation for the anaerobic digestion (AD) industry. Currently there are 1,020 operating commercial AD plants in the UK (ADBA, 2024), with approximately 132,000 commercial AD plants globally (WBA, 2019). 

Furthermore, this project will undertake a Life Cycle Assessment (LCA) and Cost Benefit Analyses (CBA) to determine not only the economic, but also the wider environmental and societal cost impacts of utilising recovered phosphorus from digestates compared to using artificial fertilisers for crop growth. This wider societal impact is becoming increasingly important to agriculture as the wider impacts of farming are being discussed and financially supported to influence positive change. For example, farmers receiving funding to reduce their ammonia and phosphorus pollution contributions, improving biodiversity indicators and offering alternative employment to increase rural social sustainability. We are looking to recruit an innovative researcher that would like to influence real-world change and develop the required skills for a future research-orientated career.

Aims and objectives

The aim of this PhD studentship is to develop a novel technology relating to the removal and recovery of phosphorus from different anaerobic digestates using electrocoagulation for future commercial exploitation.

There are three main objectives of this studentship. First, to determine the factor(s) effecting phosphorus coagulation within different anaerobic digestates (year 1). Second, to understand how to optimise phosphorus recovery, either by varying the electrocoagulation process or the digestate composition (depending on the findings of objective one) (year 2). Third, the project will undertake a LCA and CBA of using recovered phosphorus from anaerobic digestates to offset artificial fertiliser use to inform future electrocoagulation commercialisation plans with a global context (year 3).

The PhD student will receive commercially relevant training suited to working as a career academic, a public sector/industry researcher, or an agri-tech entrepreneur. Through this project the PhD student will receive bespoke training and support as required in experimental and laboratory skills, economics, life cycle analysis and data analysis, as well as gaining practical experience in research and the development of a novel technology. Knowledge exchange will be through peer-review academic publications and industry engagement to achieve impact both nationally and internationally.

The multidisciplinary team

The appointed PhD student will become part of a multi-disciplinary team at Harper Adams University and will be supervised by Dr Marie Kirby. Dr Kirby is a biochemist who research interests relate to the integration of novel technologies that develop circular economies for a range of agricultural residues and by-products. Co-supervision at Harper Adams University is provided by Dr Simon Jeffery and Professor Karl Behrendt. Dr Jeffery is a microbial soil ecologist to understand how soil organisms drive soil processes and Professor Behrendt has over 20 years’ experience in agricultural and resource economics with specific expertise in bioeconomic modelling. Dr Duarte Tito will be the industrial advisor providing technology advice for nutrient recovery and reuse.

Successful candidates will receive a yearly stipend (paid monthly) set at the UKRI rate - for 2024/5 this will be £19,237. Harper Adams University is unfortunately unable to offer a fee waiver for international students applying and evidence of funding will be required for International Fee paying students to show they can cover the difference between the UK and international fees for the full four years - for the 2024/5 academic year this amount is £10,890.  However, scholarships maybe be available at the time of appointment to cover the difference between UK and International fees for the duration of the programme.  

Applicants must hold a minimum of a 2:1 or equivalent bachelor's degree in an appropriate subject /high grade point average bachelor's degree for international applicants or a 2.2 alongside a suitable Master's Degree. Potential for research based on alternative qualifications/experience as judged acceptable by the university, will be considered on a case by case basis.

Candidates are encouraged to contact Dr Marie Kirby to discuss the project before applying if they wish to.