phd project (refarm)

Unraveling phosphorus crystallization in animal manure: Defining mechanisms to innovate phosphorus recovery

Animal manure is the largest secondary source of phosphorus and contains significant amounts of nitrogen and potassium. The proper reuse of these nutrients is essential for increasing sustainability in agriculture. It will also play an important role in the energy transition, producing biogas and biomethane to achieve a reduction in fossil fuel consumption and CO2 emissions. The carbon returning to soil via land application can contribute to soil structure and strengthen soil health. A sustainable treatment of animal manure that can unlock the valorization of various resources will be of high societal relevance in the Netherlands and in the rest of the world.

At Wetsus, we developed resource recovery technologies that recover methane and phosphorus simultaneously during anaerobic digestion. These processes originated from source-separated wastewater treatment but recently were adapted to animal manure treatment. However, the mechanisms during animal manure treatment differ from those of wastewater treatment.

Research challenges
The complexity of the composition of animal manure made the recovery processes more challenging than those from wastewater. In previous research, phosphorus recovery could be achieved from manure, but the process required more steering through chemical addition than desired. We identified competition between cations, kinetics of precipitation and abundance of inorganic carbon, among others, as obstacles and hypothesized how they affect the recovery mechanism.

In the upcoming research, we are looking to dive into the crystallization mechanisms determining the formation and growth of precipitates to enhance the separation of nutrients. The mechanisms are determined by ion competition, the transformation of crystals, ion transport, and the conditions given by the surrounding biological treatment. Unraveling these mechanisms will guide the development of continuous treatment processes. Ultimately, the research challenge is the formation of easy-to-recover calcium phosphate crystals and granules under immense complex conditions with many interactions and parallel intrinsic equilibria.

Your assignment
You will combine your crystallization and (bio)reactor design knowledge to unravel the mechanisms of phosphorus precipitation and crystallization in animal manure. You will investigate the dissolution of preexisting precipitates and determine how calcium phosphate can be formed. You will translate your understanding of designs for resource recovery and work with colleagues to include your understanding in lab-, pilot- and demoscale processes. Your understanding of the mechanisms behind the formation of recovery products will further improve the recovery process. The implementation of your understanding in the ReFarM project will contribute to more sustainable agriculture. You will collaborate with stakeholders interested in the recovery of phosphorus and moving toward a more sustainable use of resources.

Your Profile
You hold an MSc degree in (geo)chemical or environmental engineering, biotechnology, geosciences, or similar studies, or you have a background in natural sciences but a strong affinity for engineering. Previous experiences with resource recovery processes are a plus, and mastering the German or Dutch language is a strong plus.

Keywords: (Bio)Crystallization, Calcium Phosphate, Process design, Biotechnology, Agriculture

Supervisory team: University promotor and co-promotor: Prof. Dr. Ir. Cees Buisman and Dr. Renata van der Weijden (Wageningen University, Environmental Technology),
Wetsus supervisor: Dr. Ir. Chris Schott

Only applications that are complete, in English, and submitted via the application webpage before the deadline will be considered eligible.

Guidelines for applicants:

Application form 2024.10: Unraveling phosphorus crystallization in animal manure: Defining mechanisms to innovate phosphorus recovery

  • You can only apply to one research project and indicate your second and third preferences (if applicable). Fill in the number (not the title) of the project, e.g., 2024.01
  • Fill in the number (not the title) of the project, e.g., 2024.01
  • Fill in the number (not the title) of the project, e.g., 2024.01
    i.e., in the first 4 years of your research career (full time equivalent) and not have a doctoral degree.
  • Drop files here or
    Max. file size: 20 MB, Max. files: 1.
      Upload your motivation letter (max 1 page), CV, copy of degree and grades and reference letter(s) as one PDF file. The PDF file must be named: (your first name) (your surname). Please refer to this guide for applicant for more details.