Ochres, aggregates and carbon sequestration - can geoengineering save the planet?

A field of bare soil, showing ploughed furrows

Image CC0 via pxhere

This project  will investigate using ochres as soil amendments to enhance the ability of soil aggregates to lock up carbon.

The studentship is part of the ACCE Doctoral Training Partnership, funded by NERC and starts October 2020.

Apply for this course

Read the eligibility criteria and application guidance below, then apply through the University of York's online application service.

Application deadline: 8 January 2020


Carbon dioxide is building up in the atmosphere and heating up our planet. The sustainable solution to minimise societal and environmental damage that global warming is causing is to transition to carbon neutral lifestyles. However, this will take time.

Geoengineering (intervening in the Earth’s natural systems to counteract climate change) is an approach that can buy us the time we need to make the transition. This project is about geoengineering.

Soils are a major carbon reservoir. Arable soils are typically depleted in carbon and changes in management practise, such as moving to minimum tillage systems, can help replenish their carbon stocks. However, there are biological and chemical constraints that limit the amount of carbon that soils can hold.

Project Aims

This project investigates manipulating soil chemistry in arable soils to enhance their carbon storage potential and thus enhance their role in limiting atmospheric carbon dioxide accumulation and restricting global warming.

Carbon is 'locked' into soils when it is incorporated into microaggregates. Iron oxides can be a limiting factor in the formation of microaggregates. Ochres are iron oxides deposits that precipitate in drainage waters of abandoned coal mines. The UK has no developed market for ochres and much energy and money is spent on their disposal to landfill. The chemistry and mineralogy of ochres is highly varied.

This project will investigate using ochres as soil amendments to increase the aggregate forming capacity of soils, enhancing their ability to lock up more carbon. The research could potentially deliver twin benefits:

  1. Buying society time to transition to a low carbon economy.
  2. Generating a market for ochres which typically accumulate at sites in economically depressed former mining communities.


Soils and ochres have varying compositions. Before you add anything to agricultural soil you must be sure that it will not impact on soil fertility or cause pollution problems. Therefore in this project you will:

  1. Collect ochres and characterise their chemistry and mineralogy.
  2. Collect and characterise arable soils of varying properties.
  3. Conduct adsorption, incubation and plant growth experiments to measure impacts of ochre amendments on soil carbon dynamics, microbial activity and plant growth and health.
  4. Produce an empirical model that predicts the potential for ochre amendments to increase soil-based carbon sequestration on the basis of ochre and soil properties.


The project is suited to Earth Scientists / Environmental Scientists / Physical Geographers and Chemists with an interest in soil chemistry and mineralogy.

Students with, or expecting to gain, at least an Upper Second Class Honours degree, or equivalent, are invited to apply. 

For informal discussion please contact the main supervisor Prof Mark Hodson.

ACCE studentships are available to UK and EU applicants only.

Residency rules apply. UK and EU students with qualifying residence in the UK are eligible for full-cost awards. Non-UK students from the EU who do not have qualifying residence are eligible for fees-only awards, which covers the tuition fees and Research Training Support Grant (RTSG), but not stipend. 

All applicants need to comply with the registered university's English-language requirements.

How to apply

Applications for the PhD are processed though the University of York's online application service. More information on the application process and the documents you need to provide can be found on the university's Department of Environment and Geography webpages.

The deadline for applications is 8 January 2020. 

Any questions?

If you have any questions about the project please contact

Main supervisor: Prof Mark Hodson


University of York

Main supervisor: Prof Mark Hodson

The Natural History Museum

Co-supervisor: Dr Paul Schofield

ACCE Doctoral Training Partnership

Joint PhD training partnerships between the Natural History Museum and the Universities of Sheffield, Liverpool and York, and the NERC’s Centre for Ecology and Hydrology (CEH).

Funded by