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

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.

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.