IAP-24-009

Rock, charcoal and compost: Investigating synergistic effects of enhanced rock weathering, biochar, and compost amendments for soil remediation and carbon sequestration.

Global declines in soil health, fertility and carbon sequestration potential are of substantial concern. The limits of increased agricultural performance through inorganic fertiliser and seed technologies are being reached, necessitating new approaches to feed an expanding global population. In addition, to give us a realistic chance of meeting international climate targets, reductions in greenhouse gas (GHG) emissions are needed, alongside a concerted effort to maximise carbon dioxide removal technologies.

Substantial previous work has gone into assessing the efficacy of various organic and non-traditional soil amendments, particularly composts, that provide a readily available source of labile organic material, and biochar, that provides long-term carbon burial, nutrient loss reductions, and potentially GHG emission reductions. More recently the addition of silicate rock dust to soils has been introduced as a potential management practice. This ‘enhanced rock weathering’ (ERW) is a geoengineering technique that enhances the natural mechanism of silicate weathering. This process produces carbonate (alongside other ionic constituents) that can then be precipitated in the oceans to be sequestered in long-term carbon sinks. ERW is estimated to be able to potentially sequester 1-2 billon tonnes of atmospheric CO2-C per year by 2100.

While our understanding of these amendments in isolation is continually and rapidly evolving, there has been little consideration of synergistic effects¬ – additive or potentially inhibitive – when these amendments are co-deployed. In theory, potentially negative aspects such as the addition of unwanted harmful ions such as heavy metals, often associated with ERW, may be mitigated by biochar through its ability to increase cation exchange capacity and / or increase plant growth and nutrient uptake rates. Biochar can also enable soil carbon sequestration via its stable organic carbon pool, while enhancing soil microbial activity and help create more suitable conditions for weathering processes.

The concurrent additions of compost, biochar and ERW strategies potentially provide a suite of improvements to soil health and do so without conflicting with the need for agricultural land use for food production. In this PhD we will quantify synergistic effects of these key soil amendments, allowing us to determine best practice for application to achieve various management improvement goals, including agronomic performance, soil heath and structure, soil organic matter concentration, and carbon sequestration. To achieve this, this project will address the following key objectives:

i) Elucidate the effects of amendment applications on soil structure, health, biogeochemical cycling and carbon sequestration potential.
ii) Examine the interactions between biochar, compost, and different rock sources with varying degradation and heavy metal contamination potentials (e.g., olivine in crushed dolerite vs. wollastonite or limestone).
iii) Quantify the impact of amendment formation process on functioning. For example, application of separately produced compost, rock and biochar vs. co-composted biochar, and biochar produced alongside rock.

This project will adopt a range of techniques to establish the key drivers and interactions of different soil amendments in agricultural systems. Quantifying and characterising aspects of soil structure, soil chemistry, nutrient stocks and fluxes, carbon cycle dynamics, and hydrology will enable this project to offer novel insight into the individual and synergistic effects an inform best management practices. To fulfil the stated objectives the student will use a combination of field and lab-based experiments, coupled to state-of-the-art sediment, gas, water and nutrient analytical techniques.

A potential timeline for research activities over the 3.5 years is given below, but there will be potential for the successful student to customise and adapt the project as it progresses.

Year 1

1. Literature review, research question exploration.
2. Establishment of mesocosm experiments (experiment 1) to explore objective 1.
3. Potential undertaking of field trial set-up.

Year 2

1. Ongoing measurements and wrap up of experiment 1.
2. Mesocosm experiment 2 to address objective 2.
3. Development of co-produced amendments for use in experiment 3.
4. Write up of experiment 1 and manuscript preparation.

Year 3

1. Utilise co-produced amendments to establish third mesocosm experiment to address objective 3.
2. Conduct final sampling of ongoing field trials established in year 1.
3. Write up of experiment 2 and manuscript preparation.

Year 3.5

1. Complete experiment 3.
2. Preparation of manuscript 3 and thesis production.
3. Viva preparation.

This project provides an excellent opportunity for training is state-of-the-art soil science, geochemistry, agronomic, and biogeochemistry techniques, equipping the successful candidate with a suite of techniques for multiple career opportunities.

The candidate will work closely with all four supervisors. In Glasgow, Dr Bass will oversee the project direction, development and overall progress of the candidate as well as providing training in all techniques and instrumentation available in the UofG carbon analytical suite. Dr MacDonald will provide input on experimental setup and soil/amendment characterisation pre- and post-experiment. From co-supervisors at Newcastle University, Dr Reershemius will provide input on quantification of carbon and other reaction product budgets and Dr Jayakumar will support on biochar production using locally available feedstock (miscanthus straw, wheat straw etc.) and subsequent characterisation to study structure-property relationships. The candidate will additionally have access to post-graduate training courses at the UoG as well as extensive IAPETUS DLA-cohort and NERC training workshops, allowing for a wealth of both specific and broader, transferable research skills and knowledge to be gained.

The candidate will join vibrant research communities at the University of Glasgow and at Newcastle University, where they will be welcomed and encouraged to network with colleagues and their collaborators. The candidate will have the opportunity to present their results to at least one national and two international research conferences. Furthermore, they will be encouraged to disseminate their results to the public at school and community events, and to share their findings with other research institutes and national networks.