PhD spotlight: Mike Kelland's studentship, ' Experimental investigations of enhanced weathering as a geoengineering CO₂ removal strategy"

In the second our our series of PhD spotlight blogs, former PhD student, Mike Kelland, talks us through his experience. Mike's studentship was funded by NERC and was titled 'How to cool the planet and save coral reefs by 2100: Experimental investigations of enhanced weathering as a geoengineering CO₂ removal strategy'.

What made you decide to do a PhD?

I applied for the PhD because I was eager to take on a new challenge and delve deeper into research. During my previous studies, I discovered a passion for independent investigation and writing, but recognised the need to strengthen my practical skillset. The PhD offered a path to acquiring advanced skills through learning from and collaborating with established academics, while allowing me to focus on a research topic that I'm passionate about.

Tell us about your experience as a mature student

Starting the PhD in my mid-thirties meant balancing my studies with the responsibility to support my wife and three young children. It was tougher than I expected, but I was fortunate to receive tremendous support, advice and flexibility from my supervisors, university support staff, family and friends. Despite the age gap, I never felt socially isolated from my cohort, and instead found a strong sense of community through shared interests and a passion for learning. Being a mature student does have its advantages, though. For example, the project management and training skills I honed during my previous career in finance proved highly transferable to effective research planning and science communication.

Why did you choose a PhD in climate change mitigation?

My interest in climate change mitigation was piqued during my undergraduate studies in natural science. The future relevance of the topic became evident as I learned about the severity of anthropogenic climate change, and the need for both deep emissions cuts and technical solutions to rectify Earth's radiative energy balance. My dissertation research on solar radiation management approaches further solidified my interest, and I subsequently tailored my Earth Science Master's degree to focus on CO₂ removal strategies. Given this path, pursuing a PhD project related to climate change mitigation felt like a logical next step.

With that in mind, what led you specifically to the LC3M studentship over another choice?

The PhD project at the University of Sheffield aligned perfectly with my skillset, academic interests and desire to engage in practical research on CO₂ removal. The prospect of working with a multi-institution supervisory team, comprised of leading scientists with a broad range of expertise, further strengthened the project's appeal. Moreover, my previous research had identified ERW as a promising yet understudied strategy with significant potential for advancement, requiring an interdisciplinary approach that complemented my training.

What were the highs and lows of your PhD?

Overall, my PhD experience was thoroughly enjoyable, despite the inevitable challenges. The usual suspects – imposter syndrome, dealing with criticism and setbacks – all surfaced at some point, followed by unexpected disruption caused by the global pandemic. I loved the practical aspects of experimental research, but found thesis writing to be particularly challenging, partly due to the (largely self-imposed) pressure to create a highly-polished, lasting record of my contribution to the field, which could become overwhelming at times. Thankfully, with support from an amazing network of supervisors, colleagues, friends and family, I persevered. The highs easily outweighed the lows. From the thrill of conducting a successful experiment to the surreal yet equally exhilarating experience of seeing it broadcast on the 9 o'clock news, the research itself was incredibly rewarding. Being part of a team working towards meaningful scientific progress was a huge privilege.

What did your thesis, 'Enhanced weathering with crops in agricultural soils: quantifying basalt weathering rates, carbon capture and associated co-benefits for soil and yield improvements', find on ERW?

Many of the expected effects of applying crushed basalt to agricultural soil, such as increased soil pH and improved crop yields, were confirmed by the data obtained from my laboratory experiments. However, as is typical in experimental research, the most significant discovery emerged from results that diverged from expectations. Specifically, previous research suggested that the key evidence of rock weathering, notably the release of base cations during mineral dissolution, would be detectable in the water percolating out of soils treated with basaltic dust. However, this signal was not detected in any of my experiments. Instead, most of the base cations liberated by weathering processes were readily adsorbed onto soil cation exchange sites, with a small percentage assimilated into plant tissues. These results suggested the existence of time lags between mineral dissolution and cation export, which could affect the timescale for CO₂ removal via ERW. In short, while basaltic minerals appeared to dissolve as expected, the cations critical for carbon capture reactions weren't immediately released from the soil.

What are you doing now, and do you have any immediate career plans beyond that?

I’m currently employed as a postdoctoral researcher within the LC3M, and it’s a pleasure to continue working at the centre where I obtained my PhD. As I look towards the next phase of my career, the recent explosion of interest in ERW offers a wealth of exciting opportunities, both inside and outside of academia. My passion for empirical research naturally leads me towards continued involvement in experimentation. However, the emergence of a commercial ERW sector, alongside the development of new accreditation and standards organisations, presents a variety of compelling alternative paths where I could potentially apply my training. The next chapter is not yet written, but I'm looking forward to making further contributions to the field.

Any thoughts on the future of ERW?

In recent years, the focus of ERW has shifted rapidly from academic research to real-world deployment, with numerous for-profit companies now engaged in large-scale projects. However, significant hurdles must be overcome before ERW can be effectively utilised for climate change mitigation, notably with respect to the reliable and accurate quantification of CDR rates in open, real-world systems. Existing quantification methods are often expensive, labour-intensive and complex, highlighting the need for novel approaches and technological advancements. While geochemical models will likely be necessary to estimate CO₂ removal and reduce deployment costs, current models lack the sophistication needed to generate carbon credits, and so increased model complexity and further empirical testing is required.

With commercial entities already deploying ERW, robust standards are now urgently required to curb potential exploitation within carbon accounting systems. Environmental concerns associated with ERW deployment also warrant investigation, particularly the release of harmful trace metals during rock weathering and their broader impact on natural ecosystems. Additionally, the energy consumption and carbon emissions associated with large-scale rock crushing and transportation necessitate careful evaluation to ensure that ERW results in a truly positive net environmental impact.

While ERW holds significant potential, I believe that resolving these issues through further research, technological innovation and robust regulations is crucial for its successful and sustainable deployment.