IAP-24-033

The impacts of gigaton-scale direct air capture of carbon dioxide on natural resources

Direct air capture (DAC) removes CO2 from the atmosphere using chemical sorbents in an engineered process. When coupled with geological CO2 storage (DACCS), a negative CO2 emissions technology is realised. DAC has been described as a “chemical separation to change the world”,[1] and its deployment at gigaton scale is a critical requirement in most internationally-agreed climate policy scenarios.[2]

The demands that gigaton-scale DAC will place on natural resources (e.g., land, water, and materials for construction and use as chemical sorbents) are poorly understood, as are the life cycle, environmental, and sustainability impacts. Moreover, different DAC technologies pose radically different demands on natural resources. For example, to capture 1% of annual global CO2 emissions, one incumbent technology will require ~20% of the global silica and ethanolamine markets,[3] and ~25% of global energy supplies by 2100.[4] This has prompted others to explore the use of natural minerals as sorbents instead, and powering DAC via photovoltaic energy combined with battery storage (which also requires minerals). Here, the environmental burden shifts dramatically to mineral resources depletion; such a process at gigaton scale would account for ~1% of all global annual environmental impacts.[5] In almost all DAC approaches, water is consumed in the synthesis and regeneration of chemical sorbents, and as an unintentionally co-captured species from air. Between 1 and 50 tons of water are consumed per ton of CO2 captured.[6] Thus, gigaton-scale DAC will also place very significant demands on water; developing ‘water management strategies’ is at the forefront of research in this area internationally.[6]

With a plethora of DAC technologies being proposed (>150 start-ups tracked by the US DoE), similar, yet distinct demands are expected to emerge for each technology. Thus far, life-cycle assessment (LCA) has focussed on individual DAC technologies, with very few comparative analyses. Moreover, as the technology matures and becomes more widespread there is a real need to quantify the demand on natural resources and particularly how these could compete with other climate interventions.

The overall methodology and timeline of the PhD will follow the stages of LCA; Goal & Scope Definition; Life Cycle Inventory; Comparative Life Cycle Assessment.

Year 1

Goal & Scope Definition: In Year 1, the student will perform a literature survey of DAC, ranging from incumbent technologies (TRL ~7-9) to start-ups (TRL ~5-6), and newly proposed approaches in the literature (TRL <5). Here, the primary aim is to identify a suitable number of case studies to describe the wide range of proposed approaches (and their resulting distinct economic, environmental, and resource demands). The student will set the objectives, assumptions, limitations, and boundaries of the LCA, to ensure that it is focused, relevant, and aligned with the intended knowledge outcomes. Here, the expertise of the supervisory team in terms of a broad overview of DAC,[7,8] the development of their own DAC technologies,[9] and relevant LCA’s,[7,10] will ensure the student is provided with world-class supervision.

Year 2

Life Cycle Inventory: In Year 2, the student will gather comprehensive data on all relevant inputs and outputs associated with the case studies selected in Year 1. This will cover resource extraction to disposal/recycling, including their transportation, packaging, and emissions resulting from these processes. The output will be a robust dataset that provides the foundation for the subsequent stages of the LCA. Here we will work with incumbent DAC technology providers that publish this data transparently (e.g., Climeworks) and our network which includes start-ups and academics developing new approaches to DAC.

Year 3

Comparative Life Cycle Assessment (LCA): In Year 3, the student will perform a comparative LCA on the case studies selected in Year 1, using the data gathered in Year 2. The magnitude of the impacts on various environmental categories will be assessed, e.g., global warming potential and resource depletion (land, water, materials etc), weighted against the positive impacts of DAC (based on their individual performance metrics, i.e., CO2 removal efficiency). Overall, the outcome will be a comprehensive assessment framework for DAC and several comparative LCAs, which can guide decision-making, policy, and future DAC technology development (i.e., provide a tool for multicriteria optimisation of DAC technologies in the context of natural resource depletion). During this time, the preparation of publications will begin.

Year 3.5

Interpretation of the results in a global context, writing of the PhD thesis, and publication of high-impact outputs.

In the first half of Year 1, the student will undergo a Training Needs Analysis, and draft their 3-month Research Project Proposal, with the supervisory team having oversight. The Training Needs Analysis will identify generic training that the student self-identifies as needed (e.g., presentation skills, working with your supervisors etc). These courses will be provided for free by Newcastle University. Moreover, the student will attend a “Responsible Research & Innovation and Ethics” training course delivered by the Inter-Disciplinary Ethics Applied Centre (University of Leeds). This is a paid course (see Training Component of RTSG). Together, these will provide the student with the generic skills needed to complete a PhD, as well as a strong grounding in responsible research.

In the second half of Year 1, the student will attend a week-long training course “Sustainability-Ready Engineers” which focusses on life-cycle assessment (LCA) and techno-economic assessment (TEA), delivered by Green Rose Chemistry, Centre for Process Innovation, and Northumbrian Water Limited, and a two-day “Data Science” training course delivered by the Mathematics, Statistics, and Physics department at Newcastle University. The first of these is a paid course (see Training Component of RTSG), whereas the second will be provided for free by Newcastle University. Together, these courses will provide the student with the specific technical, data, and modelling skills needed for the project. The student will also submit a Progression Report and undergo a Viva.

In Year 2, the focus will shift to research (data collection, methodology development etc) as the primary aim. However, the student will attend two international conferences towards the end of Year 2 to present their work (see Training Component of RTSG). This will provide the student with exposure to current research, networking opportunities, and build their confidence as they become an independent researcher. The student will be supported by the supervisors to apply for travel bursaries to attend further conferences/policy placements if they wish, and to present at public-facing, engagement events. This will provide the student with skills in applying for research funding and communicating with the public. The student will also submit a Progression Report and undergo a Viva.

In Year 3, the focus will shift to finalising modelling/results and writing of the thesis, whilst the training focusses on careers, professionalism, and ‘beyond the PhD’. The student will attend a “Career Transitions” course at Newcastle University, developed as part of the Process Industries: Net Zero (PINZ) CDT, where industry and academic leaders host ‘fireside chats’ with late-stage PhD students, advising them on their options and strategies to pursue their career aspirations. Also, the student will attend a “Research with Impact” course, which involves tailored support to publish outcomes from the PhD in journals of the highest standing/impact. These courses are also provided by the PINZ CDT (all will be provided for free). Finally, the student will be supported to begin their application for chartership of an appropriate professional organisation. The student will also submit a Progression Report and a Thesis Plan.