Why is this research needed?

The growing urgency to address climate change accelerates worldwide CCS development. In addition to a massive reduction in CO2 emissions, the importance of negative emissions of CO2 cannot be overstated. Direct air capture (DAC) system aims to extract CO2 directly from the ambient air, and it is generally coupled with permanent geological storage or utilised in the production of fuels, chemicals, and other materials. The UK has set an ambitious target to deploy at least 5 Mt CO2 per year through engineered removals by 2030 [1]. With the rapidly evolving potential for scaling up engineered removals, DAC has been proposed to be developed and scaled up over next decades, contributing significantly towards achieving the net-zero emissions targets.

Liquid solvent-based DAC (L-DAC) as one of the most advanced and commercial DAC technologies faces challenges in high temperature heat and energy demand for regeneration process. To avoid compromised carbon reduction efficiency of DAC due to use of fossil fuels for generating requisite heat and electricity, solid oxide fuel cell (SOFC) fed by green H2 has emerged as a viable option to simultaneously supply high-grade heat and renewable electricity to DAC.

The longer supply chain for L-DAC integrated with green H2 fed SOFC introduces indirect environmental impacts from installation of renewable energy sites, and presents additional risks and environmental considerations for H2 storage and transportation. These unintended consequences could hinder the DAC from scaling and effectively operating. This research therefore aims to use life cycle assessment (LCA) to thoroughly evaluate the life cycle impacts of an L-DAC system integrated with green H2-fed SOFC, which will highlight key environmental considerations for the large-scale deployment of the proposed system. Beyond the standalone DAC system, environmental footprint associated with SOFC system, H2 production, storage, and transportation processes, as well as renewable energy systems are considered.

Given the current scarcity of LCA studies for DAC systems [2], this research is essential by providing a comprehensive analysis for the feasibility and reliability of demonstrating large-scale L-DAC integrated H2-fed SOFC system.

[1] Net Zero Strategy: Build Back Greener; [2] Breyer, et al. Joule, Volume 3, Issue 9, Pages 2053-2057.

What is this research investigating?

This proposed research focuses on the use of LCA to evaluate environmental impacts of an integrated L-DAC-H2-fed SOFC system. The size and land use for renewable energy installations to achieve enough H2 output for SOFC and L-DAC operation will be discussed. Compatible H2 electrolyser process and storage facility will also be considered to address the intermittency of renewable energy under different availability conditions. The LCA will be carried out in accordance with ISO Standards 14040 and 14044 and based on the function unit of capturing 1 Mt CO2 annually from the air.

The research tasks comprise:
1. The facility size and land use for renewable energy sites necessary to produce sufficient H2 will be assessed. Impacts on the varying availabilities to supply renewable energy will be evaluated on the H2 production and storage.
2. Collating input and output energy and material data for all components involved in the integrated system from the construction, operation, and dismantling stages.
3. Developing LCA model by using commercial LCA software, such as SimaPro, etc.
4. Mapping and interpretating environmental impacts categories to different stages and components.
5. Highlighting key environmental considerations regarding future scale-up of L-DAC with H2-fed SOFC.

What does the research hope to achieve?

By contributing insights into multifaceted environmental impacts, the outcomes from this research will greatly inform the stakeholders from policymakers to industrial partners who have intents to implement large-scale DAC with renewable energy to make strategic decisions on environmentally sustainable DAC operation.

The project’s findings will be published through the scientific journals to broaden the research base, and presented at relevant conferences to foster interdisciplinary discussion and further collaboration.

This research will also support the educational objectives of Durham University by integrating research methodology and findings into the undergraduate learning and development program.