Why is this research needed?

The UK government is aiming towards a 78% greenhouse gas emissions reduction by 2035 in order to keep the global temperature rise below the Paris Accord targets. Most mitigation scenarios that achieve these ambitious goals rely on BioEnergy with Carbon Capture and Storage (BECCS), which plays a pivotal role in more than 85% of the pathways proposed by the International Panel on Climate Change. With the UK anticipating an increase in biomass combustion, the question of biomass waste minimisation and management is ever more pressing, as evidenced by a recent UK government policy statement. Further, these biomass combustion products (BCPs) present a significant environmental (issues with secondary pollution) and economic burden, hindering widespread industrial deployment of BECCS.

A considerable amount of combustion ash is currently being landfilled in the UK (~30% of total combustion ash produced). It is expected that by 2050, over 10% of UK energy will be generated via biomass and, thus, a growing generation of BCP is expected in the forthcoming years. Landfilling combustion ash is costly and can potentially threaten the ecological environment. With an increasing interest in biomass combustion in the UK (as commercially demonstrated by Drax power plant) and, with inherently different chemical and physical ash properties compared to that of coal, management and utilisation of BCA can present a considerable challenge, yet still a potential opportunity in the power generation sector in the future.

Nevertheless, due to specific properties of BCPs, applications in adsorption-based CO2 capture are a proposed avenue for simultaneous solution to both environmental and economic issues. Our lab-scale proof-of-concept studies have demonstrated potential for producing cost-effective BCP-derived adsorbents directly from Drax combustion residues (carbonaceous sorbents capturing 0.69 mmolCO2/g and 1.65 mmolCO2/g for zeolite-based materials). Industrial deployment, in contrast, has yet to be achieved due to a lack of investigations into key adsorption operational variables such as particle size (which has an immense impact on the kinetics and pressure drop). This proposal aims to address these challenges (both operational and environmental) to facilitate an upwards transition in technology readiness level.

This proposal builds upon our previously-successful 2021 UKCCSRC Flexible Funding (EP/P026214/1) – which has successfully demonstrated the proof of concept – and aims to investigate, identify and improve the operational and environmental challenges of BCP-derived adsorbent, using industrial-grade Drax BCP as a potential precursor for the synthesis of effective yet low-cost adsorbents used in post-combustion carbon capture.

What is this research investigating?

This research aims to carefully investigate both the environmental and operational challenges associated with our existing waste-derived adsorbents, synthesised from Drax biomass combustion ash via (EP/P026214/1), and to improve the techno-economics of the process by employing a robust yet cost-effective activation technique. In this context, the research objectives comprise:

1. To employ an efficient yet novel approach to activating/synthesising our existing waste-derived adsorbents, hence a significant reduction in material synthesis costs (Work Package 1).
2. To investigate the impact of particle size of our adsorbents on the adsorption uptake capacity, kinetics, mass transfer and pressure drop, using our existing fixed-bed reactor (Work Package 2).
3. To study the leaching behaviour of our waste-derived adsorbent particles (Work Package 3).

What does the research hope to achieve?

This research bridges the gap between academic research and the industrial application, by investigating the environmental and operational challenges associated with our cost-effective yet efficient waste-derived adsorbents. The findings in this work will be able generate new knowledge within these two core areas.

1) The findings in WP1 will be useful to both chemists and chemical engineers along with material scientists, as this will reveal the suitability of ultra-sonication techniques on activation of our prepared adsorbents.

2) The findings in WP2 will be useful to chemical engineering scientists working on adsorption processes, looking to improve process efficiency and advanced optimisation based on experimentally-generated datasets. Here the data produced (e.g. impact of particle size on adsorption behaviour and pressure drop in a fixed-bed column) would enable an in-depth experimentally-informed process modelling.

3) In WP3, given the nature of our adsorbents (i.e. waste-derived), we will carefully study the leaching behaviour of our optimised adsorbents. This dataset would be crucial in large-scale application of our adsorbents and their disposal methods. As a result, the WP3 dataset would be immediately applicable to industrial/large-scale settings, and plant operators.