EfW-UPCC: Techno-Economic Assessment of Ultra-high Post-Combustion Capture in Energy from Waste Plants (Flexible Funding 2024)

Dr Stavros Michailos, University of Hull, was awarded funding in the UKCCSRC’s Flexible Funding 2024 call to look at “EfW-UPCC: Techno-Economic Assessment of Ultra-high Post-Combustion Capture in Energy from Waste Plants”.

Introduction

Decarbonising industrial clusters is essential to the UK’s net-zero target by 2050. This commitment has designated Carbon Capture Utilisation and Storage (CCUS) as a necessity and not an option. Post-Combustion Capture (PCC) of CO₂ using amines is expected to dominate, with two out of the three UK government-funded Track-1 CCS Cluster Sequencing capture projects to be amine-based PCC plants¹. PCC offers the advantage of retrofitting existing infrastructure, making it a practical and cost-effective option for multiple industries such as energy from waste, and is also being considered for new-builds².

Background

EfW plants have the potential to replace landfills while generating low carbon electricity and heat. When PCC is added, then the EfW+PCC assembly can be a carbon dioxide removal (CDR) technology and achieve negative emissions since typically up to 50% of the CO₂ contained in the flue gas is biogenic. Obviously, the higher the capture fraction, the higher the chances for carbon removal to account also for upstream emissions.

Up until recently, the conventional wisdom has been – largely because it was a ‘standard’ baseline used in studies comparing costs – that capturing 90% of the CO₂ in a flue gas stream was both good enough and the best that could be done to minimise the cost per tonne of CO₂ captured. But, to help deliver net-zero fossil CO₂ stack operation ( or 100% of the added fuel CO₂ or 100% fossil CO₂ capture), combustion applications fitted with PCC should ideally operate at such a manner that the whole amount of the fossil CO₂ added to the air is captured and hence the vented gas should contain the same amount of CO₂ as the combustion air; this entails gross capture fraction from the EfW flue gas of ~99.7%.

Aim

The main aim of the project is to establish feasible design and operational windows of ultra-high capture fractions up to up to 100% of the fossil-based CO₂ emissions and reveal the true cost of achieving 100% capture and challenge the assumption that such high capture levels are prohibitively expensive.

Novelty

A key innovation in this study is the use of low lean solvent loadings (<0.15 molCO₂/molMEA) and moderately elevated desorber pressures (2.4 bara). This increases the CO₂ mass transfer rate without demanding massive changes to absorber height (main CAPEX) or solvent flow rates and for specific reboiler duties (SRD) that lie well within the range of reported energy penalty for 90–95% capture, i.e. between 3 and 4 GJ/tCO₂^3,4. In essence, it lets existing infrastructure do more with only minor upgrades.

Results

Mass and energy balances have been established (through Aspen Plus modelling) for different absorber heights, i.e. 20 (2 beds x10), 24 (3 beds x8) and 30m (3 bedsx10), and capture fractions of 95% and 100%. All cases, include intercooling at 40°C (in-out). The optimum lean loading for EfW flue gas has been identified at 0.12 molCO₂/molMEA. Figure 1 is the SRD for different capture fraction and absorber heights. Taller absorbers allow for lower L/G ratios and higher rich loading which have appositive impact on the SRD. The increase of SRD from 95% to 100% is 13.5%, 6.7% and 3.6% for 20, 24 and 30m absorber heights.

Figure 1. The SRD for different absorber packing heights and capture fractions

The 24 m absorber is likely to be the industrial standard for PCC. The CAPEX breakdown for this case is presented in Figure 2A. Regeneration costs include stripping and solvent reclaiming with the latter to account for approximately 8% of the regeneration costs. On the other hand, electricity costs—primarily reflecting steam consumption and assuming a coefficient of performance (COP) of approximately 4—represent a significant portion of the operating expenses, i.e., 62%.

Subsequently, the cost of CO₂ capture has been calculated. The increase in the capture cost from 95% to 100& capture is 5.72%, 3.66% and 3.25% for the 20, 24 and 30m absorber, respectively. This is a significant improvement against the consensus that ultra-high capture fractions are related to excessive costs. Further, the marginal cost of capture of transitioning from 95% to 100% fossil CO₂ capture is 175, 141 and 102 £/tCO₂ for the 20, 24 and 30m absorber, respectively; in all cases, these figures are lower than current and projected direct air capture costs.

Figure 2. CAPEX (A) and OPEX (B) breakdown for the 24m absorber and capture fractions of 95% and 100%

Figure 3. The cost of CO2 captured for different absorber packing heights and capture fractions

Conclusions

The path to net-zero will require scalable technologies that can deliver deep decarbonisation at reasonable costs. By showing that 100% fossil CO₂ capture from EfW plants is not only technically achievable but also cost-competitive, this work lays the groundwork for new CCUS strategies, informs UK government policy and boosts investor confidence.

Outputs

• Michailos, M. Lucquiaud, A. D. Benz, D. Mullen, W. Elliott and J. Gibbins. A Performance Modeling Study for Zero Fossil CO2 Stack Operation and Solvent Thermal Reclaiming in Post-Combustion Capture Industrial Applications Industrial & Engineering Chemistry Research 2025 Vol. 64 Issue 13 Pages 7100-7114 https://doi.org/10.1021/acs.iecr.4c04530
• Qurrotin Ayunina, S. Michailos, MF Rojas Michaga, K. Rabea, K. J Hughes, L. Ma, D. Ingham, M. Pourkashanian. Conceptual design and thermodynamic investigation of novel energy and fuel generation systems from municipal waste coupled with carbon capture and storage, Energy Nexus, Volume 18, 2025, 100460, https://doi.org/10.1016/j.nexus.2025.100460

Acknowledgments

SM would like to acknowledge the Engineering and Physical Sciences Research Council (EPSRC) under the United Kingdom CCS Research Centre grant EP/W002841/1 (Flexible Funding 2024).

Read more on Stavros’s Flexible Funding 2024 project page.