This week’s publication highlights cover a wide range of topics related to bioenergy with carbon capture and storage, use of macroalgae products for CDR, recovery of arctic sea-ice, CDR policies and afforestation.
Exergy Analysis and Thermodynamic Optimization of a Bioenergy with Carbon Capture and Storage Gas Power Plant Using Monte Carlo Simulation of Sewage Sludge Composition
Abstract
An exergy analysis is performed on the negative CO2 emission gas power plant (nCO2PP), which integrates the fuel preparation, power generation and carbon capture process sections. The cycle is modeled in Aspen Plus coupled with REFPROP, combining deterministic and Monte Carlo stochastic approaches, the latter being a novelty in this work. In all cases studied, the simulations maintain the complex thermodynamic relationships. Exergy losses with areas of potential improvement are identified, while Monte Carlo simulation in Python generates sewage sludge composition, improving cycle realism. In the deterministic approach, the exergies are calculated for a single sewage sludge composition under ambient air conditions with relative humidity of 40 %, 50 % (base case) and 60 % and CO2 air concentration of 375 ppm, 417 ppm (base case) and 1000 ppm, representing a worst case scenario of CO2 increase until the year 2100. For the deterministic base case nCO2PP, the largest exergy losses are observed in the wet combustion chamber (127 kW, 62 % efficiency), gasification process (43 kW, 89 % efficiency), and water condensation in the gas scrubber (43 kW, 87 % efficiency), while the nCO2PP exergy efficiency, related to the chemical exergy of the sewage sludge, is 33.3 %. Sensitivity analysis on turbine vacuum and spray-ejector condenser suction pressure results in an increase of the nCO2PP efficiency by 0.3 % to 33.6 %. Monte Carlo results are incorporated into the Aspen Plus model after the base case optimization. These yield in a range of nCO2PP exergy efficiencies from 33.6 % to 39.7 % with a mean of 37.5 %.
Stasiak, K. et al. (2025) Exergy Analysis and Thermodynamic Optimization of a Bioenergy with Carbon Capture and Storage Gas Power Plant Using Monte Carlo Simulation of Sewage Sludge Composition 264 (125312) Applied Thermal Engineering.
Read the full paper here: Exergy analysis and thermodynamic optimization of a bioenergy with carbon capture and storage gas power plant using Monte Carlo simulation of sewage sludge composition - ScienceDirect
Carbon Dioxide Removal Dilemma of Macroalgae Products: Evidence from Carbon Footprint and Profitability
Abstract
Macroalgae can bio-sequester atmospheric CO2 into their biomass, thus it has been proposed and debated as a viable carbon dioxide removal strategy to mitigate climate change. We examine the carbon footprints of common macroalgae products through a “cradle-to-grave” life cycle assessment, and find carbon sequestration effect can only be accomplished by some specific macroalgae product types when they are properly stored rather than being used. We identify the product processing and usage stages in macroalgae’s life cycle contribute most carbon emissions, while the net primary production of macroalgae during growth only partially neutralizes its overall CO2 emissions. A sensitivity test for such life cycle model indicates employing clean energy and improving technical efficiency can potentially achieve net-zero for some macroalgae products e.g., biochar. However, even considering macroalgae’s ecological values, our profitability investigation concludes that macroalgae products for carbon sequestration are extremely unattractive to practitioners under current carbon pricing level.
Jiao, T. et al. (2025) Carbon Dioxide Removal Dilemma of Macroalgae Products: Evidence from Carbon Footprint and Profitability 492 (144870) Journal of Cleaner Production.
Read the full paper here: Carbon Dioxide Removal Dilemma of Macroalgae Products: Evidence from Carbon Footprint and Profitability I Journal of Cleaner Production.
Incomplete Arctic Sea-Ice Recovery under CO2 Removal and Its Effects on the Winter Atmospheric Circulation
Abstract
This study explores the response of Arctic sea ice to CO2 removal and its subsequent effects on the winter Northern Hemisphere atmospheric circulation. Using multimodel ensembles from the Carbon Dioxide Removal Model Intercomparison Project, we find that most models display incomplete Arctic sea-ice recovery when CO2 is stabilized back at preindustrial levels, with a deficit of sea-ice area of around 1 million km2. This sea-ice deficit is associated with residual equatorward-shifted wintertime midlatitude jets. Sea-ice perturbation experiments from the Polar Amplification MIP provide evidence of a causal influence of residual sea-ice loss on the atmospheric circulation. Model uncertainty in the magnitude of the residual North Atlantic jet shift can be largely explained by the relative magnitudes of residual Arctic and tropical warming across the models. These findings suggest that Arctic sea-ice loss is not fully reversible after CDR, which leads to residual changes in the mid-latitude atmospheric circulation.
Yu, H. et al. (2025) Incomplete Arctic Sea-Ice Recovery under CO2 Removal and Its Effects on the Winter Atmospheric Circulation 52 (5) Geophysical Research Letters.
Read the full paper here: Incomplete Arctic Sea-Ice Recovery under CO2 Removal and Its Effects on the Winter Atmospheric Circulation I Geophysical Research Letters.
Review of Economics and Policies of Carbon Dioxide Removal
Abstract
Purpose of review
Despite the increasing political attention and support, the high costs of many carbon dioxide removal (CDR) technologies remain a barrier to their large-scale deployment. We provide an overview of the economics for two key CDR options – BECCS and DACCS – and review proposed and existing CDR policies to address the “CDR gap” in achieving the long-term temperature goals of the Paris Agreement.
Summary
Although we lack detailed cost breakdowns of actual projects, our review suggests that the cost range for BECCS is generally lower than that for DACCS. The key cost parameter for BECCS is the sustainability of biomass feedstock, and for DACCS the energy intensity.
Recent Findings
Cost estimates for DACCS have increased due to experiences from commercial operation, for BECCS they are increasingly differentiated according to the sustainability of feedstock.
Oh. S. et al. (2025) Review of Economics and Policies of Carbon Dioxide Removal 12 (6) Current Sustainable/Renewable Energy Report
Read the full paper here: Review of Economics and Policies of Carbon Dioxide Removal I Current Sustainable/Renewable Energy Report
Resilient Tree-Planting Strategies for Carbon Dioxide Removal under Compounding Climate and Economic Uncertainties
Abstract
To meet decarbonization targets, nations around the globe have made ambitious commitments to expand forested land. Operationalizing these commitments requires choosing a planting strategy: How many trees should be planted, of which species, and where? Given those choices must be made now but have long-term consequences, such decisions are plagued by uncertainty. For example, species that are well suited to present conditions may perform poorly under future climates, yet those future climates are themselves highly uncertain. Using the exemplar of the United Kingdom, a nation committed to achieving net zero emissions by midcentury, we quantify key uncertainties pertaining to coevolving climate and economic conditions and examine how modern methods of decision-making under uncertainty can advise on planting choices. Our analysis reveals that the best planting strategy assuming a “high-emissions” future is radically different to that for a future that remains on a “near-historic” path. Planting for the former while experiencing the latter results in substantial net costs to UK society. Assimilating uncertainty into decision-making identifies planting strategies that diversify risk and significantly reduce the probability of high-cost outcomes. Importantly, our research reveals that the scope for mitigating risk through choice of planting strategy is relatively limited. Despite this persistent risk, we find that tree planting remains a highly cost-effective carbon removal solution when compared to alternative technologies, even when those alternatives are assumed to be riskless.
Cho, F. et al. (2025) Resilient Tree-Planting Strategies for Carbon Dioxide Removal under Compounding Climate and Economic Uncertainties Environmental Sciences. 122 (10) PNAS.
Read the full paper here: Resilient Tree-Planting Strategies for Carbon Dioxide Removal under Compounding Climate and Economic Uncertainties Environmental Sciences I PNAS.