Weekly CDR Publication Highlights (5 December 2024)
This week’s selected publications cover a wide range of issues related to soil carbon sequestration, weathering, optimization of CDR portfolios, biomass gasification and direct air capture.
Managing Soil Carbon Sequestration: Assessing the Effects of Intermediate Crops, Crop Residue Removal and Digestate Application on Swedish Arable Land
Abstract
Promoting the bioeconomy to aid in the achievement of sustainability goals has increased demand for biomass as feedstock. Residual biomass from agricultural production is an attractive option, as it is a by-product that does not compete with food production. However, crop residues are important for the preservation of soil quality, especially for the maintenance of soil organic carbon. Therefore, their use can conflict with environmental goals and initiatives that aim to preserve soil fertility and carbon stocks. Nevertheless, the adoption of intermediate crops could compensate for the negative effects of crop residue removal. Moreover, if crop residues are used for a bioeconomy pathway such as biogas production, the resulting digestate derived from the anaerobic digestion process could be returned to the soil, providing an input of highly recalcitrant carbon. In this study, we modeled the effects of removal of crop residues, the cultivation of intermediate crops, and the application of digestate on Swedish soil organic carbon stocks. Our results suggest that the inclusion of intermediate crops could raise the carbon stocks at equilibrium by an average of 1.93 t C ha−1 (~3% increase) with a notable spatial variation. Digestate application showed a higher average increase (3.3 t C ha−1, ~5%) with an even higher variation. The removal of crop residues was detrimental in some areas, resulting in a loss of carbon, which could not be compensated for entirely by the introduction of intermediate crops or digestate recycling. Combining these two practices showed overall positive effects on soil organic carbon stocks; however, the results cannot be generalized at any spatial location, and we emphasize the importance of assessments tailored to local conditions.
Latorre, S., Bjornsson, L., Prade, T. (2024) Managing Soil Carbon Sequestration: Assessing the Effects of Intermediate Crops, Crop Residue Removal and Digestate Application on Swedish Arable Land Global Change Biology Bioenergy 16 (12) 1-15.
Read the full paper here: Managing Soil Carbon Sequestration: Assessing the Effects of Intermediate Crops, Crop Residue Removal and Digestate Application on Swedish Arable Land I Global Change Biology Bioenergy
Prospects for the Potential Carbon Sink Effects of Afforestation to Enhance Weathering in China
Abstract
The carbon sink effect of afforestation is key to mitigating current global warming. China’s planted forest area accounts for more than a quarter of the global afforestation efforts and has made a prominent contribution to carbon sequestration. Previously, afforestation as a carbon sink was primarily evaluated in terms of the biomass carbon pool and soil organic carbon pool. Plants play a significant role in enhancing the chemical weathering of rocks and minerals, which can lead to more CO2 consumption. However, role of plants in enhancing chemical weathering and contributing to CO2 removal has not been considered when calculating the artificial sink. This paper reviews relevant studies on the carbon sinks from weathering and forest biomass in China and synthesizes the research on how plants affecting weathering in natural ecosystems. Based on this, we estimate the atmospheric CO2 consumption from afforestation-enhanced weathering in China. If afforestation increases the natural weathering rate by a factor of four on average, the national carbon sink through weathering could increase by 33 %. This increase in carbon sink capacity amounts to 35 million tonnes CO2/y and represents ∼1/6 of China’s afforestation biomass carbon sink during 2014–2018. The significant contribution underscores the need for further comprehensive research into the carbon sink effect of afforestation-enhanced weathering in the future. Understanding how afforestation, global warming, and other anthropogenic activities interact to affect weathering will provide insights to accurately evaluate the role of large-scale afforestation in China’s efforts to meet its “dual-carbon” goals and mitigate global warming.
Wu, W., Nel, W., Ji, J., Chen, J. (2024) Prospects for the Potential Carbon Sink Effects of Afforestation to Enhance Weathering in China. Journal of Asian Earth Sciences 276 (106370).
Read the full paper here: Prospects for the Potential Carbon Sink Effects of Afforestation to Enhance Weathering in China I Journal of Asian Earth Sciences
Optimizing Carbon Dioxide Removal Portfolios Considering the Cost of Permanent Removal
Abstract
Negative emission technologies (NETs) are now considered essential for achieving net-zero emissions by mid-century. These technologies work by removing carbon dioxide from the atmosphere and storing it in various mediums, such as biomass, soil, deep underground, or the ocean. Rather than relying on a single large-scale NET, portfolios offer a way to manage the risks and sustainability issues associated with these technologies. Optimizing the deployment of NET portfolios is an emerging area of research. One challenge in this optimization is considering the permanence of carbon dioxide removal (CDR) for different technologies, as some NETs are more susceptible to reversal (e.g., forests are at risk of fires) than others (e.g., geological storage has a lower risk of reversal). CDR permanence is crucial in NET portfolio optimization because it affects the actual CDR potential of the portfolio over time. Currently, there is a lack of studies considering the permanence of NETs in portfolios. One approach to address this is by using time-evaluated costs, where the various NETs have different costs of permanent removal (CPR) depending on the considered planning horizon or time of permanence. This work aims to bridge the research gap by applying the concept of CPR in optimizing NET portfolios. Two mixed-integer linear programming models are used to optimize a NET portfolio under CPR, resource, budget, and capacity constraints, subject to target CDR. Different times of permanence (from 25 to 1,000 y) are investigated. The results show varying NET portfolios depending on the time of permanence considered. This work contributes to the analysis of decarbonization portfolios for decision-making to mitigate climate change.
Migo-Sumagang, M., Tan, R. R., Aviso, K.B. (2024) Optimizing Carbon Dioxide Removal Portfolios Considering the Cost of Permanent Removal. Chemical Engineering Transactions 113 427-432.
Read the full paper here: Optimizing Carbon Dioxide Removal Portfolios Considering the Cost of Permanent Removal I Chemical Engineering Transactions
Robust Simulation Platform of Biomass Gasification Process with Carbon Capture for Energy Vector Polygeneration
Abstract
Recent studies underscore the need for advanced technologies to limit global warming to below 2 °C and prevent irreversible climate change. This urgency is reflected in initiatives by the United Nations Framework Convention on Climate Change (UNFCCC) and the International Energy Agency (IEA). Carbon-negative solutions like the biomass gasification-carbon capture and storage (BECCS) hybrid systems are crucial, as BECCS is currently the only large-scale technology capable of removing CO2 from the atmosphere. BECCS integrates sustainable biomass conversion via gasification combined heat and power (CHP) to generate electricity and heat, with post-combustion carbon capture (PCC) being one of the most mature CCS technologies available. In this work, a robust simulation platform of biomass gasification with PCC technology is developed using Aspen Plus software. The BECCS system is operated using palm kernel shells as a feedstock, while monoethanolamine with a concentration of 30 wt.% is used for the PCC plant. The performance evaluation of the BECCS system is conducted via sensitivity analysis. The simulation analysis shows that an increase in gasification temperature produces higher quality syngas with the optimal gasification temperature being 850 (C. Meanwhile, the optimal reboiler temperature obtained is 120.6 (C, indicating the optimal temperature for CO2 desorption in the stripper. This study achieved a carbon removal rate of 99.94 %, and the highest power generated was observed to be 18 kW. The output from this robust simulation platform enables the minimization of overall emissions to below zero, offsetting emissions in other sectors where reductions are more challenging to achieve.
Macdonald J.H., Mohd Paad K., Kamaruzaman N., Yamanaka S., Abbas A., Abdul Manaf N. (2024) Robust Simulation Platform of Biomass Gasification Process with Carbon Capture for Energy Vector Polygeneration. Chemical Engineering Transactions 113 535-540.
Read the full paper here: Robust Simulation Platform of Biomass Gasification Process with Carbon Capture for Energy Vector Polygeneration I Chemical Engineering Transactions
Electrochemical C02 Fixation and Release Cycle Featuring a Trinuclear Zinc Complex for Direct Air Capture
Abstract
CO2 capture technology can mitigate greenhouse gas emissions and global warming. CO2 capture driven by electrochemical reactions is attractive because the operation is carried out at normal temperature and pressure and involves a simple input system using electrical energy. Although promising metal complexes with high CO2 fixation performance have been reported, there are few studies on systems that combine electrochemical reactions and metal complexes. Here, we demonstrated stable CO2 fixation-release cycles using an electrochemical system with trinuclear Zn(II) complex (Zn3L) as the CO2 fixative and an ionic liquid as a supporting electrolyte for the stable operation. This system showed a faster CO2 fixation rate than that of an aqueous alkaline solution at the same concentration. Continuous release and refixation of CO2 were achieved by decomposition and reconstruction of the complex structure induced by H+ and OH- supplied from a bipolar membrane equipped in the electrolytic cell. The CO2 fixation-release cycle was demonstrated even for dilute CO2 (450 ppm) in air, where the CO2 capture rate reached approximately 46% of CO2 contained in the air under an air flow condition of 200 mL⸱min-1. This case, combining electrochemical drive and metal complexes, will provide a new option for CO2 capture technology.
Murase M, Sakamoto N, Uyama T, Nonaka T, Ohashi M, Sato S, Arai T, Itoh T. (2024) Electrochemical CO2 Fixation and Release Cycle Featuring a Trinuclear Zinc Complex for Direct Air Capture. Angewandte Chemie International Edition
Read the full paper here: Electrochemical C02 Fixation and Release Cycle Featuring a Trinuclear Zinc Complex for Direct Air Capture I Angewandte Chemie International Edition