CO₂-removal News

Peer-reviewed Publications

Linke et al. (2024): The geochemical evolution of basalt Enhanced Rock Weathering systems quantified from a natural analogue

T. Linke, E.H. Oelkers, K. Dideriksen, S.C. Möckel, S. Nilabh, F. Grandia, S.R. Gislason IN: Geochimica et Cosmochimica Acta, 370, https://doi.org/10.1016/j.gca.2024.02.005

Substantial quantities of fine-grained basaltic dust have fallen on South Iceland soils over at least the past 3300 years, making this region an ideal natural analogue to define the long-term consequences of current Enhanced Rock Weathering efforts. A relatively pristine South Iceland Gleyic/Histic Andosol, 3 m in height, receiving approximately 1250 mm of rainfall annually was selected for this study. This soil receives an estimated 500–800 g/m2 y of basaltic dust. The soil waters in this system were regularly sampled as a function of depth from May to November 2018. The fluid pH, alkalinity and the concentrations of most major elements increased with depth as the fluids became more reduced. In contrast, whereas numerous toxic trace metals are initially released to the fluid by the dissolution of the basalt near the surface they are scavenged at depth likely due to their uptake by secondary minerals.

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Peer-reviewed Publications

Markkanen et al. (2024): Sustainable negative emissions in Europe: Evaluating scenarios to meet carbon neutrality by 2050

Johanna Markkanen, Kati Koponen, Antti Lehtilä IN: Environmental Research Letters, 2024, https://doi.org/10.1088/1748-9326/ad71e1

With the Pan-European TIMES-VTT model, the authors studied pathways for carbon neutrality by 2050 for 31 European countries by modelling a large portfolio of varius terrestial and technological carbon dioxide removal (CDR) strategies. Negative emission technologies and practices (NETPs) such as af-/reforestation, soil carbon sequestration, bioenergy with carbon capture and storage, direct air capture and storage, biochar, and enhanced weathering, were considered. Three different storylines were created to describe the role for NETPs in varying future developments. The scenario storylines illustrated potential opportunities and constraints for a large scale NETP implementation focusing on 1) optimistic technology development, 2) strict protection of planetary boundaries, and 3) increased self-sufficiency due to geopolitical risks with policy fragmentation.

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Peer-reviewed Publications

Chiaramonti et al. (2024): Biochar is a long-lived form of carbon removal, making evidence-based CDR projects possible

David Chiaramonti, Johannes Lehmann, Franco Berruti, Paola Giudicianni, Hamed Sanei, Ondrej Masek IN: Biochar, 6,
https://doi.org/10.1007/s42773-024-00366-7

In this work, the authors discuss the durability of the carbon in biochar and the need for analytical techniques to support stakeholders on a project level. The different ecologically relevant groups of carbon forms contained in biochar are presented, and possible project-based methods to assess the quality and durability of the product versus the regulatory requirements for the permanence of carbon removals are summarized.

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Peer-reviewed Publications

Cao et al. (2024): Highly efficient direct air capture using solid–liquid phase separation in aqueous diamine solution as sorbent

Furong Cao, Soichi Kikkawa, Hidetaka Yamada, Seiji Yamazo IN: Bulletin of the Chemical Society of Japan, 97, 9, https://doi.org/10.1093/bulcsj/uoae096

In this work, a series of aqueous diamine solutions was examined for 400 ppm CO2 absorption at ambient temperature. The absorbents exhibited CO2 absorption with molar ratio of 1 molCO2/molamine, and aqueous isophorone diamine (IPDA) in particular showed >99% CO2 removal even under a 500 mL min−1 flow of 400 ppm CO2–N2 with the contact rate of 13,761.5 h−1 between CO2 and IPDA aqueous solution and the CO2 absorption rate of 4.46 mmol/L min. A precipitate of carbamic acid of IPDA was formed by reaction with CO2, and the CO2 removal efficiency was enhanced by increasing the solution viscosity by the formation of this precipitate.

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Peer-reviewed Publications

Nature – Yao et al. (2024): Carbon sequestration potential of tree planting in China

Ling Yao, Tang Liu,Jun Qin, Hou Jiang, Lin Yang, Pete Smith, Xi Chen, Chenghu Zhou, Shilong Piao IN: Nature Communications, 15, https://doi.org/10.1038/s41467-024-52785-6

China’s large-scale tree planting programs are critical for achieving its carbon neutrality by 2060, but determining where and how to plant trees for maximum carbon sequestration has not been rigorously assessed. Here, the authors developed a comprehensive machine learning framework that integrates diverse environmental variables to quantify tree growth suitability and its relationship with tree numbers. Then, their correlations with biomass carbon stocks were robustly established. Carbon sink potentials were mapped in distinct tree-planting scenarios.

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Peer-reviewed Publications

Science – Zeng et al. (2024): 3775-year-old wood burial supports “wood vaulting” as a durable carbon removal method

Ning Zeng, Xinpeng Zhao, Ghislain Poisson, Bryson Clifford, Yu Liu, He Liu, Taotao Meng, Laura Picard, Elisa Zeng-Mariotti, Ben Zaitchik, Liangbing Hu IN: Science, DOI: 10.1126/science.adm8133

The authors found a 3775-year-old ancient wood log buried 2 meters belowground that was preserved far beyond its expected lifetime. The wood had near-perfect preservation, with carbon loss less than 5% compared to a modern sample. The lack of decay is likely due to the low permeability of the compact clay soil at the burial site. The observation suggests a hybrid nature-engineering approach for carbon removal by burying woody biomass in similar anoxic environments.

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Peer-reviewed Publications

Li et al. (2024): Competing Kinetic Consequences of CO2 on the Oxidative Degradation of Branched Poly(ethylenimine)

Sichi Li, Yoseph Guta, Marcos F. Calegari Andrade, Elwin Hunter-Sellars, Amitesh Maiti, Anthony J. Varni, Paco Tang, Carsten Sievers, Simon H. Pang, Christopher W. Jones IN: Journal of the American Chemical Society, 2024, https://doi.org/10.1021/jacs.4c08126

Amine-functionalized porous solid materials are effective sorbents for direct air capture (DAC) of CO2. However, they are prone to oxidative degradation in service, increasing the materials cost for widespread implementation. While the identification of oxidation products has given insights into degradation pathways, the roles of some species, like CO2 itself, remain unresolved, with conflicting information in the literature. Here, the authors investigate the impact of CO2 on the oxidative degradation of poly(ethylenimine)–alumina (PEI/Al2O3) sorbents under conditions encompassing a wide range of CO2-air mixture compositions and temperatures relevant to DAC conditions, thereby reconciling the conflicting data in the literature.

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Peer-reviewed Publications

Breunig et al. (2024): Life cycle impact and cost analysis of quarry materials for land-based enhanced weathering in Northern California

Hanna M. Breunig, Patricia Fox, Jeremy Domen, Ram Kumar, Ricardo Jorge Eloy Alves, Kateryna Zhalnina, Anne Voigtländer, Hang Deng, Bhavna Arora, Peter Nico IN: Journla of Cleaner Production, 2024, https://doi.org/10.1016/j.jclepro.2024.143757

Enhanced weathering (EW) has been demonstrated in laboratory and field tests, but great uncertainty remains regarding the life-cycle of using locally available rocks on candidate soils. The authors evaluate the life-cycle impacts, job creation, and cost of scenarios where fines and rocks mined from quarries in Oregon and Northern California are transported by truck and tilled into agricultural soils.

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Science-Policy Documents

Burke & Schenuit (2024): Conditional fungibility: sequencing permanent removals into emissions trading systems

Josh Burke, Felix Schenuit IN: Environmental Research Letters, DOI 10.1088/1748-9326/ad796b

First, the authors present the policy context and a mapping and conceptual distinction of five groups of measures applicable to address varying levels of permanence in CDR policy. Second, they make the case for limiting the fungibility of different CDR methods with each other and with fossil CO2 emissions. Third, and building on the identified measures and conditional fungibility, the authors present a sequencing strategy for integrating permanent removals into existing compliance carbon markets.

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Peer-reviewed Publications

Nature – Moustakis et al. (2024): Temperature overshoot responses to ambitious forestation in an Earth System Model

Yiannis Moustakis, Tobias Nützel, Hao-Wei Wey, Wenkai Bao, Julia Pongratz IN: Nature Communications, https://doi.org/10.1038/s41467-024-52508-x

Here, the authors develop an ambitious Afforestation/Reforestation scenario by harnessing 1259 Integrated Assessment Model scenarios, restoration potential maps, and biodiversity constraints, reaching 595 Mha by 2060 and 935 Mha by 2100. They then force the Max Planck Institute’s Earth System Model with this scenario which yields a reduction of peak temperature by 0.08°C, end-of-century temperature by 0.2°C, and overshoot duration by 13 years. Afforestation/ Reforestation in the range of country pledges globally could thus constitute a useful mitigation tool in overshoot scenarios in addition to fossil fuel emission reductions, but socio-ecological implications need to be scrutinized to avoid severe side effects.

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