CO₂-removal News

Nature – Pan et al. (2024): The enduring world forest carbon sink

Yude Pan, Richard A. Birdsey, Oliver L. Phillips, Richard A. Houghton, Jingyun Fang, Pekka E. Kauppi, Heather Keith, Werner A. Kurz, Akihiko Ito, Simon L. Lewis, Gert-Jan Nabuurs, Anatoly Shvidenko, Shoji Hashimoto, Bas Lerink, Dmitry Schepaschenko, Andrea Castanho, Daniel Murdiyarso IN: Nature, https://doi.org/10.1038/s41586-024-07602-x

To provide a ground-based long-term assessment of the contribution of forests to terrestrial CO2 uptake, the authors synthesized in situ forest data from boreal, temperate and tropical biomes spanning three decades. They found that the carbon sink in global forests was steady, at 3.6 ± 0.4 Pg C yr−1 in the 1990s and 2000s, and 3.5 ± 0.4 Pg C yr−1 in the 2010s. Despite this global stability, our analysis revealed some major biome-level changes. Carbon sinks have increased in temperate (+30 ± 5%) and tropical regrowth (+29 ± 8%) forests owing to increases in forest area, but they decreased in boreal (−36 ± 6%) and tropical intact (−31 ± 7%) forests, as a result of intensified disturbances and losses in intact forest area, respectively.

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Caldecott & Johnstone (2024): The Carbon Removal Budget: theory and practice

Ben Caldecott, Injy Johnstone IN: Carbon Management, 15, https://doi.org/10.1080/17583004.2024.2374515

There are ongoing questions as to how we can increase the supply of quality CDR whilst at the same time ensure equitable distribution of that same CDR, both within and between countries and non-state actors. To explore these phenomena, the authors introduce and define the concept of a Carbon Removal Budget (CRB), illustrate how it can apply to different contexts and scales, and distinguish it from the related but distinct concept of the carbon budget. They further estimate the global CRB, review its constraints and quality considerations and outline potential utilisation pathways and principles. They then examine the potential application of the CRB as a tool on which both public and private decision-makers can use to assess the feasibility of their nationally determined contributions and/or net-zero transition plans.

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De Marco et al. (2024): Energy demand and savings opportunities in the supply of limestone and olivine-rich rocks for geochemical carbon dioxide removal

Serena De Marco, Stefano Caserini, Thorben Amann, Mario Grosso IN: Environ. Res. Lett., 19, https://doi.org/10.1088/1748-9326/ad4efb

The large-scale implementation of geochemical Carbon Dioxide Removal (CDR) approaches such as Enhanced Weathering (EW) and Ocean Liming (OL) will require the extraction and processing of large amounts of limestone and olivine-rich rocks. Based on a literature review, surface mining, comminution, their related sub-stages, and long-haul transportation have carefully been surveyed to elucidate the order of magnitude of the energy demand, the technical challenges posed by each operation, and the potential energy-savings achievable by applying opportune strategies.

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Nature – Metcalfe et al. (2024): Separation and concentration of CO2 from air using a humidity-driven molten-carbonate membrane

Ian S. Metcalfe, Greg A. Mutch, Evangelos I. Papaioannou, Sotiria Tsochataridou, Dragos Neagu, Dan J. L. Brett, Francesco Iacoviello, Thomas S. Miller, Paul R. Shearing, Patricia A. Hunt IN: Nat energy, 2024, https://doi.org/10.1038/s41560-024-01588-6

Here the Authors report a molten-carbonate membrane that can ‘pump’ CO2 from a 400 ppm input stream (representative of air) to an output stream with a higher concentration of CO2, by exploiting ambient energy in the form of a humidity difference. The substantial H2O concentration difference across the membrane drives CO2 permeation ‘uphill’ against its own concentration difference, analogous to active transport in biological membranes.

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Victor & Nichols (2024): Impact of carbon dioxide removal technologies on deep decarbonization: EMF37 MARKAL–NETL modeling results

Nadejda Victor, Christopher Nichols IN: Energy and Climate Change 5, 100143, https://doi.org/10.1016/j.egycc.2024.100143

This paper examines the MARKAL-NETL modeling results for the Energy Modeling Forum study on Deep Decarbonization and High Electrification Scenarios for North America (EMF 37) with a specific focus on carbon dioxide removal technologies and opportunities under different scenario guidelines, policies, and technological advancements.

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Fischer et al. (2024): Distinguishing mature and immature trees allows estimating forest carbon uptake from stand structure

Samuel M. Fischer, Xugao Wang, Andreas Huth IN: Biogeosciences, 21, https://doi.org/10.5194/bg-21-3305-2024

Biomass production (net primary production – NPP) and net ecosystem exchange (NEE) are subject to respiration and other carbon losses, which vary with local conditions and life history traits. Here, the authors use a simulation approach to study how these losses impact forest productivity and reveal themselves in forest structure. The authors fit the process-based forest model FORMIND to a 25 ha inventory of an old-growth temperate forest in China and classify trees as “mature” (fully grown) or “immature” based on their intrinsic carbon use efficiency.

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Kaur et al. (2024): Quantifying the carbon sequestration potential of different soil management practices aimed at increasing organic content in soil and reducing the usage of chemical inputs

Mandeep Kaur, N Nagabhooshanam, Prashant Sharma, Satyendra Singh, RVV Krishna IN: Global NEST Journal, 26, https://doi.org/10.30955/gnj.05932

This research focuses on quantifying the carbon sequestration potential of diverse soil management techniques aimed at increasing organic content in soil while minimizing the use of chemical inputs. It integrates a multidisciplinary approach, conducting field experiments across diverse agroecological regions with different soil types and cropping systems. Key practices under investigation include cover cropping, crop rotations, conservation tillage, compost application, organic amendments, integrated pest management (IPM), and precision agriculture. The study assesses their impact on soil organic carbon levels, greenhouse gas emissions, soil health indicators, and crop productivity through comprehensive data collection and analysis techniques. Statistical analyses and modeling are employed to quantify carbon sequestration rates, evaluate treatment effects, and assess environmental and agronomic benefits.

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Manning et al. (2024): Soil carbon management and enhanced rock weathering: The separate fates of organic and inorganic carbon

David A. C. Manning, Antonio Carlos de Azevedo, Caio F. Zani, Arlete S. Barneze IN: European Journal of Soil Science 75 (4), e13534, https://doi.org/10.1111/ejss.13534

Soil carbon management has been promoted as one of the few readily available strategies to mitigate the rising concentration of atmospheric CO2 and its associated impacts on climate change. One of these carbon management strategies is enhanced rock weathering which involves adding crushed silicate rocks to the soil. The approach requires careful interpretation of the differences between soil organic carbon (SOC) and soil inorganic carbon (SIC) and their measurement, with implications for land management and C credit accounting. In this Opinion, the authors emphasise the distinct nature and fates of SOC and SIC, advocating for their separate management, particularly in C credit schemes.

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Fam & Fam (2024): Review of the US 2050 long term strategy to reach net zero carbon emissions

Adam Fam, Sami Fam IN: Energy Reports 12, 845-860, https://doi.org/10.1016/j.egyr.2024.06.031

This review article condenses the multitude of technical and policy issues facing the US long-term strategythat lays out the pathway to reach the Paris Agreement goals, providing readers with an overview of the extent and magnitude of the challenges while outlining possible solutions.

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Ampah et al. (2024): Carbon dioxide removal and net zero emissions in Africa: an integrated assessment modelling based on three different land-based negative emission solutions

Jeffrey Dankwa Ampah, Sandylove Afrane, Humphrey Adun, Michael O Dioha, Ephraim Bonah Agyekum, Abdulfatah Abdu Yusuf, Mudassar Naseer, Olusola Bamisile IN: Environmental Research Letters 19 (8), 084021, https://doi.org/10.1088/1748-9326/ad5dcf

As the remaining carbon budget for limiting warming to 1.5 °C rapidly diminishes, it is clear that, besides decarbonization, the world will need to remove 100–1000 GtCO2 from the atmosphere by the end of the century. Yet, Africa, where many carbon removal schemes are planned, remains a ‚blindspot‘ in existing studies. There is limited understanding of the trade-offs and synergies associated with carbon removal within Africa’s energy-land-water system. To address this research gap, a stylized net-zero emissions in Africa by 2050 was modeled, with focus on three land-based biological carbon removal approaches: afforestation/reforestation, bioenergy with carbon capture and storage, and biochar.

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