Weekly CDR Publication Highlights
This week’s selected publications cover a wide range of issues such as carbon removal accounting, the use of membrane technology for carbon capture sequestration and direct air capture, the utilization of calcium-modified biochar in citrus orchids, the manner in which copper slag mineralizes in carbon as well as blue carbon.
Carbon Removal Accounting for a Sustainable Future: Distributing CO2 Flows in Multiservice Systems
Abstract
Carbon dioxide removal (CDR) systems are an integral part of sustainable pathways limiting global warming to less than 2.0 °C. When the sole purpose of CDR is capturing and storing atmospheric CO2, carbon registries offer detailed procedures to calculate the carbon removal credits. However, the registries do not address how to distribute CO2 flows when CDR provides additional services. Standardized, transparent rules for distributing CO2 flows among CDR services are required for the formation of efficient private and public carbon markets. The lack of such rules could result in double counting if those reductions are allocated to more than one service, decreasing the trustworthiness of carbon removal credits or deterring the delivery of an additional low-carbon service, thus limiting the economic viability and deployment of CDR. We examine allocation rules in carbon registries and carbon accounting guidelines, including their life cycle assessment (LCA) principles. We evaluate physical (mass-based) and non-physical (economic) allocation methods using a generic CDR system and find both to be unworkable. We then develop a mass balance (MB) approach which can reliably allocate captured and stored carbon (CSC) between carbon removal credits and other services based on the value CO2 removal in those markets. This practical approach to allocation can be used in a transparent way to provide flexibility that would allow CDR services to capture the value of the multiple services they provide and, through this, promote the deployment of these sustainable alternatives.
Rodriguez-Garcia, G., Brandao, M. & Anex, R. (2024) 16(4) Carbon Removal Accounting for a Sustainable Future: Distributing CO2 Flows in Multiservice Systems Sustainability 1-13.
Read the full paper here: Carbon Removal Accounting for a Sustainable Future: Distributing CO2 Flows in Multiservice Systems I Sustainability
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Membrane Technology for Carbon Capture Sequestration and Direct Air Capture - Current status and Perspective
Abstract
To limit warming to less than 2 °C by the end of this century, enormous R&D efforts towards carbon capture have been made. Membrane gas separation is a promising technology for carbon capture and sequestration (m-CCS) due to its higher energy efficiency and smaller carbon footprints than the traditional amine scrubbing methodology. However, CCS alone for carbon capture mainly from stationary industry emitters is insufficient to effectively lower the ambient CO2 concentration. Complementarily, carbon capture directly from ambient air (DAC) is largely required. The current DAC technology mainly focuses on liquid and solid sorbents which is energy-intensive for regeneration. Membrane gas separation for DAC (m-DAC) was rarely discussed due to the extremely diluted CO2 concentration (0.04 %) relative to flue gas (∼ 10–15 %) until the very recent process simulation revealed the technological possibility. Herein, we will present the current status of membrane technology for both CCS and DAC in terms of their pilot scale application and the potential applicable membrane materials including polymer-based membranes, inorganic membranes, and facilitated transport membranes. Technology possibility and energy consumption compared with bench-mark sorbents were specifically illustrated for m-DAC. Membrane performance with CO2 of more than 2,500 GPU and CO2/N2 selectivity of more than 680 was regarded as a rough goal for promising membrane materials applied to the m-DAC event based on a primitive energy consumption calculation. Challenges, conclusions, and prospects for m-CCS and m-DAC were made at the end of this review.
Hou, R., Yu, J., Xie, J., Hu, Y., Wang, L., Zhao, B. & Pan, Y. (2025) 360 (2) Separation and Purification Technology 1-15.
Read the full paper here: Membrane Technology for Carbon Capture Sequestration and Direct Air Capture - Current status and Perspective I Separation and Purification Technology
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Potential of Calcium-Modified Biochar for Soil Nutrient and Carbon Sequestration in Citrus Orchards
Abstract
To examine the mechanisms of organic carbon transformation and sequestration by biochar in citrus orchard soil, a 100-day organic carbon mineralization test was conducted using citrus orchard soil from a 5-year-old forest. Calcium-modified citrus peel biochar (OBC-Ca) was applied at rates of 0%, 1%, 2%, and 4%. The results indicated that different percentages of OBC-Ca significantly influenced the mineralization processes in citrus orchards. Specifically, the cumulative mineralization of soil organic carbon was notably reduced by 8.68% and 17.00% with the application of 2% and 4% OBC-Ca, respectively, compared to the control group. Random forest analysis revealed that microbial biomass carbon (MBC), readily oxidizable carbon (ROC), and dissolved organic carbon (DOC) were critical indicators for predicting the cumulative mineralization of soil organic carbon. MBC and ROC were found to inhibit the cumulative mineralization, while DOC promoted it. As the proportion of OBC-Ca applications increased, MBC rose by 2.63% to 10.46%, ROC increased by 16.41% to 108.59%, and DOC increased by 0.48% to 11.67%. Correlation analysis demonstrated a significant negative correlation between the cumulative mineralization rate of soil organic carbon and soil enzyme activity, with soil sucrase content increasing significantly by 216.42% to 393.44% compared to the control. The application of calcium-modified biochar effectively reduces carbon dioxide emissions from citrus orchard soils, with a 4% application yielding the most favorable outcomes for enhancing soil carbon sinks, thereby positively impacting the carbon sequestration potential of citrus orchard soil.
Bai, Y., Huang, R., Li, S., Li, X., Fan, Q., Liu, S. & Hu, L. (2024) 14 (12) Potential of Calcium-Modified Biochar for Soil Nutrient and Carbon Sequestration in Citrus Orchards. Agriculture 1-15.
Read the full paper here: Potential of Calcium-Modified Biochar for Soil Nutrient and Carbon Sequestration in Citrus Orchards I Agriculture
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The Carbon Mineralization Behavior of Copper Slag and Its Impact on Pozzolanic Reactivity
Abstract
The massive discharge of copper slag (CS) has led to serious environmental problems. Carbon mineralization, as a treatment method of solid waste, not only achieves carbon sequestration, but also enhances the pozzolanic activity. In this work, a novel exfoliation aqueous carbonation method combining aqueous carbon mineralization and wet grinding was proposed to evaluate the carbon mineralization behavior of CS at mild temperature and pressure. The results indicated that exfoliation aqueous carbonation exhibited higher mineralization degree than that of classical CO2 bubbling carbonation. The carbonation products of CS were mainly composed of amorphous carbonate and silica. Elevated carbonation temperature could promote the dissolution of fayalite in CS to enhance the carbon mineralization degree. Carbon mineralization treatment could improve the pozzolanic reactivity of CS and the 28 d strength activity index could reach up to 106.3%. The outcomes could help provide new technology to facilitate the resource utilization of CS.
Wang, Y., Li, X., Miao, W., Su, Y., He, X. Strnadel, B. (2024) The Carbon Mineralization Behavior of Copper Slag and Its Impact on Pozzolanic Reactivity. Cement and Concrete Composites.
Read the full paper here: The Carbon Mineralization Behavior of Copper Slag and Its Impact on Pozzolanic Reactivity I Cement and Concrete Composites
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Recent Trends in Anaerobic Digestion of Macroalgae for Blue Carbon Derived Biofuels - A Review
Abstract
Macroalgae, commonly known as seaweeds, are a major cultivated species in the aquaculture industry, and a key component in the food and pharmaceutical industries due to their hydrocolloid fraction. Recently, macroalgae have been revisited as marine-derived carbon donors or “blue carbon” donors due to their superior carbon sequestration potential and accessibility to human intervention in terms of climate change mitigation action. There is an ongoing debate on including macroalgae as “blue carbon” in addition to the conventional blue carbon sources, namely salt marshes, mangroves, and seagrass. Existing experimental evidence indicates that macroalgal carbon fixation is high next only to phytoplankton, and the fixed carbon is channeled via vertical and horizontal transport along with a considerable level of sink in sediments. Macroalgae are phylogenetically diverse, and based on their taxonomical position and morphological features, they are an attractive feedstock for biofuel production. This review assesses the potential of macroalgae as a feedstock for the production of biogas/biomethane. The role of the inherent biomass composition of biomethane in anaerobic digestion and other parameters influencing biogas yield are discussed. Commercial realization of macroalgal biomethane via life cycle assessment, techno-economic assessment, and exergy analysis, with future research outlook, is presented. Macroalgae present a potential marine-derived alternative compared to terrestrial carbon feedstock, and macroalgal biomethane is an untapped resource waiting to be explored.
Nagarajan, D., Senthilkurmar, G., Chen, C., Chang, J. & Dong, C. (2024) Recent Trends in Anaerobic Digestion of Macroalgae for Blue Carbon Derived Biofuels - A Review. Process Safety and Environmental Protection.
Read the full paper here: Recent Trends in Anaerobic Digestion of Macroalgae for Blue Carbon Derived Biofuels - A Review I Process Safety and Environmental Protection.