Carbon Sequestration Technologies Research Articles

Direct Electrocatalytic Conversion of CO2 to Chemicals over Single Atom Catalysts

Carbon dioxide emission from fossil fuel combustion has generated an on-going debate on its impact to the global environmental and ecological systems. New carbon capture, sequestration and conversion technologies are widely pursued as potential solutions to mitigate the concerns. The electrochemical CO2 reduction reaction (CO2RR) to hydrocarbon fuels and chemicals using renewable electricity offers an attractive “carbon-neutral” or even “carbon-negative” mitigation strategy. CO2 is an inexpensive carbon source and can be used as a feedstock for producing high value chemicals. Key challenges facing the current CO2RR electrocatalysis include: a) how to improve energy efficiency by reducing the overpotentials; b) how to increase the process selectivity by enhancing a single-product Faradaic efficiency (FE); and c) how to lower the system operating cost by prolonging the catalyst stability. Argonne National Laboratory through collaboration with Northern Illinois University recently developed a series of highly active and durable single atom catalysts (SACs) for CO2RR prepared using a robust synthesis method over the commercial carbon support. The new electrocatalysts offer the several advantages including: a) direct conversion to C2 (C2H5OH and CH3CO2H) and C3 (C3H6O) chemicals in one-step electro-catalytic reaction without secondary upgrading; b) higher than 90% FE by suppressing the byproduct formation; c) high energy efficiency with the onset potential as low as 0.4 V observed for ethanol conversion; and d) good stability with no sign of activity loss during extended hours of chronoamperometry measurement. In this presentation, we will discuss the structure-function relationship of the new SACs with particular emphasis on CO2 to ethanol conversion. We will also share the mechanistic insight on catalysis as the catalyst transitioning from SAC to metal cluster. The catalyst performance in terms of FE, onset potential and durability will also be reported, combined with the catalyst structural properties obtained from various conventional and advanced characterization tools. Acknowledgement: The work performed at Argonne National Laboratory is supported by Office of Science, U.S. Department of Energy under Contract DE-AC02-06CH11357.

Single-Atoms Synthesized Via a Novel Method As the Active Site with Highly Selectivity Electrocatalytic Conversion of CO2 to Ethanol

Single-atom catalysts (SACs) are recently emerging as a new frontier in heterogenous catalysis for their effectiveness in promoting catalytic reactions. We report herein the study of carbon-supported single-atom catalysts synthesized by a novelty method exhibit distinctive selectivity for some special electrochemical reactions during the electrolysis process. The aberration-corrected HAADF-STEM images combined with X-ray absorption spectroscopy identified the presence of single atoms. Theoretical density functional theory simulations of the best performing catalytic activity and selectivity could be attributed to the existence of single atoms in the catalysts. Introduction CO2 is a cheap resource of carbon that can be used as raw materials for fuel synthesis using renewable energy In 2005, 36.2 billion metric tons of CO2 was emitted to the atmosphere from anthropogenic sources, [1] which is corresponding to an increase in global mean temperature of around 0.1oC. New carbon capture, sequestration and conversion technologies are widely pursued as potential solutions to mitigate the concerns. The electrochemical CO2 reduction reaction (CO2RR) can combine carbon capture storage with renewable energy to convert CO2 into fuels and chemical feedstocks. Which is extraordinary significance for industry and is highly competitive with water electrolysis. Therefore, efficient electrocatalysts are required to reduce the reaction overpotential and improve the faradaic efficiency and selectivity for high value chemical products further. [2] The earth-rare, high price and low selectivity of precious metals prevent further large-scale commercial applications. Furthermore, these precious metal catalysts exhibit desirable products at highly cathodic potential window with high overpotential, which causes lot of energy consuming problem in application. Recently, single-atom catalysts (SACs) are emerging as a new frontier in heterogenous catalysis for their effectiveness in promoting catalytic reactions. [3] The unique electronic structure and unsaturated coordination environments in single atom catalysts (SACs) have been proven to enhance catalytic activity and excellent selectivity in a variety of reactions. In this work, the catalyst was prepared by a proprietary method currently under patent examination. Results and Discussion We report herein the study of carbon-supported SACs synthesized by a novel method that exhibit distinctive selectivity in electrochemical synthesis. The aberration-corrected HAADF-STEM images combined with X-ray absorption spectroscopy identified the presence of single atoms. Theoretical density functional theory simulations of the best performing catalytic activity and selectivity could be attributed to the existence of single atoms in the catalysts. The prepared metal single atoms dispersed on substrate catalysts showed high faradaic efficiency and selectivity of CO2 to C2 products conversion with low onset potential. Fig. 1a shows linear sweep voltammetry (LSVs) over M/C-0.1 before and after chronoamperometry measurements at different potentials. CV curves (Figure 1b) also displayed obvious activity toward CO2RR in the potential range from 0.5 V to -1.5 V vs RHE, and the current density remained stable with no apparent decay before and after electrolysis in CO2 saturated KHCO3 solution. The FE reached to as high as ~91.8% for ethanol at a low potential of -0.6 V when the metal loading is 0.1 wt% on carbon support. Figure 1. Electrochemical CO2RR over M/C-0.1. (a) LSV in a potential range of 0 to -1.5 V vs RHE in Ar and CO2 saturated 0.1 M KHCO3. (Scan rate: 50 mV s-1). (b) CV in a potential range of 0.5 to -1.5 V vs RHE in Ar and CO2 saturated 0.1 M KHCO3. (Scan rate: 50 mV s-1, (c) FEs of key byproduct as the function of potential over the catalysts of M/C-0.1 Significance Understanding the role of metal single atoms on the CO2 electrochemical reduction reaction is fundamental for design of an appropriated catalyst for the large-scale application of CO2 RR that aims the production of high energy liquid chemicals.

Stability of biochar and the mechanisms underlying its response to mineral modification: A review.

Biochar, with high degree of carbon stability, is considered as a kind of carbon sequestration material that can effectively alleviate the greenhouse effect. It is of great significance for carbon sequestration and mitigation to develop biochar with high carbon retention and stability. Mineral modification can regulate the stability of biochar. However, the relevant research has not received enough attention, and the underlying mechanism is not very clear. Firstly, the evaluation indices of biochar stability were summarized, mainly including H/C atomic ratio, O/C atomic ratio, coefficient of stability R50, volatile-matter content, thermal weight loss rate of carbon, carbon (chemical) oxidation loss rate, and cumulative CO2 emission of microbial mineralization. Then, based on the analysis of impact factors of biochar stability (such as raw material type, carbonization condition, external environment, etc.), we reviewed research progress about the effects of mineral modification on biochar stability. Furthermore, possible mechanisms of both enhancement and weakening effects on biochar stability were put forward. Enhancement is mainly due to the effects of physical barrier of minerals and the organic mineral complex formed by the interaction of mineral and biochar. While weakening effect is mainly due to special mineral composition, such as the Fe-bearing mineral composition, which promotes the thermal decomposition of biochar at high temperature. Finally, future research directions were proposed, in order to promote the development of carbon sequestration technology of biochar and provide technical support and theoretical basis for obtaining more stable biochar.

A novel technology of carbon dioxide adsorption and mineralization via seawater decalcification by bipolar membrane electrodialysis system with a crystallizer

Seawater carbon sequestration can not only reduce the greenhouse effect by carbon dioxide mineralization but also achieve seawater calcium removal. Generally, this process requires the addition alkaline reagents to make a high pH environment. This study developed a novel seawater carbon sequestration technology using a bipolar membrane electrodialysis system with a crystallizer. The results showed the new system had excellent synergistic effects. Water dissociation, CO2 adsorption and precipitation reactions between CO32− and seawater could be carried out in the system without the membrane contamination. With the electric-field, water dissociation occurred on the bipolar membrane and the alkalinity was used to enhance the absorption and ionization of CO2 in the chamber. Based on the ions selective mobility through the anionic membrane, weak base ions combined with seawater in the salt chamber. However, the cations in seawater, calcium and magnesium ions, could not pass through the anionic membrane, which prevented the pollution of the bipolar membrane. Meanwhile, the ion concentrations of CO32− was controlled and primary nucleation of CaCO3 could not occur in the salt chamber. The seeded crystallization in the crystallizer increased the reaction area and consumed the supersaturation degree of CaCO3. This study examined the effects of CO2 access mode of the membrane stack and the induced crystal seeds in the crystallizer on membrane fouling, seawater decalcification, carbon sequestration and energy consumption. This new system indicated the direction of bipolar membrane application in the adsorption and reactive crystallization of acid gas.

Recent developments and challenges ahead in carbon capture and sequestration technologies

Rapid industrialization and increasing trend of energy utilization resulted into exploitation of natural resources, i.e., fossil fuels, for power generation. This is resulting into addition of huge amount of carbon dioxide (CO2) as greenhouse gas into the environment. By year 2030, the primary production of energy from coal will reach to 3976 Mtoe and CO2 discharge of 38749 MtCO2 per year. In this review paper numerous aspects on carbon capture and sequestration (CCS) technologies have been compiled and discussed. The CO2 can be captured during fuel processing itself or after fuel combustion and transported to the sequestration site for long-term storage. A wide variety of the carbon separation and capture techniques including absorption into liquid, gas phase separation, and adsorption on solid and hybrid processes such as adsorption-membrane systems are discussed. In addition to this, the regulations for CCS, economic analysis and policy issues are addressed.

Enhancement of CO2 Absorption in Water through pH Control and Carbonic Anhydrase–A Technical Assessment

This paper provides an industrial-scale technical assessment of absorption of CO2 in water to react into bicarbonate (HCO3−), with the goal of storing HCO3− in the oceans as a carbon sequestration technology. A potential advantage of the process is that it will not require a CO2 transport and storage infrastructure that will be expensive for small-scale and remote emission sources. Process simulations are utilized to estimate absorber column length and for mass flow estimations of water and base required for a target capture rate of 90%. The results indicate that the process is technically feasible under specific conditions, with pH regulation being highly important, although the demand for base represents a limiting factor. Yet, a potential niche for the process is CO2 capture at smaller plants emitting small amounts of CO2.

Price for a good idea: $10,000

Students or young professionals can win a $10,000 prize to help realize an idea for reducing carbon emissions from industrial processes and products. Sponsors of the Carbon Footprint Challenge—including Covestro, Evonik Industries, and universities such as ETH Zurich and RWTH Aachen University—are looking for process efficiency, sustainable raw materials, and carbon sequestration technologies. Submissions are due in early July at carbonfootprintchallenge.org. The top five teams will get to pitch their ideas at an event in Zurich in early September.

Modeling, Simulation, and Optimization of Geological Sequestration of CO2

With heightened concerns on carbon dioxide (CO2) emissions from coal power plants, there has been a major emphasis in recent years on development of safe and economical geological carbon sequestration (GCS) technology. However, the detailed multiphase fluid dynamics and processes of GCS are not fully understood because various CO2 trapping mechanisms in geological formations have large variations in both spatial and temporal scales. As a result, there remain many uncertainties in determining the sequestration capacity of the reservoir and the safety of sequestered CO2 due to leakage. Furthermore, the sequestration efficiency is highly dependent on the CO2 injection strategy, which includes injection rate, injection pressure, and type of injection well, and its orientation, etc. The goal of GCS is to maximize the sequestration capacity and minimize the plume migration by optimizing the GCS operation. In this paper, first the basic fluid dynamics and trapping mechanisms for CO2 sequestration are briefly discussed. They are followed by a brief summary of current GCS projects worldwide with special emphasis on those in the United States. Majority of the paper is devoted to the numerical modeling, simulation, and optimization of CO2 sequestration in saline aquifers at macro spatial scales of a few to hundreds of kilometers and macro temporal scales of a few to hundreds of years. Examples of numerical simulations of a few large industrial scale projects are presented. The optimization studies include the investigation of various injection and well placement strategies to determine the optimal approach for maximizing the storage and minimizing the plume migration.

Sensitivity and Techno-Economic Analysis of Leading Oxy-Combustion Power Cycles with Full Carbon Capture: NetPower and Supercritical CES

The increasing concern on climate change has led to global efforts to reduce carbon dioxide (CO2) in the environment. It appears that by far the largest contribution to the greenhouse effect stems from emissions of carbon dioxide CO2. A large part of the CO2 emission are produced by the combustion of fossil fuels in conventional power plants and industrial processes. However, the Carbon Capture and Sequestration (CCS) technologies have been developed to minimise the CO2 emission to the atmosphere. Three main capture technologies (pre-combustion, post-combustion and oxy-fuel combustion) have been mainly developed for solid fuels (e.g., coal, biomass) combustion systems. However, there are many gas-fired power plants and industrial process burning natural gas as a cleaner fuel. Natural gas has the lowest CO2 emissions per unit of energy of all fossil fuels at about 14 kg C/GJ, compared to oil with about 20 kg C/GJ and coal with about 25 kg C/GJ. Although gas-fired plants emit less CO2 but still to achieve the environmental goals of the Paris Agreement it is essential to develop CCS technologies for the growing gas-fired systems. Among the available technologies, turbine-based oxy-combustion cycles (Oxyturbine cycles) are one of the most suitable carbon capture technologies for the gas-fired power plants. In this technology, natural gas is burned with pure oxygen, and temperature moderation is done by Flue Gas Recirculation (FGR) so that the exhaust gas includes mainly CO2 and water vapour ready for sequestration and storage. Recent developments in oxy-combustion technology have reduced the cost of capture and made it competitive with post- combustion technology. Several oxyturbine cycles have been introduced by means of thermodynamic analysis. However, only NetPower and Supercritical CES cycles have recently proceeded to the demonstration phase. The NetPower cycle recirculates only carbon dioxide as the working fluid, and the Supercritical CES cycle uses water as its working fluid. The Supercritical CES cycle that has best efficiency among other type of CES cycles includes high, medium and low-pressure turbines (HP, MP, and LP) and the exhaust gas from the high-pressure turbine is reheated and expanded in an MP and LP. Pure oxygen is produced in an Air Separation Unit (ASU) and directly inject into the combustion chamber. The NetPower cycle includes a single turbine with high inlet pressure and a main multi-stream heat exchanger. Pure oxygen is produced in the ASU and mixed with the recycled carbon dioxide, before being introducing to the combustion chamber. Both cycles include recycling loops and carbon dioxide purification sections. These novel cycles reduce the cost for power generation with complete CO2 capture and sequestration with nearly zero emission. In this paper, The NetPower and Supercritical CES Cycles are investigated by means of process simulation and the technologies and utilised facilities compared using sensitivity analysis. Both cycles are simulated with Aspen Plus software with the same initial conditions, and the simulation results are compared with IEA 2015 report for validation. The sensitivity of both cycles are analysed with respect to the Turbine Inlet Temperature (TIT), Combustion Outlet Pressure (COP) and Heat Exchanger Approach Temperature (HET). The efficiencies are extracted for both the NetPower and CES cycles, and partial load behaviour of the cycles are investigated. The initial results show that the NetPower cycle is more sensitive to the Turbine Inlet Temperature (TIT) variations in comparison with S-CES cycle. The results of this paper provide a platform for a comprehensive techno-economical and sensitivity analysis of the NetPower and Supercritical CES Cycles as the leading Oxy-combustion power cycles with full carbon capture.

Biophysical model and techno-economic assessment of carbon sequestration by microalgal ponds in Indian coal based power plants

The present study evaluated the carbon dioxide (CO2) sequestration potential of Thalassiosira pseudonana using the influencing key climatic datasets of an Indian coal based power plant through a biophysical energy balance model developed on MATLAB platform with ODE45s solver. The maximum average areal biomass productivity was predicted to be 111.39 kg ha−1d−1 with maximum growth in February, leading to the CO2 capture of 147.03 kg ha−1d−1. Further, techno-economic analysis was performed utilizing the results of the formulated biophysical model to access the process feasibility using SuperPro designer. Results revealed the technical viability and economic feasibility of the process, with the unit production price of 58.41 $ per ton with a reasonable rate of returns and acceptable short payback time of 2.81 years. A yearly carbon credits of 52 M$ could be earned by the company. Sensitivity analysis showed the process to be highly dependent over the raw material prices and facility operation. The integrated site-specific biophysical model and economic analysis are essential to provide reliable realistic estimates of the algal carbon sequestration technology that could drive the energy policies towards sustainable development.

Overview of Carbon Capture Technology: Microalgal Biorefinery Concept and State-of-the-Art

The impending danger of climate change and pollution can now be seen on the world panorama. The concentration of CO2, the most important Green House Gas (GHG), has reached to formidable levels. Although carbon capture and storage (CCS) methods have been largely worked upon, they are cumbersome in terms of economy and their long term environmental safety raises a concern. Alternatively, bio-sequestration of CO2 using microalgal cell factories has emerged as a promising way of recycling CO2 into biomass via photosynthesis which in turn could be used for the production of bioenergy and other value-added products. Despite enormous potential, the production of microalgae for low-value bulk products and bulk products such as biofuels, is heretofore, not feasible. To achieve economic viability and sustainability, major hurdles in both, the upstream and downstream processes have to be overcome. Recent technoeconomic analyses and life-cycle assessments of microalgae-based production systems have suggested that the only possible way for scaling up the production is to completely use the biomass in an integrated biorefinery set-up wherein every valuable component is extracted, processed and valorized. This article provides a brief yet comprehensive review of the present carbon sequestration and utilization technologies, focusing primarily on biological CO2 capture by microalgae in the context of bio-refinery. The paper discusses various products of microalgal biorefinery and aims to assess the opportunities, challenges and current state-of-the-art of microalgae-based CO2 bioconversion, which are essential to the sustainability of this approach in terms of the environment as well as the economy.

Carbon capture and sequestration potential in India: A comprehensive review

Concerns due to anthropogenically forced climate change owing to emissions of CO2 are now well accepted and have resulted in several initiatives to reduce CO2 emissions. The U.N. panel (IPCC) in its latest report indicated that to contain warming at 1.5 °C, manmade global net CO2 emissions would need to fall by about 45 % by 2030 from 2010 levels and reach ‘net zero’ by 2050. Carbon capture and sequestration (CCS) technology is a process of capturing waste CO2 from large point sources, such as fossil fuel stations, so that it will not enter the atmosphere. CCS is seen a crucial climate protection technology for coal-rich countries like India having potential in massively reducing CO2 emission as compared to any other existing technology. As third largest producer of coal and fourth largest greenhouse gas (GHG) emitter, India’s total emissions are 7% of global emissions and is increasing at 4.5% per annum. India’s current and expected future emissions are sufficiently massive to have an adverse effect on global mitigation efforts. The IPCC studied that without CCS, the price of achieving long-run climate goals is almost 140% more expensive. However, India has been taking a cautious approach towards CCS technology due to various factors. The paper discusses on the challenges of CCS in India and a roadmap for the successful implementation of CCS in India.

Exploration and Practice of Carbon Sequestration Realized by CO2 Waterless fracturing

Carbon sequestration is an important measure to reduce greenhouse gas emissions. This paper introduces a new method of carbon sequestration using CO2 waterless fracturing technology. Based on the supporting technology system with independent intellectual property rights, waterless fracturing field tests were carried out on 19 wells in Jilin oilfield. The on-site monitoring data shows that CO2 stays in a supercritical state for a long time in the process of waterless fracturing, soaking and flowback, which is favourable for carbon sequestration. The geological model of H87 test area was established to simulate and evaluate CO2 recovery after fracturing. The results show that the storage ratio of CO2 waterless fracturing is 76.46%. Meanwhile, the production after waterless fracturing is 2.4 times that after water-based fracturing with the same scale, and the average single well operation saves 1512 m3 water. It can be seen that CO2 waterless fracturing is a new type of carbon sequestration technology with high storage efficiency, good stimulation effect, significantly reduction of water consumption during oil and gas reservoir development and has broad market prospects.

Predicting soil carbon saturation deficit and related properties of New Zealand soils using infrared spectroscopy

Conversion of soils supporting native vegetation to agricultural production has led to a loss of soil carbon stocks. Replacing a portion of the lost stocks will sequester atmospheric carbon with the concurrent benefit of enhancing soil sustainability. The ability of the fine fraction of soils (≤50-µm fraction) to adsorb organic carbon (OC) is considered a key mechanism capable of stabilising soil OC against loss. The difference between the current and maximum concentrations of OC in the soil fine fraction (FFC) has been termed the ‘saturation deficit’ (SatDef) and used to define the potential for a soil to sequester carbon. For New Zealand surface 0–15 cm soil layers, pedotransfer functions have been derived to quantify the soil carbon SatDef. The ability of combining infrared spectroscopy (IR) with partial least squares regression (PLSR) to derive predictive algorithms for soil properties included in these pedotransfer functions, the capacity of the soil fine fraction to stabilise carbon and the SatDef of the soil fine fraction were assessed in this study. A total of 168 air-dried and finely ground New Zealand surface soils representative of the major soil orders used for agricultural production were included. Principal components analysis of IR spectra showed a grouping by soil order that was related to mineralogy. Predictive IR/PLSR algorithms were derived for specific surface area, pyrophosphate-extractable aluminium, the FFC content, the 90th quantile regression of FFC and the SatDef of the fine fraction (R2 values ≥0.85; ratio of performance to interquartile range values ≥2.9). The results indicate that IR/PLSR provides a rapid and cost-effective mechanism for deriving information related to the amount of FFC in soils and the SatDef of the fine fraction. The IR/PLSR approach could be used to define the potential of soils to sequester carbon and identify the soil types to target for carbon sequestration technologies. The approach would also generate valuable data for soil carbon in national inventories or national soil condition monitoring programs.

Techno-economic and environmental analyses of a novel, sustainable process for production of liquid fuels using helium heat transfer

In this paper, several new processes are proposed which co-generate electricity and liquid fuels (such as diesel, gasoline, or dimethyl ether) from biomass, natural gas and heat from a high temperature gas-cooled reactor. This carbonless heat provides the required energy to drive an endothermic steam methane reforming process, which yields H2-rich syngas (H2/CO > 6) with lower greenhouse gas emissions than traditional steam methane reforming processes. Since downstream Fischer-Tropsch, methanol, or dimethyl ether synthesis processes require an H2/CO ratio of around 2, biomass gasification is integrated into the process. Biomass-derived syngas is sufficiently H2-lean such that blending it with the steam methane reforming derived syngas yields a syngas of the appropriate H2/CO ratio of around 2. In a prior work, we also demonstrated that integrating carbonless heat with combined steam and CO2 reforming of methane is a promising option to produce a syngas with proper H2/CO ratio for Fischer-Tropsch and methanol/dimethyl ether applications. In this study, we presented another novel design called gas-nuclear-to-liquids process which can be applied for liquid fuel production without needing H2/CO adjustment. Chemical process simulations of several candidate processes were developed, which used the rigorous multi-scale, two-dimensional, heterogeneous models for the carbonless-heat-powered steam methane reforming and mixed reforming of methane processes developed in prior works in gPROMS. In addition, 1D process models within Aspen Plus were also used (Aspen Plus simulation and gPROMS models are provided to the reader). The performance of the presented systems was compared with a biomass-gas-to-liquids plant where heat from gasification drives the steam methane reforming instead of the high temperature gas-cooled reactor. Techno-economic analyses and greenhouse gas life cycle analyses of each case were completed to investigate the economic and environmental impacts of the proposed processes. Optional carbon capture and sequestration technology is also considered. The analysis demonstrates that carbonless heat integration leads to thermal efficiencies of up to 55% (high heating value based) as well as suitable profits in the right market conditions. It is also found that net negative life cycle greenhouse gas emissions of the final products can be achieved owing to use of biomass, carbonless heat, and carbon capture and sequestration. Even without carbon capture and sequestration, the life cycle greenhouse gas emissions of the proposed process are 25–57% lower than traditional natural gas-to-dimethyl ether and coal-to- dimethyl ether processes.

Experimental and numerical analysis of non-premixed oxy-combustion of hydrogen-enriched propane in a swirl stabilized combustor

Oxyfuel combustion is a promising carbon capture and sequestration technology. The use of CO2 diluent in oxyfuel combustion can lead to flame instability. In this study, the effect of hydrogen enrichment on the blowout limits of propane oxyfuel flames under CO2 dilution was analyzed experimentally and numerically in a swirl-stabilized, non-premixed combustor. Results show that increasing the hydrogen concentration from 0 to 30% extends the blowout limits of the CO2 diluted oxyfuel flames by 2.5%. Hydrogen enrichment, however, was found to increase CO while lowering CO2 emission as a consequence of the low residence time and competition for oxygen between the fuel species. In this regard, the minimum amount of CO2 emission recorded (74.3%) corresponds to a maximum CO emission of (1.93%) at hydrogen concentration of 40%. Increasing the gases residence time in the combustor lowers the CO emission which is desirable since beyond certain limit, CO in exhaust gases can promote the formation of pentacarbonyls that can damage CO2 transportation pipelines aimed at CCS. Decreasing the equivalence ratio from 1.0 to 0.9 also leads to a significant reduction in CO emission from 8000 ppm to <1 ppm. The flames, however, display better stability at higher equivalence ratios.

Solubilities of CO2 capture absorbents methyl benzoate, ethyl hexanoate and methyl heptanoate

Abstract Carbon capture, utilization and sequestration technology is effective for carbon emissions reduction. The development of new absorbent seems to be one of the core components of carbon capture technology. In this paper, three esters, methyl heptanoate, ethyl hexanoate and methyl benzoate, were selected to determine CO2 solubilities at different temperatures ranging from 293.15 to 333.15 K, and pressures up to 1.2 MPa, using the isothermal synthesis method. The results showed that the absorbent with the straight-chain alkyl group was more effective for improving CO2 absorption capacity than the benzene group. Ethyl hexanoate showed slightly higher CO2 solubilities than its isomer methyl heptanoate. In addition, Henry’s constant and thermodynamic properties such as solution enthalpy, solution entropy, solution Gibbs energy and solution heat capacity, were determined based on the measured data since the above properties are essential for designing an absorption process. Ethyl hexanoate is superior to the other two selected absorbents, common solvents, commercial absorbents, some physical absorbents, some polymeric absorbents and some ionic liquids, which indicates that it has potential value for CO2 capture technology. However, further studies will be necessary to assess the reliability of its industrial application.

Economic optimisation of European supply chains for CO2 capture, transport and sequestration, including societal risk analysis and risk mitigation measures

European large stationary sources are currently emitting more than 1.4 Gt of CO2 every year. A significant decrease in greenhouse gases emissions cannot be achieved without carbon capture and sequestration (CCS) technologies. However, although being practiced for over 30 years, CO2 transportation is intrinsically characterised by the risk of leakage. This study proposes to assess and tackle this issue within the CCS design problem, by proposing a spatially explicit mixed integer linear programming approach for the economic optimisation of a European supply chain for carbon capture, transport and geological storage, where societal risk assessment is formally incorporated within the modelling framework. Post-combustion, oxy-fuel combustion and pre-combustion are considered as technological options for CO2 capture, whereas both pipelines (inshore and offshore) and ships are taken into account as transport means. Both inland-inshore and offshore injection options are available for carbon geological sequestration. Risk mitigation measures are considered in the design of the transport network. The overall supply chain is economically optimised for different minimum carbon reduction scenarios. Results demonstrate that accounting for societal risk may impact the overall carbon sequestration capacity, and that the proposed approach may represent a valuable tool to support policy makers in their strategic decisions.

The Effect of the Agricultural Carbon Sequestration and Agrochemical Reduction on the Regional Water Environment Quality

This paper analysed the impact of the agricultural carbon reduction and emission reduction measures implementation on the environmental quality of surface water and groundwater in winter and summer in Henan and Anhui Province project areas by using entropy weight fuzzy matter element analysis method. The result showed that the reduction in the application of chemical fertilizers and pesticides had a certain impact on the improvement of the water environment by using agricultural carbon sequestration technologies.

Near-term deployment of carbon capture and sequestration from biorefineries in the United States

Capture and permanent geologic sequestration of biogenic CO2 emissions may provide critical flexibility in ambitious climate change mitigation. However, most bioenergy with carbon capture and sequestration (BECCS) technologies are technically immature or commercially unavailable. Here, we evaluate low-cost, commercially ready CO2 capture opportunities for existing ethanol biorefineries in the United States. The analysis combines process engineering, spatial optimization, and lifecycle assessment to consider the technical, economic, and institutional feasibility of near-term carbon capture and sequestration (CCS). Our modeling framework evaluates least cost source-sink relationships and aggregation opportunities for pipeline transport, which can cost-effectively transport small CO2 volumes to suitable sequestration sites; 216 existing US biorefineries emit 45 Mt CO2 annually from fermentation, of which 60% could be captured and compressed for pipeline transport for under $25/tCO2 A sequestration credit, analogous to existing CCS tax credits, of $60/tCO2 could incent 30 Mt of sequestration and 6,900 km of pipeline infrastructure across the United States. Similarly, a carbon abatement credit, analogous to existing tradeable CO2 credits, of $90/tCO2 can incent 38 Mt of abatement. Aggregation of CO2 sources enables cost-effective long-distance pipeline transport to distant sequestration sites. Financial incentives under the low-carbon fuel standard in California and recent revisions to existing federal tax credits suggest a substantial near-term opportunity to permanently sequester biogenic CO2 This financial opportunity could catalyze the growth of carbon capture, transport, and sequestration; improve the lifecycle impacts of conventional biofuels; support development of carbon-negative fuels; and help fulfill the mandates of low-carbon fuel policies across the United States.