Carbon-neutral Technologies Research Articles

European ports transition to carbon-neutral energy: A multiple regression analysis

This paper focuses on sustainable initiatives in the maritime industry, specifically energy transition in EU ports. Our research aims to apply the stakeholder theory in port contexts, to examine the influence of different actors on the adoption of carbon–neutral energy generation technologies, from a port-employee perspective. To that aim, the proposed conceptual model is empirically tested through a survey among port employees, following the identification of applicable technologies via a literature review. Specifically, six types of energy generation technologies that advance the goal of carbon neutrality are identified, and likewise, following the stakeholder theory approach, we identified six categories of relevant stakeholders, perceived as external or internal. By means of a multiple regression analysis, we assess the influence of stakeholders identified regarding the carbon–neutral generation technologies. The results corroborate the suitability of the stakeholder approach for assessing port environments. The findings suggest the existence of different perceptions among port employees regarding the various technologies, while stakeholder influence can be either positive or negative depending on the type of technology. Among the stakeholders involved, customers and competitors appear as most influential. The main contribution of our results derive of tackling the differences in perception of carbon neutrality within the European Ports, and the carbon–neutral technologies in ports contributing towards carbon neutrality. By providing a more thorough understanding regarding the influence of diverse stakeholders in promoting carbon neutral energy generation technologies, this study can serve as a guideline for future research and be of value for practitioners in the field.

Global trends in the investment policy of countries in agriculture in the context of transition towards renewable energy sources

Relevance. The renewable energy sector is attractive for foreign direct investment, among which projects related to the introduction of wind energy, as well as the reproduction of energy from biomass and biofuels are popular with investors. The proof of the popularity of such projects is the investment of 70% of all investments in renewable energy sources.The purpose The aim is to consider the trends of global investments in agriculture in the context of the transition to renewable energy sources.Objectives: to analyze the inflow of FDI to various regions of the world for the implementation of renewable energy transition projects; to show the reasons for the uneven investment of countries in different regions in modern conditions.Methodology. The structural theory is used to study investment flows, and the method of studying statistical reporting according to UNCTAD and CEPAL data is used for quantitative and qualitative analysis of attracted investments.Results. The statistical data used formed the basis for a quantitative and qualitative analysis of the directions of attracting FDI to various countries, showing the heterogeneity of this process by region. The global climate situation requires accelerating low-carbon innovation by all possible means. Developed countries have the same problems of transition to renewable energy as developing countries, so investment investments are relevant for agriculture in all regions of the world.Conclusions. Western countries prefer to be in the trend of the modern economy and invest in green sectors of the economy and those industries that use carbon-neutral technologies. Global changes in green energy financing related to the transfer of funds to the "hotbeds of conflict" in Ukraine and the Middle East have put some countries (LACs) in need of finding their own resources to continue energy transition projects.

Does Scaling Up Pig Farming Promote Carbon Neutrality Among Pig Farmers?

Pig farming is a major source of carbon emissions in China's livestock industry, and the promotion and application of carbon neutral technologies dedicated to carbon reduction and sequestration is a key measure to promote the realization of carbon neutrality in pig farming industry. In the absence of a system for carbon emission reduction in agriculture, it is important to explore whether large-scale pig farming can spontaneously promote the application of carbon neutral technologies by pig farmers. Combined with the technical background of carbon neutrality in pig farming industry and using the field survey data of 468 pig farmers in Shandong Province, this paper empirically analyzed the effect of large-scale pig farming on the carbon neutral behavior of pig farmers. The findings are threefold. Firstly, because of the effect of economies of scale in the application of carbon neutral technologies, large-scale pig farming can promote the carbon neutral behavior of pig farmers. However, the effect of economies of scale in the application of carbon neutral technologies has a boundary, and the annual output of pigs should be maintained at 3000 to 4999. Secondly, among the effects of pig breeding scale on the application and its degree of composting project, state of planting and breeding cycle has no regulating effect. Thirdly, among the effects of pig breeding scale on the application and its degree of biogas engineering, both state of planting and breeding cycle and subsidy for construction of biogas digester have negative regulating effects. In this paper, the pig farming industry is taken as a typical example to reveal the endogenous incentive mechanism of promoting agricultural carbon emission reduction, which provides theoretical reference and experience enlightenment for the formulation of effective policies to promote agricultural carbon neutrality, which are different from industrial industries.

Intermittent Electrification with Battery Locomotives and the Post-Diesel Future of North American Freight Railroads

Changing attitudes, regulations, public policy, and international treaties concerning fossil fuels are likely to lead freight railroads toward carbon-neutral technologies, yet only electric traction matches the performance of diesel-electric locomotives. The tremendous power requirements of freight trains make efforts to reduce greenhouse gas (GHG) emissions challenging, but the prospect of 7.2 megawatt-hour battery-electric locomotives (BELs) offers promise, and intermittent electrification can facilitate battery charging. Train performance calculations under simulated real-world conditions show four 7.2 megawatt-hour BELs can power 8,000-ton trains up to 230 mainline miles unassisted, with average energy consumption of 12.5 watt-hours/ton-mile. This permits discontinuous electrification of major freight lines, leaving “gaps” of up to 200 mi to reduce capital costs, especially in rugged terrain or where the power grid is sparse. Massive onboard battery arrays and intermittent access to the electrical grid for traction power and recharging provide great energy savings by recycling energy now lost when traveling downhill or braking. A case study of a hypothetical Class I railroad found intermittent electrification with BELs more than 60% more cost-effective than contiguous electric districts, and dramatically reduced engine changes. To reduce railroad GHG emissions, governments must support technical development, show that electrification works in various North American settings, and develop institutional-financial frameworks to incentivize intermittent electrification with BELs, all in the context of massive environmental and capacity upgrades to electrical networks. Given proper assistance and incentives, early 21st century railroads may find discontinuous overhead-wire electrification offers great promise in operating terms.

Sustainable fabrication of solvent resistant biodegradable cellulose membranes using green solvents

The paradigm of the polymer industry is confronting an inevitable transition from fossil-based to bio-derived sources. The membrane-based separation process, generally regarded as a sustainable technology, mostly employs fossil-based polymeric membranes. In order to become an entirely carbon–neutral technology, all of the materials and chemicals employed during membrane fabrication must be scrutinized from a sustainability perspective. In this work, we report a versatile strategy to fabricate solvent-resistant cellulose membranes using bio-derived green solvents. The thermodynamic and kinetic aspects of the membrane fabrication process were systematically investigated. It was found that well-known green solvents such as Cyrene and PolarClean were not suitable due to high dope viscosity, whereas bio-derived methyl lactate and triethyl phosphate exhibited desirable properties to yield excellent cellulose membranes. The membrane performance could be tailored from the ultrafiltration to nanofiltration range by controlling the fabrication parameters. Importantly, the thermal treatment step prior to the deacetylation reaction was necessary to improve the solute rejection profile. The cellulose membranes displayed adequate compression resistance against pressure. However, their shear resistance was insufficient compared to that of commercial membranes. Nevertheless, the prepared cellulose membranes exhibited excellent solvent resistance in strong aprotic solvents such as N-methylpyrrolidone and N,N-dimethylacetamide, potentially allowing them to enter niche membrane markets such as the organic solvent nanofiltration (OSN).

Sustainable energy transition optimization through decentralized hybrid energy systems with various energy storage technologies under multi-criterion indices: A mid-career repowering scenarios

Sustainable energy transition (SET) refers to the formulation of effective policies for quantifying the paradigm shift from fossil fuels to carbon-neutral technologies. Despite the anticipation of sustainable solutions, many developing nations continue to experience unsustainable energy regimes. Understanding the potential of this transition demands a multifaceted approach, emphasizing techno-economic optimization and performance enhancement to address future decentralized energy constraints. Although one of several ways to enable SET, the consideration of renewable energy sources (RESs) coupled with energy storage technologies (ESTs), which can offer multi-dimensional decision flexibility in present energy policies, is quite restricted. Based on a comparative analysis of various ESTs, this paper provides insight exploration of the SET framework by leveraging a diverse range of renewable potentials. Utilizing a proprietary derivative-free algorithm (PDFA) and an original grid-search algorithm (OGSA), the study focuses on load forecasting across different time horizons using a real-time dataset from multiple load centers in Pakistan. Load forecasting is carried out based on a combination of seasonal naïve forecasting (SNF), seasonal and trend decomposition using loess forecasting (STLF), and artificial neural networks (ANN). Results reveal a minimum Levelized cost of energy (LCOE) ranging from $0.105/kWh to $0.109/kWh in the presence of solar and dispatchable renewable-based hybrid configurations. For battery ESTs, based on NPC and LCOE, the feasibility is observed in the order of lead-acid (La), lithium-ion (Li-ion), and vanadium redox flow (VRF) technology. From a technical and capacity shortage fraction (CSF) perspective, Li-ion performed better than both La and VRF in terms of storage depletion as well as annual losses. Finally, a mid-career repowering analysis examines the behavior of energy storage technologies (ESTs), while sensitivity analyses and results validation highlight the significance of the proposed study's findings.

Armoring hydrophilic wood-structured ultrathick electrode with bimetallic nitride enables high energy-density supercapacitor

Thick electrodes can reduce the ratio of inactive constituents in a holistic energy storage system while improving energy and power densities. Unfortunately, traditional slurry-casting electrodes induce high-tortuous ionic diffusion routes that directly depress the capacitance with a thickening design. To overcome this, a novel 3D low-tortuosity, self-supporting, wood-structured ultrathick electrode (NiMoN@WC, a thickness of ∼1400 μm) with hierarchical porosity and artificial array-distributed small holes was constructed via anchoring bimetallic nitrides into the monolithic wood carbons. Accompanying the embedded NiMoN nanoclusters with well-designed geometric and electronic structure, the vertically low-tortuous channels, enlarged specific surface area and pore volume, superhydrophilic interface, and excellent charge conductivities, a superior capacitance of NiMoN@WC thick electrodes (∼5350 mF cm−2 and 184.5 F g−1) is achieved without the structural deformation. In especial, monolithic wood carbons with gradient porous network not only function as the high-flux matrices to ameliorate the NiMoN loading via cell wall engineering but also allow fully-exposed electroactive substance and efficient current collection, thereby deliver an acceptable rate capability over 75% retention even at a high sweep rate of 20 mA cm−2. Additionally, an asymmetric NiMoN@WC//WC supercapacitor with an available working voltage of 1.0–1.8 V is assembled to demonstrate a maximum energy density of ∼2.04 mWh cm−2 (17.4 Wh kg−1) at a power density of 1620 mW cm−2, along with a decent long-term lifespan over 10,000 charging-discharging cycles. As a guideline, the rational design of wood ultrathick electrode with nanostructured transition metal nitrides sketch a promising blueprint for alleviating global energy scarcity while expanding carbon-neutral technologies.

Nano zero-valent iron functioned 3D printing graphene aerogel electrode for efficient solar-driven biocatalytic methane production

To address the urgent need for developing carbon-neutral technologies, microbial electrosynthesis (MES), as an important contributor to the renewable energy field, can convert carbon dioxide to multi-carbon chemicals using microbes serving as living catalysts at the cathode. However, the performance of the cathode is restricted by the weak electrochemical reaction kinetics of the organisms, the specific area of the electrode, and the mass transfer under high current. Herein, we report a facile 3D-printed graphene aerogel (GA) electrode built with a nanozero-valent iron (NZVI)-functionalized graphene ink. The 3D-printed GA electrode was designed to possess hierarchical pores with an enhanced high specific surface area for microbial colonization while ensuring mass transfer. NZVI can assist in-situ hydrogen generation, facilitating biofilm formation and methane (CH4) production in the indirect electron transfer pathway. Consequently, the optimized 3D-printed electrode achieved a maximum CH4 production rate of 6993 ± 832 mmol/m2/d with a faradaic efficiency of 83.7%, which increased by 3.24-fold to the carbon felt electrode. In addition, integrating the proposed cathode into a PV-electrolyzer cell yielded a solar-to-CH4 efficiency of 4.70%. This study provides a unique method for the development of advanced cathodes and underscores the potential of integrating MES with renewable energy technologies.

Durable CO2 conversion in the proton-exchange membrane system.

Electrolysis that reduces carbon dioxide (CO2) to useful chemicals can, in principle, contribute to a more sustainable and carbon-neutral future1-6. However, it remains challenging to develop this into a robust process because efficient conversion typically requires alkaline conditions in which CO2 precipitates as carbonate, and this limits carbon utilization and the stability of the system7-12. Strategies such as physical washing, pulsed operation and theuse of dipolar membranes can partially alleviate these problems but do not fully resolve them11,13-15. CO2 electrolysis in acid electrolyte, where carbonate does not form, has therefore been explored as an ultimately more workable solution16-18. Herein we develop a proton-exchange membrane system that reduces CO2 to formic acid at a catalyst that is derived from waste lead-acid batteries and in which a lattice carbon activation mechanism contributes. When coupling CO2 reduction with hydrogen oxidation, formic acid is produced with over 93% Faradaic efficiency. The system is compatible with start-up/shut-down processes, achieves nearly 91% single-pass conversion efficiency for CO2 at a current density of 600 mA cm-2 and cell voltage of 2.2 V and is shown to operate continuously for more than 5,200 h. We expect that this exceptional performance, enabled by the use of a robust and efficient catalyst, stable three-phase interface and durable membrane, will help advance the development of carbon-neutral technologies.

Flow-field design of the bipolar plates in polymer electrolyte membrane fuel cell: Problem, progress, and perspective

As a promising carbon-neutral technology, the polymer electrolyte membrane fuel cell (PEMFC) is gaining considerable attention over the past decades. Many problems in PEMFC performance and durability can be ultimately ascribed to the flow-field design, which is a complex and systematic work owing to the inherent sophisticated nature of the PEMFC with multicomponent mass transportation and multiphysics field coupling. This paper presents a critical review of the state-of-the-art flow-field designs and an in-depth analysis of the key problems involved from a perspective of efficient mass transport within the PEMFC. In particular, flow-optimization principles are discussed specifically for the enhancement in reactant mass transfer, water management, optimized opening ratio, uniformity of flow distribution, and choice of appropriate numerical approaches assisting the flow-field design. The material formability and forming accuracy and their effects are also discussed for metallic bipolar plates. The objective of this review work is to present a comprehensive overview of the problems, progresses, and perspectives of the flow-field designs for bipolar plates in PEMFC and provide a general theoretical instruction for present and future relevant R&D activities that aim at high-performance, durable, and low-cost fuel cells.

Quality Improvement Effect of Waste Concrete Fine Powder by Applying Exfoliation Technology

Since the main components of waste concrete fine powder generated in the process of converting waste concrete into recycled aggregate are essentially the same as the main ingredients of cement-clinker, it is possible to use it as a raw material for cement. In addition, because waste concrete fine powder is a decarbonated salt, using it as a raw material for cement clinker is a very important carbon-neutral technology that can be expected to reduce process-derived carbon emission generated during cement manufacturing. However, waste concrete fine powder has a low calcium oxide content of around 10%, so its usability as a clinker raw material is very low. In order to use waste concrete fine powder as a raw material for clinker, the calcium oxide content must be increased to more than 35%. Separating the hardened cement paste from the aggregate while reducing the crushing ration of the aggregate during the crushing process is an important means of increasing the calcium oxide content of waste concrete fine powder. Accordingly, this study conducted an experimental study to increase the calcium oxide content of waste concrete fine powder using exfoliation grinding technology. The characteristics of waste concrete fine powder recovered through the exfoliation grinding technology were examined for waste concrete collected from a domestic intermediate processing company, model concrete manufactured in a laboratory, and commercially available cement bricks. As a result of the experiment, it was possible to recover the waste concrete fine powder with a higher CaO content by applying exfoliation grinding technology, compared to the dust collection fine powder that could be recovered through the crushing and grinding process.

Levelized-cost optimal design of long-distance CO2 transportation facilities

With the need to develop carbon-neutral technologies and reduce greenhouse gas emissions to avert climate change, carbon capture, storage and utilization (CCS/CCUS) techniques have emerged as effective pathways to achieve these targets. Despite being a critical aspect of CCS/CCUS chains, carbon dioxide transport is an astonishingly under-researched domain. This study presents an efficient and robust computational model to cost-optimally design of long distance carbon dioxide transport pipelines (trunk) connecting a source-sink pair. Several physical and topographical conditions have been accounted for to propose optimal design solutions for different case studies. This involves right-sizing of pipes and booster stations and placing the latter at the right locations. The implications of uncertainties in modelling of the costs have also been studied. The model is very flexible and general in the sense that it can work with a variety of cost models and design constraints. Further, unlike most studies, an appropriate hydrodynamic model for pressure and density calculations has been incorporated. Genetic algorithm and interior point methods have been employed to find optimal design parameters that minimize the “per ton levelized transportation cost”, and their performances have been compared. Results demonstrate that pipe diameters and elevation changes have the most significant impact on the pressure drop, optimal design parameters and the cost. Lastly, several improvements have been made over our previous study in this domain.

Research on energy efficiency and decarbonization pathway of nearly zero energy buildings based on system dynamic simulation

Accounting for over 40% of the total energy consumption, the global building sector is pivotal for achieving carbon peak and neutrality objectives. The intricate nature of building carbon emissions, influenced by spatial, temporal, and multifactor coupling, poses challenges on implementing carbon-neutral technologies and conservation strategies. This study focuses on nearly zero energy buildings in China and employs system dynamics to predict energy consumption and carbon emissions according to various scenarios, unveiling influencing patterns and viable emission reduction pathways. The results highlight the substantial impact of enhancing energy conservation awareness as this leads to a 36.4% reduction in energy consumption and a 44.2% reduction in carbon emissions. To attain energy efficiency and carbon reduction goals, a comprehensive approach is essential, encompassing improved building performance, heightened resident energy awareness, increased renewable energy use, and energy landscape adjustments. These findings inform future building energy and carbon emission regulations and offer valuable policy insights.

Methane dehydroaromatization process in a carbon-neutral strategy

Methane dehydroaromatization (MDA) process is a “non-oxidative” technology for CH4 utilization, esteemed as a propitious substitution for fossil fuel-based counterparts in the synthesis of benzene, toluene, and xylene (BTX). However, the MDA process is less cost-effective than both commercial BTX production and “oxidative” CH4 conversion technologies, primarily due to its inherently low BTX yield and CH4 conversion rate. As the focus on attaining net-zero emissions escalates and concerns regarding the usage of abundant CH4 arise, the MDA process has emerged as an environmentally efficient alternative that can generate high-value products while decreasing direct CO2 emissions. In this study, we evaluate various MDA reaction systems, including MDA utilizing only pure CH4, additive co-feeding MDA, and hydrocarbons co-feeding MDA, employing a Mo/HZSM-5 catalyst. The proposed process design comprehensively analyzes the impact of MDA reaction systems on product distribution and energy consumption. Furthermore, we confirm the feasibility of the proposed MDA processes through an exhaustive environmental and economic assessment of “oxidative” CH4 conversion methods and commercial BTX production processes. By decentralizing some of the immense direct CO2 emissions from existing CH4 utilization to controllable indirect CO2 emissions, the MDA processes prove to be more advantageous under the net-zero strategy. The results of this analysis reinforce the potential of MDA reaction processes as a carbon-neutral technology that can effectively replace oxidative CH4 conversion while producing high-value products.

Efficient reduction of CO2 to C2 hydrocarbons by tandem nonthermal plasma and photocatalysis

CO2 photoreduction to hydrocarbons is a carbon-neutral technology for renewable energy. However, this strategy is challenged by the thermodynamic stability of CO2 and the low efficiency of multi-photoelectron utilization. In this paper, tandem nonthermal plasma and photocatalysis were used to effectively improve the efficiency of CO2 reduction to C2. We first activated CO2 by nonthermal plasma technology (NTP) and then converted the activated CO2 into C2 products by Cd0.8Zn0.2S/In2O3 photocatalyst with a special nanostructure. Without the addition of any sacrificial agent, the C2 yield of the catalyst reached 0.382 μmol h−1, which is one of the highest performances to date. In situ experimental and computational studies show that CO2+ activated by NTP has higher π orbital and HUMO levels of lone pair electrons and promotes the reduction of CO2+ by injecting electrons into the vacant orbital of the active site of Zn. At the same time, the unique structure of Cd0.8Zn0.2S/In2O3 photocatalyst can extend the life of charge through the optical field enhancement effect, and then react with the CO2+ intermediates generated by NTP technology to promote the coupling of C-C bonds, and finally promote the photocatalytic multi-electron reaction to produce C2 hydrocarbons.

Porphyrin Supramolecular Nanoassembly/C3N4 Nanosheet S-Scheme Heterojunctions for Selective Photocatalytic CO2 Reduction toward CO.

The photocatalytic reduction of CO2 with H2O into valuable chemicals is a sustainable carbon-neutral technology for renewable energy; however, the photocatalytic activity and product selectivity remain challenging. Herein, an S-scheme heterojunction photocatalyst with superior CO2 photoreduction performance─porous C3N4 (CN) nanosheets anchored with zinc(II) tetra(4-cyanophenyl)porphyrin (ZnTP) nanoassemblies (denoted as ZnTP/CN)─was designed and prepared via a simple self-assembly process. The constructed ZnTP/CN heterojunction had rich accessible active sites, improved CO2 absorption capacity, and high charge carrier separation efficiency caused by the S-scheme heterojunction. As a result, the obtained ZnTP/CN catalyst exhibited considerable activity for photocatalytic CO2 reduction, yielding CO with a generation rate of 19.4 μmol g-1·h-1 and a high selectivity of 95.8%, which is much higher than that of pristine CN nanosheets (4.53 μmol g-1·h-1, 57.4%). In addition, theoretical calculations and in situ Fourier transform infrared spectra demonstrated that the Zn sites in the porphyrin unit favor CO2 activation and *COOH formation as well as CO desorption, thereby affording a high CO selectivity. This work provides insight into the design and fabrication of efficient S-scheme heterostructure photocatalysts for solar energy storage.

Synergistic CH4 hydrate recovery and CO2 storage by coupling depressurization with CO2/N2 injection: A pilot-scale investigation

To ensure sustainable energy supply while mitigating climate change, combining CH4 recovery with CO2 storage in marine natural gas hydrate (NGH) reservoirs is a promising carbon–neutral technology. In this study, a pilot-scale reactor (V = 22 L) was used to study the combined processes of CH4 recovery from the methane hydrate-bearing sediment by using depressurization followed by in-situ CO2/N2 injection to form mixed CH4/CO2/N2 hydrate (Mix-H) at marine NGH reservoir conditions (T = 283.8 K and P = 11.0 MPa). The bottom hole pressure (BHP = 3.2 MPa, 5.3 MPa, and 6.8 MPa) during depressurization and the setting of horizontal wellbore (HW), were systematically investigated to optimize the synergistic CH4 recovery and CO2 storage. The CH4 recovery ratio (55.4–80.6%) and the CH4 production rate (5.15–134.98 mol/d) increased as BHP decreased. After CO2/N2 injection, Mix-H formed first in the CH4-rich region in the upper section of the reactor and propagated downward to the lower. The Mix-H formation kinetics were significantly enhanced with an increase in BHP, leading to a decrease in CO2 composition in the Mix-H. The use of a horizontal wellbore (HW) facilitates a more even distribution of the CO2/N2 within sediments, resulting in a 13.5% increase in CO2 composition of Mix-H compared with no HW setting. The CO2 conversion ratio and hydrate restoration ratio reaches 52.8% and 69.4% at BHP = 5.3 MPa with HW, respectively. The technical feasibility of CO2 storage in exploited marine NGH reservoirs was first proved at pilot-scale. The results provided insights into the synergistic method of NGH exploitation and CO2 storage at the marine NGH reservoirs.

Grid interconnections and decarbonization pathways for carbon neutrality of Northeast Asia

As the three major greenhouse gas emitters in Northeast Asia (NEA), China, South Korea, and Japan, have joined the global carbon neutrality movement, this study examines interstate power transmissions between the countries to be considered for optimal technology pathways towards the net zero emission target. Using a bottom-up least-cost energy system model, intertemporal investment decisions are made between 2015 and 2065 in 10-year time steps subject to short-term/long-term emission targets in a range of carbon prices (0,100,200,300 USD/tCO2). Results show that under the carbon neutrality target, interstate power trade enables earlier carbon phaseout at a lower cost by increasing renewables utilizations and reduces investment burdens for high-cost carbon-neutral technologies like hydrogen. We find grid interconnections increase renewable penetrations at all nodes, while carbon pricing above 200 USD/tCO2 is required to ensure all participating nodes benefit from earlier carbon reduction. Ambitious carbon pricing is also important for closing gaps in emission impacts of short-term and long-term emission targets, calling for urgent actions to remove market distortion in power sectors. Lastly, sensitivity analysis to trade limits and nuclear utilization shows trade makes a greater contribution to carbon phaseout with relaxed trade terms and nuclear deployment.

Experimental characterization of ammonia, methane, and gasoline fuel mixtures in small scale spark ignited engines

In this study, gaseous anhydrous ammonia is blended with fuels like gasoline and methane and tested in an instrumented, low-technology single cylinder carbureted engine. In-cylinder pressure and emissions are monitored with the various mixtures and their performance is then compared with pure gasoline. With the addition of ammonia, the stability of combustion inside the combustion chamber was affected. But with the addition of a combustion modifier, the overall variability was reduced. At higher substitutions of ammonia, Initial results show an increase in indicated thermal efficiency of the engine. There is also a substantial decrease in the heat release rate (HRR) of the engine when substituting gasoline with ammonia. With the addition of methane, the change in the fuel reactivity helped improve HRR. Increasing ammonia substitution also resulted in an increase in indicated efficiency when compared to pure gasoline by approximately 12% with 50% substitution of ammonia in gasoline. Adding ammonia to the fuel mixtures also showed an initial reduction in unburnt hydrocarbon emission, followed by a sudden increase with further increasing concentration, suggesting incomplete combustion of the fuel mixture. The addition of methane with gasoline also showed a reduction in overall NOx emissions. Furthermore, methane was also tested as the main fuel with ammonia substitution of up to 50%. This ammonia and methane blend also showed comparable results to the gasoline, ammonia, and methane blends tested. From the emissions data, the catalyzing effects of ammonia were also seen with some cases showing varying trends with increasing ammonia substitution. Results from this study can be used to design small-scale engine based power generation systems that need very little modifications to accept ammonia based mixed fuels. Furthermore, this study lays the groundwork for using fuels blends with methane sourced using carbon neutral technologies and ammonia to power engine based systems.

Analysis of Carbon Storage Potential of CO2 Foamed Concrete

The technology of carbon capture, utilization, and storage (CCUS) is an important component of carbon neutral technology systems. To confirm the carbon storage potential of CO2 foamed concrete (CFC), this study addressed the principle of carbon storage in CFC materials. It is apparent that carbon storage of CFC materials includes carbon fixation in concrete skeletons and carbon storage in CFC bubbles. The carbon fixation of CFC skeletons is realized by CO2 mineralization. As the concrete skeleton in CFC is in the CO2 atmosphere, the carbonation of CFC materials or CO2 mineralization is more complete. Research shows that the carbonation rate of CFC materials can reach almost 30% after acidification, foaming with high CO2 pressure and curing in the atmosphere. The carbonation rate is higher than the rate in concrete curing with CO2. A mathematical model was established to calculate carbon fixation capacity in CFC materials, and the carbon fixation and storage capacity in CFC material were estimated. The results showed that more than 99% carbon storage of CFC was realized by the chemical carbonization of the concrete skeleton. Comparatively, the potential of carbon storage in the bubble of CFC was small. In this study, carbon storage capacity was divided into three categories, i.e., theoretical maximum capacity, relative reliable capacity, and expected capacity or potential. The carbonation rate for theoretical maximum capacity was 100%, when all the concrete was considered to be carbonated. As the carbonation rate of concrete during the whole life cycle is approximately 55% all over the world, 50% was set as the carbonation rate for relative reliable capacity calculation. If at high temperatures, CO2 curing with high pressure or accessory ingredients applied to silicate concrete can improve carbonation rate to be over 80%, when the carbon storage capacity is considered to be expected capacity or potential. In 2017-2021, the theoretical maximum capacity of carbon storage was 3.623×109 t CO2 in China, with 7.25×108 t·a-1. The relative reliable capacity was 3.75×108 t·a-1, and the expected capacity was 5.80×108 t·a-1. If the carbonation rate was 30%, the carbon storage of concrete produced annually in China during the whole life cycle reached 2.18×108 t, which was more than the carbon sink of Daxing'anling forest for one year. In coal electricity integrated mining areas and large thermal, metallurgical, cement chemical, and other high-energy consuming enterprises, CFC has a good prospect of development to promote the recycling of solid waste and waste gas. Meanwhile, it is pointed out that the stability of CFC before solidification is a technical problem to be solved in the next step.