Direct CO2 Emissions Research Articles

Exploring the potential of a novel passenger transport model to study the decarbonization of the transport sector

To explore sustainability strategies in the transport sector in a holistic way, a model dedicated to passenger transportation has been created as a part of the multiregional WILIAM model (Within Limits Integrated Assessment Model). Based on system dynamics, our model increases the diversity of existing passenger transport models within Integrated Assessments Models by offering a detailed representation of the dynamics of the transition for different technologies and transport modes combining technological and behavioural changes. It calculates the energy demand, direct emissions and additional material requirements of the transport sector and can be linked to other submodules of WILIAM to study different feedback loops. Here we report the validation of the offline model and illustrate its usefulness and practical applicability. First, a Baseline transport scenario for Spain was developed and parametrized. This scenario describes the plausible evolution of the Spanish passenger transport system in the absence of ambitious environmental policies but nevertheless achieves a reduction of total direct CO2 emissions from passenger transport from 66 Mt CO2/year in 2022 to 60 Mt CO2/year in 2035, after which emissions remain constant until 2050. Subsequently, following the Avoid-Shift-Improve approach, various behavioural change measures and technological improvements were introduced. The comparison of the different modelled measures reveals that the most effective tested strategy to reduce direct emissions is the transition to battery electric power trains for cars, buses, and motorcycles, however at the cost of the highest material requirements. Further work will be dedicated to the study of the implications of the link of this submodule with the rest of WILIAM.

Integration of physical information and reaction mechanism data for surrogate prediction model and multi-objective optimization of glycolic acid production

With the continuous development of the chemical industry, the concept of advocating green development has become increasingly popular. Glycolic acid (GA), serving as the monomer for biodegradable plastic polyglycolic acid, plays a crucial role in combating plastic pollution and fostering an eco-friendly society. The selective oxidation of ethylene glycol (EG) to produce GA represents a novel green production technology. Controlling reaction parameters to achieve multi-objective optimization of product distribution and direct CO2 emissions is crucial for scaling up the process. With the advent of the big data era, the integration of the chemical industry with artificial intelligence to achieve engineering scale-up is an important trend. This study proposes a neural network model for production prediction and optimization. The model is trained using experimental data, reaction mechanism data, and physical information, enabling rapid prediction of GA production. After validating with 40% of experimental data and 16% of reaction mechanism data, the model's prediction error was within ±5%, and the linear correlation coefficient R2 between the predicted values and actual values was 0.998. Furthermore, this study integrated a multi-objective optimization algorithm based on the model, enabling surrogate optimization of reaction parameters during production. After optimization, the direct CO2 emissions were reduced by over 99% and overall greenhouse gas emissions were reduced by 4.6%. The research paradigm proposed in this research can offer guidance and technical support for the optimized operation of EG selective oxidation to GA.

Intensification of the CO2-capturing methanol steam reforming process: A comprehensive analysis of energy, economic and environmental impacts

The methanol (MeOH) steam reforming (MSR) process plays an important role in the MeOH-based international renewable energy supply chain. To address the challenges related to the high cost and substantial CO2 emissions linked to the state-of-the-art integrated MSR process, this study aims to propose and enhance an intensified MSR process focusing on energy utilization, economic viability and environmental impact. Aside from the MSR process, the overall scenario also includes the water–gas-shift reaction (WGS) process, CO2 capture using amine-based methods, liquefaction, and hydrogen purification through pressure-swing adsorption. Based on this study, apparent enhancements of the state-of-the-art MSR process can be achieved by adjusting key process variables, especially those related to the CO2 capture process, and by incorporating various intensification strategies, including heat integration (with feed-effluent heat exchangers) between the MSR and the WGS processes, implementing a side-draw intercooling structure of the CO2 absorber, splitting the rich solvent flow to the CO2 stripper, and employing a multi-stage CO2 stripper with vapor recompression. Compared to the state-of-the-art MSR process in the literature, the intensified MSR process produces ultra-pure hydrogen (99.99 mol%) as a main product while reduces 6.2 % of the shared cost (from 191.0 USD/t-MeOH to 179.1 USD/t-MeOH), increases the overall carbon capture rate by 3 % (from 86.73 % to 89.99 %), and reduces the direct CO2 emission by approximately 25 % (from 1.41 t-CO2/ t-MeOH to 1.06 t-CO2/ t-MeOH). Within a MeOH-based international renewable energy supply chain, these enhancements can also significantly lower the imported cost of electricity from 105.9 USD/MWh to 95.5 USD/MWh.

Reduction of greenhouse gases emissions by use of hydrogen produced in a refinery by water electrolysis

The study considers production of hydrogen in a local oil refinery by electrolysis of water using exclusively electricity from renewable energy sources. Produced hydrogen is to be used as fuel for cars and buses. However, in case when the demand for hydrogen is less than production, which is expected in the beginning, as currently there are no hydrogen vehicles in Croatia, excess of produced green hydrogen would be used in the refinery production process, partially substituting hydrogen currently being produced from natural gas. The carbon footprint of hydrogen currently being produced in the refinery is calculated taking into account direct and indirect (upstream) CO2 emissions as well as methane fugitive emissions, along with the NOx emissions, converted to the amount of equivalent CO2 emissions. Each kg of green hydrogen used to power city buses instead of diesel would reduce well-to-wheels CO2 emissions by 33.39 kg, and when used to power cars instead of gasoline it would reduce them by 28.99 kg. If green hydrogen is used as a replacement for gray hydrogen produced from natural gas in the refinery, it would reduce the CO2 emissions by 21.74 kg per each kg of hydrogen substituted.

The nexus between direct air capture technology and CO2 emissions in the transport sector

Deploying negative emission technologies has become crucial for limiting the global temperature rise to approximately 1.5 °C above preindustrial levels. DAC technologies are being explored as one of the prospective options. These technologies have been thoroughly investigated as a potential project to capture CO2 emissions and provide purified air, natural gas, or fuel oil. An applied approach, on the other hand, was not taken into consideration while evaluating the influence that this technology has on emissions. For this reason, British Columbia provides a substantial chance to examine emissions that were produced after the DAC actions were put into place in 2015. In this study, the difference-in-differences methodology is employed for the very first time to compare the emissions that are produced by the transport sectors in British Columbia with those emitted by other provinces in Canada. The role that GDP and population play in the release of emissions is also taken into consideration in this paper. Based on the research results, it can be observed that the implementation of DAC initiatives has yielded notable effects. Evidence shows that the DAC effort has led to an average reduction of 0.08 in logarithmic CO2 emissions in the transport sector. By accounting for GDP and population, the empirical results indicate that DAC technology reduced CO2 emissions in British Columbia compared to provinces without DAC facilities. DAC initiatives are expected to become increasingly prevalent between the mid-2030s and 2040s. Overall policy implications suggest that there is a need for DAC technologies to collaborate with alternative mitigation technologies, or alternative technologies should collaborate with DAC technologies that are more efficient to achieve the targeted goals in a short time.

Does industrialization promote the emission mitigation agenda of East Africa? a pathway toward environmental sustainability

Africa’s economy continues to be characterized by increasing environmental pollution caused by anthropogenic activities. Despite the implications of environmental pollution in the continent, little attention has been paid to it, although almost all its countries are signatories to the Paris Agreement. One macroeconomic variable that has proven to be a major driver of environmental pollution in the region is industrialization. However, despite the numerous explorations on the connection between industrialization and environmental degradation, limited studies have examined the linkage amidst the series in East Africa. This study was, therefore, conducted to help fill that gap. In accomplishing this goal, econometric techniques that control cross-sectional correlations, heterogeneity, and endogeneity, among others, were employed for the analysis. From the results, the panel under consideration was heterogeneous and cross sectionally correlated. In addition, the studied series were first differenced stationary and co-integrated in the long run. The elasticities of the regressors were explored via the cross sectionally augmented autoregressive distributed lag (CS-ARDL) estimator, the cross sectionally augmented distributed lag (CS-DL) estimator, and the augmented mean group (AMG) estimator. According to the results, industrialization led to a reduction in the environmental quality in the region through high CO2 emissions. In addition, financial development, foreign direct investments, urbanization, and energy consumption were not environmentally friendly in the bloc. On the causal linkages amid the series, bidirectional causalities between industrialization and CO2 emissions, energy consumption and CO2 emissions, and foreign direct investments and CO2 emissions were detected. Finally, one-way causal movements from financial development and urbanization to CO2 emissions were unraveled. These findings are useful in helping stimulate the emission mitigation agenda of the region. Based on the findings, the study recommended, among others, that national policies that can promote energy conservation at the industrial level and can convert the industrial structure of the region to a low carbon-intensive one should be formulated.

Pressurized Chemical Looping for Direct Reduced Iron Production: Economics of Carbon Neutral Process Configurations

The replacement of the blast furnace—basic oxygen furnace (BF-BOF) steelmaking route with the direct reduced iron—electric arc furnace (DRI-EAF) route reduces the direct CO2 emissions from steelmaking by up to 68%; however, the DRI shaft furnace is one of the largest remaining point source emitters in steelmaking. The capital and operating expenses of two potential nearly carbon-neutral DRI process configurations were investigated as a modification to a standard Midrex DRI facility. First, amine-based post-combustion capture with a 95% capture rate was considered as the benchmark, as it is currently commercially available. A second, novel configuration integrated the Midrex process with pressurized chemical looping—direct reduced iron (PCL-DRI) production. The capital expenditures were 71% and 28% higher than the standard Midrex process for a Midrex + amine capture plant, and a PCL-DRI plant, respectively. There was an incremental variable operating cost of USD 103 and USD 44 per tonne of CO2 for DRI production using amine capture and PCL-DRI, respectively. The amine capture configuration is most sensitive to the cost of steam generation, while PCL-DRI is more sensitive to the cost of electricity and the makeup oxygen carrier. An iron-based natural ore is recommended for PCL-DRI due to the low cost and availability. Based on the lower costs compared to amine-based post-combustion capture, PCL-DRI is an attractive means of eliminating CO2 emissions from DRI production.

Mineralisation of CO2 in wood biomass ash for cement substitution in construction products

This study extends our exploration of the potential of biomass ashes for their CO2-reactivity and self-cementing properties. The ability of three hardwood-based biomass ashes to mineralise CO2 gas and partially replace CEM I in mortars was investigated. The three hardwoods were English oak (Quercus rober), English lime (Tilia x europaea), and beech (Fagus sylvatica). The woody biomass wastes were incinerated at 800°C to extract their key mineral phases, which are known to be reactive to CO2 gas to form carbonates. The selected biomass ashes were analysed for their CO2-reactivity, which was in the range of 32–43% (w/w). The ashes were used to replace CEM I at 7 and 15% w/w and this “binder” was mixed with sand and water to produce cylindrical monolithic samples. These monoliths were then carbonated and sealed cured over 28 days. The compressive strength, density and microstructure of the carbonate-hardened monoliths were examined. The ash-containing monoliths displayed mature strengths comparable to the cement-only reference samples. The CO2 uptake of oak containing monoliths was 7.37 and 8.29% w/w, for 7 and 15% ash substitutions, respectively. For beech and English lime they were 4.96 and 6.22% w/w and 6.43 and 7.15% w/w, respectively. The 28 day unconfined compressive strengths for the oak and beech ashes were within the range of ~80–94% of the control, whereas lime ash was 107% of the latter. A microstructural examination showed carbonate cemented sand grains together highlighting that biomass ash-derived minerals can be very CO2 reactive and have potential to be used as a binder to produce carbonated construction materials. The use of biomass to energy ash-derived minerals as a cement replacement may have significant potential benefits, including direct and indirect CO2 emission savings in addition to the avoidance of landfilling of these combustion residues.

Development of Mass–Energy Balance Model Based on a New Process of RSF with Hy-O-CR

At present, blast furnace (BF) ironmaking is still the main process for producing hot metal in China and around the world. Under the constraint of the global goal of “double carbon”, it is urgent to carry out hydrogen metallurgical innovation for the existing BF ironmaking process with higher carbon emissions. In recent years, BF technology with hydrogen enrichment and pure oxygen has made some progress, effectively reducing carbon emissions of hot metal per tons, but it is still unable to break through the technical bottleneck of emission reduction of more than 30%. In view of this, the authors put forward an ironmaking technology of a reduction smelting furnace (RSF) that is hydrogen-rich and utilizes pure oxygen and carbon recycle (Hy-O-CR), which breaks through the technical defect of traditional BF emission reduction of less than 30% by reshaping the furnace. Firstly, the construction process of the mass and energy balance model for two main unit modules in the new process (RSF with Hy-O-CR and top gas cycle) is introduced, and then the parameter optimization under specific scenario conditions is analyzed, and the influence mechanism of several key variables on the parameters in the furnace is obtained. Finally, the emission of CO2 in the whole process is explored in the case of two typical operating parameters. The results show that after using CCUS technology, the minimum value of direct CO2 emission is 215.93 kg/tHM, which is as high as 84.58% compared with the traditional BF process. Even if the removed CO2 is counted in carbon emissions, the minimum value of direct or indirect carbon emissions is 729.85 kg/tHM, and the proportion of emission reduction can reach 47.87%. The research results show that the reconstruction of Hy-O-CR technology can change the ratio of direct reduction and indirect reduction, which greatly breaks through the emission limit of the traditional BF and provides a new reference for hydrogen metallurgy technology and a basis for further study of the optimization of RSF size.

Sustainable iron production via highly efficient low-temperature electrolysis of 3D conductive colloidal electrodes

Low temperature electrolysis at 100 °C with 3D-conductive Fe2O3 colloidal electrodes is used to produce high purity Fe powder and other metal powders with no direct CO2 emission.

Energetic advantages and well-being improvement for building occupants, connected to dynamic building envelope solutions, with special focus on intelligent solar shading and ventilative cooling of NZEB and ZEB buildings

Across Europe, rising outdoor air ambient temperatures connected to the global warming and climate change, combined with an ageing population and urbanisation, are putting in evidence that population is potentially becoming more vulnerable to heat in summer especially during heatwaves. In particular high energy efficient buildings designed without consideration for potential “overheating” mitigation are foreseen in the future to be at risk of summertime discomfort and rising costs (and relative direct or indirect CO2 emissions) for additional air conditioning operation needs. Beside the best HVAC technologies, intelligent solar shading and ventilative cooling are considered, by several EU governments and experts, two key elements for further improving the energy efficiency of existing buildings and optimising the low-energy designs of new buildings. These technologies seems still under-utilised despite the fact it provides a major impact on the reduction of energy consumption of the built environment and, for this reason, present paper is concentred on the evaluation of the advantages represented by the use of intelligent solar shading and ventilative cooling in order to take the best energetic impact form solar heat gains in winter and minimise these heat gains in summer, also using the air ambient cooling energy hence reducing the cooling loads to be solved with mechanical cooling at total benefit of even more energy efficient and resilient / future-proof buildings.

Methodological approaches to the CO2 emissions estimation in rail transport

Today there is a growing interest in the problems of assessing the impact of greenhouse gases on the environment. Modern methods for estimating the volume of CO2 emissions from cargo transportation processes are inaccurate. The study aims to develop a methodology for calculating and estimating the volume of CO2 emissions generated by rail transport during the transportation of goods and its subsequent validation. Research methods – analysis of Russian and international regulatory documents, scientific and practical methodological approaches to determine the volume of CO2 emissions for rail transport. It is substantiated that the actual methodological approach should consider direct emissions, indirect emissions and specific parameters: carbon intensity and cargo intensity, mass of transported cargo. The result of study is a methodology for calculating the volume of CO2 emissions, considering the specifics of freight transportation on railway transport and accounting for direct and indirect CO2 emissions. An example of calculating the volume of CO2 emissions during the transportation of building materials by rail between St. Petersburg and Murmansk is given. The proposed methodology makes it possible to include the amount of estimated CO2 emissions in the service, which will facilitate the introduction of "green" certificates for customers.

Numerical investigation of radiative transfer during oxyfuel combustion of hydrogen and hydrogen enriched natural gas in the container glass industry

The substitution of natural gas with hydrogen is one way to eliminate direct CO2 emissions. However, oxyfuel combustion of hydrogen or hydrogen enriched natural gas leads to different exhaust gas properties due to a changed composition compared to conventional combustion. In combustion simulation, the emissivity of a gas mixture is usually approximated using a Weighted Sum of Gray Gases (WSGG) model. Most of the existing WSGG models have been validated for natural gas combustion with air or oxyfuel and are therefore not applicable to hydrogen-oxyfuel combustion. CFD simulations showed, that none of the investigated WSGG models is able to predict the radiative heat transfer for all considered combustion scenarios with appropriate accuracy. In addition, in container glass manufacturing more than 95% of the heat flux to the glass surface is transferred by radiation because of the high process temperatures. Due to the changed gray gas emissivity, the high content of water vapor leads to a different emission spectrum of the exhaust gas. The influence of the changed emission spectrum on radiative heat transfer and the penetration depth of radiation in the glass melt is investigated using a simulation model of a pilot plant and non-gray modelling of the radiation transport. The CFD simulations show slightly enhanced radiative heat transfer to the glass and a slightly deeper penetration depth especially for wavelength below 2.2 μm for hydrogen-oxyfuel combustion.

Exploring the optimal threshold of FDI inflows for carbon-neutral growth in Africa.

This study investigates the relationship between foreign direct investment (FDI) and CO2 emissions in Africa, primarily emphasizing carbon-neutral growth. Employing advanced econometric methods like the Generalized Method of Moments (GMM), fixed effect, and Two-Stage Least Squares (2SLS), we identify critical threshold values for key variables, including economic growth, trade openness, human capital, financial development, inflation, and population growth. Our findings indicate that GDP significantly influences the FDI-CO2 emissions relationship as economies expand, shifting from negative to positive, potentially leading to increased carbon emissions. Higher trade-to-GDP ratios are associated with reduced CO2 emissions due to cleaner technologies and greener production practices. Additionally, financial development plays a pivotal role, enabling investment in sustainable technologies. Nations with a more skilled workforce are more likely to adopt sustainable practices. The influence of population growth on CO2 emissions is complex, balancing increased demand with investments in clean technologies. The study recommends that African policymakers prioritize FDI aligned with carbon-neutral growth by promoting sustainability, investing in human capital, and carefully balancing population growth with sustainability.

Carbon recovery from biogas through upgrading and methanation: A techno-economic and environmental assessment

Reducing the use of fossil fuels is an essential measure to counteract the rise in greenhouse gas emissions. In this context, biofuels and e-fuels make an important contribution to achieving climate neutrality targets, especially if their distribution can take place within existing infrastructure, as in the case of methane.The aim of this work is to carry out a techno-economic and environmental assessment of the combined production of biological and synthetic methane in a wastewater treatment plant (WWTP). Methane yield from biogas, usually associated only with biogas upgrading, is enhanced by recovering CO2 to produce additional synthetic natural gas (SNG) through a methanation process. The analysis is applied to a medium-sized WWTP in Italy, whose biogas production profile is known throughout the year.In the current scenario, SNG is not competitive on the gas market. The investment costs of the technologies and the electricity price are then varied in order to better investigate the profitability of SNG production. The results show that, considering long-term cost projections and an electricity price of about 50 €/MWh, SNG can become competitive, with a production cost of 1.4 €/Sm3. Finally, the environmental competitiveness of SNG (direct and indirect CO2 emissions) with respect to fossil natural gas is investigated: results are shown as a function of the carbon intensity of grid electricity and the share of local renewable energy. To make SNG environmentally sustainable, the renewable share must increase to 46% or, alternatively, the carbon intensity of grid electricity must decrease to 187 gCO2eq/kWh.

Life cycle assessment of photovoltaic module backsheets

AbstractIncreased deployment of solar photovoltaic (PV) enables the transition to decarbonized energy systems, capable of tempering the dire consequences of global warming. Even though backsheets are very important regarding lifetime energy yield of the PV module, the environmental impacts of their production, use, and end‐of‐life (EoL) processing are largely neglected. As part of a recently finalized Dutch national project EXTENSIBLE (Energy yield assessment of neXT gENeration and SustaInaBLE backsheets), the environmental impacts for 7 different polymeric backsheets have been evaluated via a life cycle assessment (LCA). The selected backsheets include 3 traditional polyethylene terephthalate (PET)‐based backsheets with a fluorine containing outer layer (two white pigmented and one fully transparent). The other 4 backsheets are novel high‐performance polyolefin (PO)‐based backsheets, manufactured by Endurans Solar™, also including one transparent version. From results of the LCA, it is concluded that in comparison with PET‐based backsheets and fluoropolymer containing backsheets, PO‐based backsheets perform best in terms of energy yield, reliability, and environmental impacts. The production of fluoropolymer‐ and PET‐based backsheets cause substantial environmental impacts, especially regarding climate change and ozone depletion. This conclusion is corroborated by recent literature data. Regarding the EoL phase, it was shown from a theoretical assessment that pyrolysis of the spent backsheets potentially leads to much lower global warming potential (GWP) when compared to incineration, especially for the PO‐based backsheets. Incineration of the shredded and solid backsheet material causes direct emissions of CO2 with a limited heat recovery potential only. Deploying pyrolysis for spent PO‐based backsheets significantly improves their life‐time GWP per kWh produced. Pyrolysis offers the possibility to recover a large part of the PO as an usable pyrolysis oil that might serve as feedstock for chemicals or as transportable liquid fuel for the generation of process heat in recovery boilers, thereby avoiding the use of new fossil resources. EoL pyrolysis (or incineration) of fluoropolymer‐based backsheets is problematic due to the presence of fluorinated hydrocarbons, leading to corrosive and/or toxic products.

A Study on the Potential of Carbon Dioxide Utilization Through its Co‐Injection with Hydrogen into the Blast Furnace Tuyeres

The potential of CO2 utilization through its injection into blast furnace (BF) tuyeres is studied using the 1D steady‐state zonal model. Scenarios with the injection of CO2, hydrogen, and their co‐injection at various H2/CO2 mass ratios are analyzed. The impacts on factors affecting vertical temperature patterns and the position of the cohesive zone in the BF are identified. A life cycle assessment for several scenarios with various carbon emissions intensities of hydrogen production, carbon capture, and grid electricity generation is performed. Injection of CO2 without the addition of hydrogen increases the coke rate, reduces productivity, and increases direct CO2 emissions; however, thanks to producing top gas with higher calorific value, injection of CO2 may reduce the global warming potential (GWP) if the electric grid carbon intensity is above 654 kg‐CO2 kWh−1, while carbon capture is powered by green electricity. Although the injection of hydrogen alone would result in a more substantial reduction of GWP from the baseline than the injection of H2/CO2 mix at any mass ratio, considering the identified impacts on heat exchange and the position of the cohesive zone in the BF, co‐injection might be an enabling solution for the adoption of hydrogen injection.

Renovated or replaced? Finding the optimal solution for an existing building considering cumulative CO2 emissions, energy consumption and costs – A case study

The buildings sector is responsible for 37 % of global final energy consumption and nearly 40 % of total direct and indirect CO2 emissions. This has led to promoting renovation efforts to decrease operational emissions of the existing building stock. With decreasing operational emissions, embodied emissions are becoming more important. In new buildings, embodied emissions account for about half of total emissions through the life cycle of a building. If both embodied and operational emissions are considered, renovation often outperforms new constructions, due to high embodied emissions of the structure - especially solid construction with a basement. Based on this, the decision if a building should be renovated or replaced is often not straight forward and depends on various factors. In this paper, a typical German building was considered as a case study, for which both renovation and replacement scenarios were considered, to identify the optimal solutions in terms of overall energy consumption and CO2 emissions of the building in the use phase, the environmental impacts of the building along its entire life cycle, and related costs. Results show that the lowest CO2 emissions during the lifetime of the analyzed building can be achieved with a sustainable replacement building (-2.05 kg CO2/m2/year) by using a heat pump with ground collector coupled with PV. This allows, compared to the existing reference building, reductions of 97 % and 101 % in terms of energy consumption and CO2 emissions, respectively; while natural gas-based technologies are the least targeted and the most volatile to fuels’ prices changes over the years.

Significant thermal upgrade via cascade high temperature heat pump with low GWP working fluids

High temperature heat pump is a promising solution for efficient high temperature heat supply. However, the poor performance when it operates in large temperature lift hinders it from utilizing low temperature waste heat. To solve this problem, a cascade high temperature heat pump with economized vapor injection was established and a simulation model was developed accordingly. The tests were conducted using R134a/R245fa and R1234ze(E)/HP-1 at heat source temperature from 5 to 30 °C and heat sink temperature from 90 to 120 °C, with the coefficient of performance (COP) varying in the range of 1.72–2.73 and 1.77–2.75, respectively. The COP about 2.20 was achieved with R1234ze(E)/HP-1 at optimal intermediate temperature and optimal economized vapor injection pressure when the temperature lift is 100 °C. In the simulated case study, the heat pump water boiler based on the experimental prototype decreases CO2 emission by 62.8 % compared to electric boiler. Moreover, using low GWP working fluids reduces 1.32 × 104 kg direct CO2 emission in TEWI. Under the current technological, pricing, and operational condition, it takes 16 years for heat pump to have economic benefit over electric boiler, but this duration can be shortened with reduced initial cost, improved COP, and increased operating hours and electricity price. In summary, this work presented a high-efficient, environmentally friendly, and economically viable cascade high temperature heat pump system which has potential to utilize the abundant environmental heat source and deliver high temperature heat, being an alternative to the conventional heat generation equipment such as boilers.

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.