Process Energy Requirements Research Articles

Accuracy of enteric methane emission models for cattle in sub-Saharan Africa: status quo and the way forward.

Cattle emit over 65% of enteric methane (CH4) in sub-Saharan Africa (SSA), making them the focus of many mitigation strategies targeting livestock emissions. Since measured feed intake data are sparse, emission factors for enteric CH4 (EFCH4) are mainly estimated indirectly from gross energy intake (GEI) using the net energy (NE) requirements for different metabolic processes in cattle. However, all NE requirement systems commonly used for cattle in SSA were developed for cattle in temperate regions. Therefore, we assessed the suitability of different enteric CH4 models for estimating the GEI of cattle in SSA. The Intergovernmental Panel on Climate Change (IPCC) and South African models were identified as the main tier 2-based methods used to estimate enteric CH4 emissions from cattle in SSA. In the IPCC model, EFCH4 was estimated as (GEI * [Ym/100])/55.65, where Ym is the conversion factor (%) of gross energy in feed to CH4 and 55.65 the energy content of CH4 (MJ/kg). The GEI was estimated based on NE requirements for different metabolic processes in cattle as per the American National Research Council. In the South African model, EFCH4 was estimated as (Y/100 * GEI/55.22), where Y is the CH4 yield and 55.22 is the energy content of CH4; Y was calculated from the dry matter (DM) digestibility while GEI was calculated by predicting DM intake and multiplying it by 18.4 MJ (gross energy per kilogram DM). Also, the suitability of the British and German NE requirement systems was assessed as alternatives used for cattle nutrition in SSA. These NE systems were implemented in the IPCC model to yield the "AFRC" and "GfE" models, respectively. The four models were then evaluated using an evaluation dataset summarizing feed quality and DM intake results from 21 studies conducted in SSA, with 125 dietary treatments, and 822 cattle observations. The relative prediction error (RPE) and concordance correlation coefficient (CCC) were used to evaluate the models' accuracy. Only the South African model estimated the GEI in dairy cattle with an acceptable RPE (18.9%) and highest CCC (0.87), while the other three models yielded estimates with RPE > 20%. None of the four models we assessed estimated GEI for other cattle (i.e., nondairy) with an RPE < 20% or CCC > 0.30. The inaccuracy in GEI estimates suggests an error of the same magnitude in EFCH4 estimates. Therefore, a concerted effort is needed to improve the accuracy of enteric CH4 estimation models for cattle in SSA.

Raspberry pulp pasteurization: Computational fluid dynamics modeling and experimental validation of color and bioactive compound retention

AbstractThis work evaluated the heat transfer, fluid flow, and different reactions that occur during the pasteurization of raspberry pulp. The pulp was packed in glass jars and thermal processing was conducted by immersion in a water bath. The process was evaluated by multiphysics modeling, with the aim of determining the temperature distribution, flow pattern, the slowest heating zone (SHZ) location, the microbial inactivation, and the quality changes taking place during processing. In order to simulate the process accurately, a model was developed using experimentally measured product and heat transfer properties (density, thermal expansion, specific heat, thermal conductivity, apparent viscosity, and convective heat transfer coefficient) and kinetics of thermal degradation of quality parameters (color, anthocyanin, and ascorbic acid). The model was successfully validated against experimental measurements of both temperature and quality losses. After validation, the model was used to design and evaluate equivalent thermal processing conditions. Improved processes were identified that minimized the changes of color and the bioactive compounds, while maintaining product safety and stability.Practical ApplicationsThermal processing of raspberries may induce several physicochemical changes that impair their sensorial properties, and may reduce the content of nutrients and bioactive compounds. Hence, the design and optimization of heat treatments is a key tool to guarantee safety while, at the same time, minimizing detrimental side effects which involve a loss of quality. In this investigation, we assessed the actual thermo‐physical properties of raspberry pulp and the system heat transfer coefficients. Then, we developed a CFD model to predict the temperature and velocity transient profiles, the location of the SHZ, and the quality changes occurring in raspberry pulp during pasteurization. The findings of this study could be useful to food processors for optimizing pasteurization conditions in order to obtain safe and high‐quality raspberry pulp preserves, as well as for reducing processing energy requirements.

Neutron tomography of porous aluminum electrodes used in electrocoagulation of groundwater

In this work, neutron computed tomography (CT) is employed to investigate the dissolution of porous aluminum electrodes during electrocoagulation (EC). Porous electrodes were chosen in efforts to reduce electric power requirements by using larger surface-area electrodes, having both inner and outer surface, for the EC process. Neutron CT allowed 3D reconstruction of the porous electrodes, and image analysis provided the volume of each electrode vs. thickness, which can indicate whether the inner surface is effectively involved in EC reactions. For the anode, the volume decreased uniformly throughout the thickness of the electrode, indicating that both the outer and inner surface participated in electrochemical dissolution, while the volume of the cathode increased uniformly vs. thickness, indicating deposition of material on both the outer and inner surface. The attenuation coefficient vs. thickness, increased for both anode and cathode, indicating surface chemistry changes. For the anode, the attenuation coefficient increased slightly but uniformly, probably due to aluminum oxide formation on the surface of the anode. For the cathode, the attenuation coefficient increased more than for the anode and nonuniformly. The higher increase in the attenuation coefficient for the cathode is due to precipitation of aluminum hydroxide on the electrode surface, which added hydrogen. Image analysis also showed that, although the attenuation coefficient increased throughout the thickness of the electrode, most of the hydroxide deposition occurred on the outer surface. Energy analysis showed that porous electrodes can be used to reduce process energy requirements by as much as 4 times compared to solid electrodes.

Integrated early-stage environmental and economic assessment of emerging technologies and its applicability to the case of plasma gasification

Economic and environmental impact assessments are increasingly being adopted in the design and implementation of emerging systems. However, their emerging nature leads to several assessment challenges that need to be addressed to ensure the validity and usefulness of results in understanding their potential performance and supporting their development. There is the need to (i) account for spatial and temporal variability to allow a broader perspective at an early stage of development; (ii) handle uncertainties to systematically identify the critical factors and their interrelations that drive the results; (iii) integrate environmental and economic results to support sound decision-making based on two sustainability aspects. To address these assessment challenges, this study presents an alternative approach with the following corresponding features: (i) multiple scenario development to conduct an exploratory assessment of the systems under varying conditions and settings, (ii) global sensitivity analysis to identify the main critical factors and their interrelations, and (iii) trade-off and eco-efficiency analysis to integrate the economic and environmental results. The integrated approach is applied to a case study on plasma gasification for solid waste management. The results of the study highlight how the approach allows the identification of the dynamic relations between project settings and surrounding conditions. For example, the choice of gasifying agent largely depends on the background energy system, which dictates the impacts of the process energy requirement and the savings from the substituted energy of the syngas output. Based on these findings, the usefulness and validity of the proposed integrated approach are discussed in terms of how the key assessment challenges are addressed and how it can provide guidance for the development of emerging systems.

Evaluation of thermophysical data, COSMO‐SAC predictions, and feed simplifications for aromatic extraction process simulation using ionic liquid [EMIM][NTf2

AbstractIonic liquids (ILs) are promising alternatives to conventional solvents for selective separation of aromatics from hydrocarbon mixtures, and their implementations depend on economic feasibility demonstrated by process simulation. Prior process modeling studies typically assume simplified hydrocarbon feeds or use the COSMO‐SAC predictive model. Our goal is to evaluate how feed simplifications and COSMO‐SAC predictions impact process modeling. We collect experimental data for 1‐Ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf2]) from the ILThermo database to regress UNIQUAC model binary interaction parameters for 17 hydrocarbons. We find that feed simplifications tend to significantly underpredict process energy requirements and fail to reveal important details in the extractive distillation section of the process. COSMO‐SAC predictions underpredict activity coefficient of aliphatics in [EMIM][NTf2] by a large margin, which leads to lower aromatic‐aliphatic selectivities and overprediction of process energy requirements. It is significant enough to lead to the conclusion of process infeasibility in the case of [EMIM][NTf2].

Impact of polymer molecular weight on the efficiency of temperature swing solvent extraction for desalination of concentrated brines

Thermally-responsive non-ionic polymers can be used for temperature swing solvent extraction to desalinate concentrated brines. We determined how polypropylene glycols [PPG] with number average molecular weights (Mn) of 425, 725 or 1000 g/mol affected the quantity and quality of the extracted water, and overall process energy requirements using model 10 wt% NaCl (~100 g/L TDS) and field derived (82.1 g/L TDS) concentrated brines. The amount of water recovered and its salinity was highest for PPG425 (lowest Mn) and lowest for PPG1000 (highest Mn). PPG725 (intermediate Mn) provided the best balance between water recovery and salt rejection. PPG725 produced a water with low salinity (<1.6 wt% NaCl) from a field derived brine using a 20:1 Solvent:Feed ratio, with an overall energy consumption of 49 ± 13 kWh/m3treatedwater. This is comparable with mechanical vapor compression crystallizers (>50 kWh/m3treatedwater). The influent feed salinity at 20:1 S:F did not affect the water extraction efficiency, and NaCl(s) forms in the raffinate, suggesting the potential for near zero liquid discharge desalination in this process. Overall, PPG725 is a promising polymer for desalination of highly concentrated brines. Improving the efficiency of the water-polymer separation during thermal regeneration would further improve the attractiveness of this approach.

The Environmental Impacts of Carbon Capture Utilization and Storage on the Electricity Sector: A Life Cycle Assessment Comparison between Italy and Poland

Carbon Capture Utilization and Storage (CCUS) is a set of technologies aimed at capturing carbon dioxide (CO2) emissions from point-source emitters to either store permanently or use as a feedstock to produce chemicals and fuels. In this paper, the potential benefits of CCUS integration into the energy supply sector are evaluated from a Life Cycle Assessment (LCA) perspective by comparing two different routes for the CO2 captured from a natural gas combined cycle (NGCC). Both the complete storage of the captured CO2 and its partial utilization to produce dimethyl ether are investigated. Moreover, the assessment is performed considering the region-specific features of two of the largest CO2 emitters in Europe, namely Italy and Poland. Results shows that the complete storage of the captured CO2 reduces Global Warming Potential (GWP) by ~89% in Italy and ~97%, in Poland. On the other hand, the partial utilization of CO2 to produce dimethyl ether leads to a decrease of ~58% in Italy and ~68% in Poland with respect to a comparable reference entailing conventional dimethyl ether production. A series of environmental trade-offs was determined, with all the investigated categories apart from GWP showing an increase, mainly connected with the higher energy requirements of CCUS processes. These outcomes highlight the need for a holistic-oriented approach in the design of novel implemented configurations to avoid burden shifts throughout the value chain.

Characterization of a New Fiber from Cyperus Dichrostachus A.Rich Plant

Natural fibers have been good substitute sources for swapping synthetic fibers and reinforcing polymer matrices because of their contributions in maintaining ecology, low energy requirement for processing, and maintaining sustainability issues. The aim of this study was to characterize a new fiber from Cyperus Dichrostachus A.Rich (CDA) plant. The CDA plant is a perennial nonwoody grass found in Ethiopian high lands and river basins. The fiber from this plant has a chemical composition of cellulose (60.27%), hemicellulose (22.72%), and lignin (16.59%) contents. It has a density of 1010 kg/m3 and good tenacity of 105.76 cN/Tex with low elongation of 4.88%. The thermal stability of Cyperus Dicrostachus A.Rich fiber (CDAF) was studied using TGA and DTG analyses and revealed that the cellulose degraded at a temperature of 377.1°C. Fourier transform-infrared spectroscopy analysis confirmed that CDAF is rich in cellulose content. Additionally, CDAF can play a vital role as a new reinforcement material and best alternative in bio composite industries. This will give competitive advantages when evaluated with other natural fibers and reveal that there are significant potential benefits in implementation of “cleaner production” in textile material production industries. Specifically, the replacement of synthetic fiber source with renewable biomass will reduce the environmental impact of these fibers. The future study will be focused on investigating the possible valorization route, especially in paper board, composite reinforcement, and bio composite applications.

An overview of mathematical modeling for conventional and intensified processes for extracting essential oils

Essential oils are extracted from plants by different methods, including traditional and emerging technologies. The so-called emerging technologies, such as extraction aided by microwaves and/or ultrasound, can improve heat and mass transfer, reducing processing times, energy requirements, and environmental impacts. Understanding the role of mass transfer and heating mechanisms in the performance of these intensified processes is critical for their efficient design. So far, several mathematical models have been developed to describe the effect of the different process variables involved in those extraction processes. This review aims to discuss the different models developed to describe the extraction behavior for both traditional and emerging technologies, identifying the theoretical basis, associated variables, and undertaken assumptions, intending to provide the readers with a helpful overview of the existing mathematical approaches and their feasibility for different applications.

Potential global GHG emissions reduction from increased adoption of metals recycling

Materials production is a significant contributor to greenhouse gas (GHG) emissions, and as consumption of commodities and resources continues to increase, so does the environmental footprint of extraction per unit of material. Primary production of metals has been progressing with steadily declining ore grades, resulting in higher energy requirements for extraction and processing of larger ore volumes bearing lower metal concentrations. Secondary production from recycled material stocks requires less energy than primary production and thereby has a lower GHG footprint. An LCA-based assessment of potential future adoption scenarios (Plausible, Ambitious, Maximum) of secondary production in the total global market for major commodity metals was conducted to identify the GHG emissions reductions possible from increased metal recycling and secondary production. The Plausible and Ambitious future scenarios result in 4.5 to 12 Gt of GHG emissions reduction globally from 2014 to 2050, and a Maximum future scenario results in over 42 Gt of GHG emissions reductions for the same period. The results of the analyses of the Plausible and Ambitious scenarios, though not close to maximizing use of total scrap available, clearly indicate that even small increments of improved metal recovery for secondary production have significant potential for GHG emission reductions. Analysis of material feedstock costs was also performed to assess the cost to producers of switching from virgin feedstocks to recycled materials.

Energy consumption and performance optimisation of laser cleaning for coating removal

Selective removal of coatings by lasers can facilitate the reuse of coated tools in a circular economy. In order to optimise and control the process, it is essential to study the impact of process input variables on process performance. In this paper, coating removal from tooling was carried out using a picosecond a pulsed fibre laser, in order to investigate the effects of laser pulse energy, pulse frequency, galvo scanning speed and scanning track stepover. A fractional factorial design of experiments and analysis of variance was used to optimise the process; considering cleaning rate, specific energy consumption and surface integrity as assessed by changes in surface roughness and composition of the tooling after laser cleaning. The results shows synergy between cleaning rate and specific energy with the laser pulse frequency and galvo scanning speed as the two most significant factors, while the laser pulse energy had the greatest contribution to changes in surface composition. Based on extensive experiments, the relationship between processing rate and system specific energy consumption was mathematically modelled. The paper contributes a new specific energy model for laser cleaning and provides a benchmark of the process energy requirements compared to other manufacturing processes. Additionally, the generic scientific learning from this is that the rate of energy input is a key tool for maximising cleaning rate and minimising specific energy requirements, while the intensity of energy applied, is a key metric that influences surface integrity. More complex factors, influence the surface integrity.

Systematic and efficient optimisation-based design of a process for CO2 removal from natural gas

Natural gas is an important resource for bridging technology on the way to mostly renewable power. A significant number of natural gas sources with high CO2 contents have not been exploited yet due to high cost of CO2 separation. Growth in global natural gas demand, however, has lead to re-evaluation of unconventional natural gas reserves. In this contribution, different hybrid processes for CO2 removal from natural gas are optimised with regard to minimum process energy requirements. Considered separation operations are cryogenic distillation, membrane separation, and physical absorption with methanol. The influence of a wide range of CO2 contents in the natural gas feed (40mol-% to 80mol-%) on different process alternatives is investigated. This is combined with limits for CO2 contents in the natural gas product varying from pipeline transport (2–3 mol-%) to LNG specification (50ppm). As a result, we provide an overview over which process topology is optimal for which combination of natural gas feed and natural gas product specifications. Process optimisation is performed using a framework for systematic optimisation-based process design which includes robust and computationally efficient reduced models for unit operations and hence enables automated performance of a large number of optimisation calculations.

Catalysing electrowinning of copper from E-waste: A critical review

Smart technologies and digitalisation have increased the consumption of scarce metals that threaten the sustainability of intricated industries. Additionally, the growing streams of waste electrical and electronic equipment (e-waste) are significant hazards to public health and the environment. Thus, there is an escalating need to recover metals from e-waste for sustainable management of metal resources. Hydrometallurgical processing of e-waste, involving copper (Cu) leaching and its subsequent recovery from pregnant leach solution (PLS) via electrowinning, has emerged as an efficient strategy to close the recycling loop. Electrowinning from PLS demonstrated higher Cu recovery efficiency and operational feasibility with a lower reagent use and lesser waste generation. Nevertheless, multiple issues challenged its practical implementation, including selective recovery of Cu from PLS containing mixed metals and high energy consumption. This review (1) identifies the factors affecting Cu electrowinning from PLS; (2) evaluates the composition of lixiviants influencing Cu electrowinning; (3) appraises various catalysts developed for enhancing Cu electrodeposition; and (4) reviews coupled systems that minimised process energy consumption. From the literature review, electrocatalysts are prospective candidates for improving Cu electrowinning as they reduced the cathodic reduction overpotentials, enhanced surface reaction kinetics and increased current efficiency. Other catalysts, including bioelectrocatalysts and photoelectrocatalysts, are applicable for dilute electrolytes with further investigations required to validate their feasibility. The coupled systems, including slurry electrolysis, bioelectrochemical systems and coupled redox fuel cells, minimise process energy requirements by systematically coupling the cathodic reduction reaction with suitable anodic oxidation reactions having thermodynamically low overpotentials. Among these systems, slurry electrolysis utilising a single-step processing of e-waste is feasible for commericalisation though operational challenges must be addressed to improve its sustainability. The other systems require further studies to improve their scalability. It provides an important direction for energy-efficient Cu electrowinning from PLS, ultimately promoting a circular economy for the scarce metal resources.

Optimization of Extraction Conditions for Cyperus Dichrostachus A. Rich Plant Fiber

The Textile industry is an important contributor to the GDP of countries worldwide. Both natural and synthetic fibers are the main raw materials for this sector. Environmental concerns, depletion of non-renewable resources, the high price of oil and limited oil reserves with consumer demand is driving research into cheap, biodegradable, sustainable, renewable and abundantly available green materials. Natural fibers are of the good substitute sources for swapping synthetic fibers and reinforcing polymer matrices because of their contributions in maintaining of ecology, nature of disposal, low energy requirement for processing and sustainability. The current research emphases on evaluating and determining the best extraction methods to process and treat cyperus Dichrostachus A.Rich plant in order to make the fiber suitable for variety of applications. Cyperus Dichrostachus A.Rich plant was treated with two conditions (cold and warm conditions) using statistically planned tests. Process conditions were optimised using central composite design methodology with the experimental design. Under optimised conditions, the strength and fiber yield of CDA fibers were significantly compared. The strength and fiber yield of the fiber was at maximized with optimized conditions and use for valorisation applications.

Comparing the energy requirements for amine absorption processes for CO2 capture from flue gases calculated using a minimal information simple thermodynamic model with experimental and detailed simulation results

The minimum and operating stripper reboiler duties for amine regeneration are estimated using a simple thermodynamic method that only uses the stripper pressure, the rich and lean loading of the sorbent and the temperature approach in the cold side of the crossflow heat exchanger. The thermodynamic model avoids the consideration of the complex CO2-sorbent chemistry and only requires CO2 partial pressure against solvent loading at ambient conditions, facilitating straightforward solvent evaluation. The results, presented mostly for 30 wt% MEA, are compared with modeling using Aspen Plus V10, detailed models presented in the literature, and pilot plant results. The thermodynamic model is a good predictor of pilot plant and simulation results except at low lean loadings when overstripping develops pinch conditions and undesirable high reboiler loads. Remarkably, as discussed before, the solvent heat of vaporization does not appear in the model. The model shows that the energy requirements are almost independent of the lean loadings except at the pinching limits and high-circulation under-stripping. In all cases the strong connection between the thermodynamic minimum and the experimental results reflects the high efficiency of amine processes and provides a useful reference when considering other sorbents and processes for CO2 capture.

Chemical looping reforming for syngas generation at real process conditions in packed bed reactors: An experimental demonstration

Chemical looping reforming (CLR) is a promising technology for syngas production combining autothermal operation with integrated CO2 capture. At large scale, reformer outlet pressure during syngas production is an important factor for the overall plant’s process efficiency and defines the energy requirements for downstream processing. Packed bed reactors are widely used and established in industry for high pressure operating conditions due to their robust and, compared to other reactor types, simpler engineering. In this paper, CLR in packed bed reactors (CLR-PB) is demonstrated under a pressure range of 1 – 5 bar in a lab scale reactor, using NiO/CaAl2O4 as the oxygen carrier (OC). Oxidation, reduction and dry reforming processes were examined in a wide range of temperature (400 – 900 °C), pressure (1 – 5 bar), flowrate (10 – 40 NLPM) and different inlet gas compositions, providing an important foreground for the optimal operating conditions for each process.Furthermore, a full CLR-PB pseudo-continuous cycle has been successfully demonstrated for the first time in a lab reactor setup. During the full cycle operation, CH4 conversion > 99% has been achieved, while the temperature and concentration profiles provided identical results for consecutive cycles verifying the continuity and the feasibility of the process. These results constitute the basis for the scale-up of the process, where heat losses would be minimized and the energy efficiency of the process would be significantly higher.

Integrated direct air capture and oxidative dehydrogenation of propane with CO2 at isothermal conditions

Developing routes of utilizing CO2 emissions is important for long-term environmental preservation, as storing such emissions underground will eventually become unsustainable. One way of utilizing CO2 emissions is as a light-oxidant feedstock for oxidative dehydrogenation of propane (ODHP) to propylene. However, the adsorption and reaction steps typically occur at widely different temperatures, meaning that the thermal gradients – and by extension process energy requirements – are often unreasonably high. In recent years, dual-functional materials (DFMs) – i.e., materials comprised of a high temperature adsorbent phase alongside a heterogeneous catalyst – have been employed for combined CO2 adsorption and utilization over one material within a single bed using a reduced thermal gradient. However, these materials have never been formed into practical contactors and have never been applied to ODHP applications. Therefore, in this study we manufactured the first-generation of DFM adsorbent/catalyst monoliths, comprised of CaO (adsorbent) and M@ZSM-5 (M = V-, Ga-, Ti-, or Ni-oxide) heterogeneous catalysts, using our novel direct metal-oxide 3D printing technique. The monoliths were vigorously characterized using N2 physisorption, C3H8-DRIFTS, NH3-TPD, Py-FTIR, H2-TPR, XRD, XPS, and elemental mapping and were assessed for CO2 capture/ODHP utilization at 600–700 ºC. The adsorption/catalysis experiments revealed that these materials can perform both processes effectively at 600 ºC, with reduced propylene yield at higher temperature, which eliminated the need for a thermal gradient between the adsorption and catalysis steps. Between the various samples, the Ti-doped monolith generated the best balance of CO2 conversion (76%) and propylene selectivity (39%), due to the high dispersion of TiO2, favorable redox properties and controlled acidity of the dopant. However, it was also found that varying the metal dopant could be used to control the heuristics of CO2/C3H8 conversion, C3H6 selectivity, and C3H6 yield, meaning that the manufacturing process outlined herein represents a promising way of tuning the chemical properties of structured DFM adsorbent/catalyst materials. More importantly, this study establishes a promising proof-of-concept for 3D printing as a facile means of structuring these exciting composite materials and expands DFMs to the previously unexplored application of ODHP.

Design of a water wash column in the CO2 capture process using a polyamine-based water-lean solvent

Amine-based water-lean solvents (WLSs) have been studied as energy-saving alternatives to existing aqueous amine solvents for the capture of CO2. However, despite the low energy requirements of WLS-based processes, WLSs are susceptible to amine vaporization loss due to the high amine concentration. In addition, the water content of WLSs is apt to increase, which is caused by the low vaporization pressure of water from the solvent due to the low water content of the solvent. When this happens, it is expensive to return the water content of the solvent to its original state. To address these problems, in this study, we investigated the design of a water wash section for a CO2 capture process based on a WLS consisting of 60 mass% of 3,3′-iminobis (N,N-dimethylpropylamine) (IBDMPA), 10 mass% of water, and a non-amine chemical as the final content. The heat and mass balance around the water wash section was analyzed, including the IBDMPA/water transfer from gas phase to liquid (water) phase within the water wash bed. To achieve this, the mass transfer coefficients of the IBDMPA and water were measured in a modified wetted wall column system, and the binary and ternary vapor–liquid equilibria for the WLS were also measured and modeled. The computation using the ASPEN Plus® simulator showed that IBDMPA emissions of less than 1 ppm and water balance in the WLS could be successfully achieved through the appropriate design of the water wash section.

Direct air capture of CO2: A response to meet the global climate targets

HighlightsDAC can help deal with difficult to avoid emissions. Large-scale deployment of DAC requires serious government, private, and corporate support and investment particularly to offset the capital cost as well as operational costs. Further optimizations to the costs can be found in choice of energy source as well as advances in CO2 capture technology such as high capacity and selectivity materials, faster reaction kinetics, and ease of reusability.Direct air capture (DAC) technologies are receiving increasing attention from the scientific community, commercial enterprises, policymakers and governments. While deep decarbonization of all sectors is required to meet the Paris Agreement target, DAC can help deal with difficult to avoid emissions (aviation, ocean-shipping, iron-steel, cement, mining, plastics, fertilizers, pulp and paper). While large-scale deployment of DAC discussions continues, a closer look to the capital and operational costs, different capture technologies, the choice of energy source, land and water requirements, and other environmental impacts of DAC are reviewed and examined. Cost per ton of CO2 captured discussions of leading industrial DAC developers with their carbon capture technologies are presented, and their detailed cost comparisons are evaluated based on the choice of energy operation together with process energy requirements. Validation of two active plants’ net negative emission contributions after reducing their own carbon footprint is presented. Future directions and recommendations to lower the current capital and operational costs of DAC are given. In view of large-scale deployment of DAC, and the considerations of high capital costs, private investments, government initiatives, net zero commitments of corporations, and support from the oil companies combined will help increase carbon capture capacity by building more DAC plants worldwide.Graphic abstract

Production of fuel grade anhydrous ethanol: a review

Alcoholic fermentation of fermentable carbon sources like molasses and table sugar using yeast are typical route in producing alcohol particularly known as bioethanol (C2H5OH). The key challenge encountered in bioethanol production process is to eliminate the impurity presence within the bioethanol which mainly water. Distillation is an energy extensive process which commonly used to recover ethanol up to 95% purity due to the presence of azeotropic composition. The distillation will no longer appropriate for further purification once the azeotrope composition has reached. Nonetheless, to be able to use as a viable fuel for gasoline engine or for any other utilizations where the purity is a major concern, further dehydration steps are needed producing an absolute ethanol. Few studies have been investigated on various dehydration methods for producing anhydrous ethanol, including azeotropic distillation, extractive distillation, adsorption, membrane pervaporation, and solvent extraction process. This review offers an insight into currently used technology on the ethanol dehydration methods and the future prospect on the continuous improvement particularly on the process energy requirement and efficiency will be discussed.