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Industrial energy management is critical to ensuring efficient energy usage, market viability, and greenhouse gas emission reductions. In this study, the aim is to investigate energy management practices in paper and pulp industries (PPI) of Bangladesh. The study identifies several barriers to adopt energy management practices; "Lack of governmental attention", "Inadequate staff awareness" and "limited access to capital" are identified as the major constraints. In addition, HVAC systems and compressed air systems present higher barriers compared to electrical motor and pump systems while looking at the barriers by technology areas. On the other hand, "Owner's demand", "Commitment from the top management" and "Pressure from the customers and different non-Governmental organization" are found to be the dominant drivers of energy management in the studied PPI. Energy management practices can enhance the energy efficiency approximately by 4–5 % according to the study. Furthermore, this study reveals that the majority of PPIs are unaware of the energy service companies (ESCO) with the lack of a standardized system for energy audit, as well as a lack of trust and information, appearing to be the obstacles behind this. • Energy management practices in paper and pulp industries of Bangladesh are shown. • Barriers and drivers to energy management practices in paper and pulp industry are presented. • Barriers to energy efficiency measures by technology area are discussed. • Barriers to consult energy service companies (ESCOs) are presented. [ABSTRACT FROM AUTHOR]

• The 2,4-dichlorophenoxyacetic acid is effectively removed by electrocatalytic oxidation. • By activating the lattice oxygen in Ni/WO 2 , a large amount of O 2 − is produced. • The electrocatalytic oxidation of 2,4-dichlorophenoxyacetic acid by Ni/WO 2 is the best at 8 mA cm-2. • The catalyst is simple to manufacture and has a low cost. Electrocatalysis is a promising method for removing harmful substances because it does not involve toxic agents and has low energy consumption. Herein, we have developed a low-cost nickel-tungsten dioxide (Ni/WO 2) grown on carbon paper for the first time. Ni/WO 2 /CP demonstrates remarkable catalytic efficiency for the electrocatalytic oxidation of 2,4-dichlorophenoxyacetic acid (2,4-D), achieving a conversion rate of 100 % within 3 h and a total organic carbon (TOC) removal rate of 57 %. After four reaction cycles, the electrode can still achieve a conversion rate of 90.49 %. The exceptional activity of Ni/WO 2 could be attributed to the activation of lattice oxygen in WO 2 by coupled Ni, leading to the generation of a significant amount of superoxide free radicals (O 2 −) and creating numerous oxygen vacancies that serve as the active sites for subsequent 2,4-D oxidation. This work highlights the impact of lattice oxygen on electrocatalytic oxidation and material modification, offering a noble metal-free catalyst for converting harmful substances. [ABSTRACT FROM AUTHOR]

Research has revealed the existence of an energy-efficiency gap – the difference between optimal and actual energy end-use, suggesting that energy efficiency can be improved. Energy management (EnM) is a means for improving industrial energy efficiency. However, due to various barriers, the full potential of EnM is not realised. Several studies have addressed drivers and barriers to energy efficiency but few to EnM. This study aims to identify EnM practices, the most important perceived drivers and barriers for EnM, and relations among them in the energy-intensive Swedish pulp and paper industry (PPI), which has the longest experience internationally of practising EnM systems, and has worked according to the standards since 2004. Our results show that, altogether, the PPI works regularly and continuously with EnM, with a clear division of responsibilities. The highest maturity for EnM practices was for energy policy, followed by organization, investments, and performance measurement. The study also shows that communication between middle management and operations personnel has potential for improvement. The most important categories of drivers were economic, whereas for barriers they were organizational. Nevertheless, knowledge-related barriers and drivers were amongst the most important, suggesting that the absorptive capacity for energy issues could be improved. Image 1029 • Energy is managed continuously, with clear policies and responsibilities. • The main drivers are economical while main barriers are organizational. • Knowledge related barriers and drivers are amongst the next most important. • Employees' absorptive capacity for energy issues could be improved. • Link between energy policy and performance measurement could be improved. [ABSTRACT FROM AUTHOR]

Guiding industries to produce in an effective and environmentally sustainable manner has become a key issue for governments around the world. Over the past 15 years, series of regional and industrial development policies have been introduced by the Chinese government. This has influenced the geographical distribution and energy efficiency performance of China’s industries. This paper quantifies the influence of enterprises geographical distribution on energy efficiency improvement in the paper industry and aims at providing some helpful suggestions on industrial development to policy makers. The main results show that, firstly, the paper industry in eastern China shows obvious characteristic of agglomeration. The average location quotient is 1.2278. However, following the industrial and regional development policies, the characteristic of agglomeration is weakening. Secondly, only when agglomeration reaches a certain level (location quotient is above 0.5447) will industrial agglomeration positively impact on industrial energy efficiency improvement (a 1% increase in agglomeration will increase dynamic energy efficiency by at least 0.23%). Thirdly, the regional development policies carried out by the government slow the pace of energy efficiency improvement in China’s paper industry. The empirical results indicate that the government needs to consider regional characteristics and consciously guide industrial enterprises to concentrate in the dominant area. [ABSTRACT FROM AUTHOR]

Abstract Papermaking enterprises are currently under both environmental pressure and economic pressure for sustainable development in China. Thus, the efficiency, effectiveness, and benefits of resource utilization need to be improved. High-consumption and high-pollution companies should manufacture paper using sustainable methods. This study highlights a resource value flow analysis from the circular economy perspective, developing an extension of material flow cost accounting and modifying it by accounting for environmental damage as well as economic benefits. With reference to the Plan-Do-Check-Act cycle, this specific case study was conducted to verify the comprehensive utility of resource value flow analysis by establishing decision-making prioritization according to the dualistic diagnosis of "internal resource loss–external environmental damage costs." In general, applying a resource value flow analysis can both reduce resource consumption and minimize environmental damage, enhancing the sustainable development of a process industry with limited resources. Highlights • Material flows and value flows form an interactive unit in the resource value flow analysis model. • The resource value flow analysis model extends the environmental dimension of material flow cost accounting. • A dualistic diagnosis of "internal resource loss and external environmental damage costs" can achieve both economic profits and environmental benefits. • The Plan-Do-Check-Act cycle was introduced to strengthen the practical application of the resource value flow analysis. [ABSTRACT FROM AUTHOR]

The current challenge facing the European pulp and paper industry is how to materialize the transformation to a bio-economy, as well as to realize the necessary new green innovations. The risks, costs and constraints of doing business will increase, thereby further intensifying competition, but at the same time new business opportunities will open up. This study adopts a three-round dissensus-based Delphi approach in order to explore our key research question of how the pulp and paper industry may change strategically, and what is the potential for value creation in the year 2030. According to our expert panel, the main drivers of competitiveness in 2030 will include energy and material efficiency, sustainability, as well as new innovations in products to serve customer needs better. According to the projected 2030 scenario, the pulp and paper industry will produce more diversified products, focus on higher value-added, and aim at consumer segments with higher environmental awareness. On average, 40 percent of the turnover will according to the panel come from genuinely new products. Strategic cross-sectorial partnerships will have a key role in making this big leap, while simultaneously acknowledging the changing needs of sustainability-conscious customers and other stakeholders. [ABSTRACT FROM AUTHOR]

China is the top emitter of greenhouse gases in the world. Pulp and paper industry is one of eight the strictly regulated industries about carbon emission in China. However, estimates of carbon emissions from China's pulp and paper industry have been suffered from remarkable uncertainty. It is summarized that is aroused by the inaccuracy of factors evaluating energy consumption, and the huge gap between the calculation standards for assessing energy consumption in the production process and the actual level recorded in the factories. This paper re-evaluated the carbon emission of China's pulp and paper industry from the perspective of life cycle assessment, and applied more accurate emission factors, taking account of the actual energy consumption of the production process in factories, to estimate the actual carbon emissions in maximum. It is found that the national standards about the energy consumption quota of China's pulp and paper industry is no longer applicable, and the actual energy consumption regulated in the production process is far better than the advanced level given by the national standards. The greenhouse gas emission have been seriously overestimated approximately 12.00%–56.17% by international organizations. • Life Cycle Analysis of the China's pulp and paper Industry is conducted thoroughly. • The pulp flow of China's pulp and paper Industry is analyzed. • Energy regulated in factory is far better than the national standards' required. • Carbon emissions of China's pulp and paper Industry are overestimated. [ABSTRACT FROM AUTHOR]

With the surging energy price and environmental concerns, measures to improve energy efficiency have attracted increasing concerns of the manufacture sector, especially energy-intensive manufacturing industries such as tissue paper mills. Energy-efficiency scheduling, as a novel energy-efficient method, has attracted the attention of an increasing number of researchers in recent years. Drying process is the most energy-intensive production process in tissue paper mills, which has a great energy-saving potential. This paper aims to reduce the energy costs for the tissue paper mill, consisting of processing energy cost and set-up energy cost, through integrating drying process optimization with energy-efficient scheduling. First, the energy cost model and the scheduling model were built. Then, the energy cost of the drying process of every job in a given scheduling problem was optimized using particle swarm optimization (PSO). Afterwards, the energy cost was further optimized using energy-efficiency scheduling. In addition, a hybrid non-dominated sorting genetic algorithm II (NSGA-II) was utilized to solve the energy-efficiency scheduling problem. Finally, several real scheduling problems from a real tissue paper mill were addressed using the proposed approach to demonstrate its effectiveness in energy saving. The experiment result showed that there is a great energy-saving potential in the drying process, accounting for up to 12.53% of the total energy consumption. Moreover, the maximum energy saving ratio of the proposed approach could reach 9.03%. On the whole, the proposed approach can provide a new energy-saving method for tissue paper mills or other manufacturing industries. [ABSTRACT FROM AUTHOR]

In recent years, the pulp and paper industry has changed a lot and products have been constructed in quite different methods using new technologies. It can be due to the emergence of challenges and constraints such as shortage of raw materials, energy consumption (fossil fuels, electric, etc.), management of the resulting pollutants, environmental issues, ongoing legal requirements and cleaner production strategies. In Iran, the pulp and paper industry's technological development is not keeping pace with global growth. Iran's pulp and paper mills supply a small fraction of domestic market. The reasons can be due to old technologies being used in factories, aging machinery, low productivity of production systems and lack of coordination with modern technologies. It leads to low-quality of paper products and willingness to buy local products. The aim of this study is to select the most appropriate technologies in the pulp section, due to high impact of pulp quality on the quality of final paper. Using a 2-filterd fuzzy decision-making, hierarchical structure of research is designed to assess technological alternatives according to the selected criteria. Findings show that after passing through two filters, Kraft method was chosen as the most appropriate method. The Kraft process has still many advantages like the high quality of the produced pulp and self-sufficiency in energy supply. This framework offers an appropriate procedure for identifying and selecting technologies that has not been used in past researches. Using this framework facilitates using a clear procedure for evaluating and selecting technology and prevents future losses for organizations. [ABSTRACT FROM AUTHOR]

China's paper industry accounts for a larger proportion of the global paper industry and consumes large amounts of energy. Energy conservation and pollution reduction of the industry have become the focus of China's national development strategy. Energy efficiency is an important index which directly determines the amounts of energy consumption and pollution emissions. To understand the energy efficiency evolution of China's paper industry, this paper establishes an input-output data of the paper industry for 29 provinces in China and applies DEA method and econometric models to estimate and comprehensively discuss the energy efficiency issues based on the framework of total factor efficiency. Our results indicate that China's paper industry has a large energy saving potential even though its energy efficiency has improved during the period 1990–2013. The saving potential is about 65% under the meta-frontier and 44% under the group-frontier. Moreover, there are significant differences between different regions in production technology and energy efficiency. The performance of eastern China is better than other regions. But the technology gaps between the different regions are shrinking and converging over time. Finally, some policy recommendations are proposed to improve the energy efficiency of the industry. [ABSTRACT FROM AUTHOR]

China’s paper industry consumes a lot of energy and emits huge amounts of pollutions. The Chinese government over the past decades has done a lot to promote energy efficiency of the industry. This paper studies the impact of industrial polices to improve energy efficiency. The energy efficiency change is firstly studied under a framework of total factor efficiency. On this basis, different econometric models are built to discuss the detailed energy efficiency characteristics of the paper industry. The main results are as follow: (i) ownership structure did influence the energy efficiency, but the influence is different in different conditions; (ii) energy efficiency of the paper industry can be improved by economies of scale; (iii) market competition can to some extent overcome the motivation and supervision problem that often occur in state-owned companies; (iv) energy price cannot play the role of resource allocation well in China. Finally, based on our findings, some suggestions are provided. [ABSTRACT FROM AUTHOR]

The increasing use of recycled paper by the paper industry to support the Green Industry in the Indonesian Pulp and Paper Industry. But technically, there are some disadvantages of recycled fiber usage such as low drainage rate in which boosted the high energy consumption on drying process. As already known, the drying process consumes the highest energy in papermaking. To overcome this problem, the research using the concentrate of endoglucanase Egl-II has done. The steps of research included production of endoglucanase Egl-II; concentration by ultrafiltration method, modification of recycled paper fibers using endoglucanase Egl-II; characterization of paper sheet; and evaluation of energy consumption in drying the sheet of paper. The results showed that endoglucanase Egl-II had increase drainage rate of recycled fiber stock, which indicate by the freeness number. The number had increased by 80 ml CSF (Canadian Standard Freeness) from 190 ml CSF to 270 ml CSF, and fiber retention increased by 0,63% from 99,31% to 99,94%. The dissolved cellobiose test results of recycled fiber stock by the enzyme treatment at low dosage showed that no degradation of cellulose, no change into soluble sugars. Characterization of sheet of paper that has been modified with endoglucanase Egl-II based FTIR spectra showed no change in functional group, SEM results showed on the fiber surface fibrils grow more, and the results of the XRD analysis showed area reduction of amorphous regions is about 6%. The potential for energy efficiency is calculated through thermodynamic approach is about 15%. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the effect of electrical conductivity, pH and temperature which were kept constant during treatment via an advanced control strategy on chemical oxygen demand, color, turbidity and total suspended solids removal and energy consumption. Central Composite Design matrices were formed for aluminum and iron electrode systems separately with different combinations of 5 independent variables (electrical conductivity, pH, temperature, current intensity and electrolysis time). Obtained results revealed that aluminum electrode system was found to be more effective than iron electrode system under controlled conditions. Comparison of uncontrolled and controlled studies at optimum values of aluminum electrode system showed an increase by 31.67% in chemical oxygen demand removal and a decrease by 48.30% in energy consumption under controlled case. Results indicated that constant electrical conductivity, pH and temperature during electrocoagulation process of pulp and paper mill wastewater by means of a controller enhanced treatment efficiency. [ABSTRACT FROM AUTHOR]

Renewable energy production throughout low-voltage grids has gradually increased in electrical distribution systems, therefore introducing small energy producers - prosumers. This paradigm challenges the traditional unidirectional energy distribution flow to include disperse power production from renewables. To understand how energy usage can be optimized in the dynamic electrical grid, it is important to understand the behavior of prosumers and their impact on the grid's operational procedures. The main focus of this study is to investigate how grid operators can obtain an automatic data-driven system for the low-voltage electrical grid management, by analyzing the available grid topology and time-series consumption data from a real-life test area. The aim is to argue for how different consumer profiles, clustering and prediction methods contribute to the grid-related operations. Ultimately, this work is intended for future research directions that can contribute to improving the trade-off between systematic and scalable data models and software computational challenges. [ABSTRACT FROM AUTHOR]

China has become the world largest paper and paperboard producer. However, pulp and paper industry has involved high resource consumption and severe pollution especially for water. This research has assessed the eco-efficiency of China's pulp and paper industry at the national level and provincial level. An overview regarding the cleaner production of China's pulp and paper industry was presented to reveal the measures for reducing environmental impact in the last two decades. Slacks-based measure was used to analyze the efficiency levels of 16 provinces' pulp and paper industries. To uncover the underlying causes of eco-efficiency performance, Malmquist–Luenberger index was calculated to discover the drivers of productivity growth of pulp and paper industries. Our results showed that the pollution treatment of China's pulp and paper industry has made progress in terms of water consumption and water pollution, although the absolute amount of pollution discharge is still large. Chemical oxygen demand emissions are still the first critical influencing factor of pulp and paper industry's inefficiency. Furthermore, efficiency progress was the dominating contribution of the industry's productivity growth between 2010 and 2013. The policies for adjusting the industrial structure of pulp and paper industry have resulted in the scale effects through eliminating backward production capacity and accelerating merger and acquisitions. Moreover, the productivity of pulp and paper industry was underestimated when the undesirable outputs were ignored. It indicates that the stricter environmental regulations have positive effects on paper companies to internalize environmental pressures in the production activities through environmental management. In the future, pulp and paper companies should further internalize the cost of pollution treatment through scale effects and technology improvement. [ABSTRACT FROM AUTHOR]

The pulp and paper industry accounts for approximately 5% of total industrial energy consumption and contributes 2% of direct carbon dioxide (CO 2 ) emissions from industries. World paper and paperboard demand and production are increasing significantly, leading to an increase in this sector's energy use and CO 2 emissions. Although current studies identify a wide range of energy-efficiency technologies that have already been commercialized for the pulp and paper industry, information is limited or scattered regarding new energy-efficiency technologies that are not yet fully commercialized. Development of emerging or advanced energy-efficiency technologies and their deployment in the market will be crucial for this industry's mid- and long-term energy saving and climate change mitigation strategies. This paper compiles available information on energy savings, environmental and other benefits, costs, and commercialization status for 25 emerging technologies to reduce the energy use and CO 2 emissions. The purpose is to provide a well-structured comprehensive review on these emerging energy-efficiency technologies for engineers, researchers, investors, policy makers, pulp and/or paper companies, and other interested parties. [ABSTRACT FROM AUTHOR]

Abstract With the advent of the Paris Climate Agreement and China ratifying it recently, there is a need to adopt a diversified approach to address climate change; this is especially the case of promoting residential energy conservation. This study is one of the first household energy intervention studies that focuses on the comparison of two message delivering means, paper-based versus instant messaging tool, as a platform for sharing energy-saving tips and engaging households to save energy in China. Conducted in several communities in Hangzhou, Zhejiang Province of China, the effectiveness of using a widely used application known as WeChat in promoting household energy conservation is compared with that of using stickers. It was found that WeChat is the most effective is reducing monthly consumption, but the effects are short-lived. Comparatively, using stickers as a mean of engaging households produces more sustained results in terms of energy savings. This study also provides evidence to correlate the changes in energy consumption behavior with personal perception of one's responsibility and quality of life. That is, certain behavior can be triggered if residents are willing to impose energy ration in their households or are given more opportunities in the form of local programs that enable them to have more practices in energy conservation. [ABSTRACT FROM AUTHOR]

Pulp and paper mill effluent (PPME), a rich cellulosic material, was found to have great potential for biohydrogen production through a photofermentation process. However, pretreatments were needed for degrading the complex structure of PPME before biohydrogen production. The aim of this study was to gain further insight into the effect of an ultrasonication process on PPME as a pretreatment method and on photofermentative biohydrogen production using Rhodobacter sphaeroides NCIMB. The ultrasonication amplitudes and times were varied between 30–90% and 15–60 min, respectively, and no dilution or nutrient supplementation was introduced during the biohydrogen production process. A higher biohydrogen yield, rate, light efficiency and COD removal efficiency were attained in conditions using ultrasonicated PPME. Among these different pretreatment conditions, PPME with ultrasonication pretreatment employing an amplitude of 60% and time of 45 min (A60:T45) gave the highest yield and rate of 5.77 mL H 2 /mL medium and 0.077 mL H 2 /mL h, respectively, while the raw PPME without ultrasonication showed a significantly lower yield and rate of 1.10 mL H 2 /mL medium and 0.015 mL H 2 /mL h, respectively. The results of this study demonstrated the potential of using ultrasonication as a pretreatment for PPME because the yield and rate of biohydrogen production were highly enhanced compared to the raw PPME. Economic analysis was also performed in this study, and in comparison with raw PPME, the highest net saving was $0.2132 for A60:T45. [ABSTRACT FROM AUTHOR]

The Swedish pulp and paper industry (PPI) must increase energy efficiency to remain competitive on the global market, which has experienced entries from countries with cheaper energy and raw material supplies. Interactions among variables for energy use, production, energy management, electricity price and firm characteristics (FC), in different types of mills, i.e., pulp, paper and integrated mills, in Sweden from 2006 to 2015 indicate that correlations among the studied variables were different in different types of mills. This difference between types of mills seemed to originate partly from varying accessibility to production residue that could be used for energy. For all types of mills, variation of electricity prices did not correlate significantly with energy efficiency during the study period. The studied FC were firm's age, number of employees, number of companies in company group, net sales and profit for the year. Energy efficiency was more affected by the variables characterizing energy and production compared to the variables representing FC. This study also suggested presence of possible discrepancies between FC that were perceived as barriers to energy management towards energy efficiency, according to previous studies, and what was shown by the data combining variables representing energy use, production and FC. [ABSTRACT FROM AUTHOR]

Abstract: There is a large value in making Pulp and Paper mills more energy efficient. ABB has developed an energy assessment service where opportunities to save energy in the paper machine are identified. The energy assessment is done by quantifying energy flows, benchmarking energy users, data mining and steam sensitivity analysis and by experiments and additional measurements at the paper machine. Energy quantification helped in identifying main energy consumer, benchmarking was useful to assess the gap between operating performance and best performance whereas data mining and steam sensitivity analysis helped in studying the impact of key operating variables on performance of paper machines. After the assessment an action plan was presented to the mill for energy efficiency improvement together with a return on investment. [Copyright &y& Elsevier]

Abstract: This work analyzed the energy flow of the pulp and paper industry in Taiwan. The potential technology options that were examined focus on how to capture some of the energy currently lost in the processes and then identifying the areas with energy-saving potential that could also have large impacts across a variety of industries. In addition, the energy-saving potential of these options was evaluated. The energy-saving potential of the pulp and paper industry would be around 6939.9 KLOE/M. The greatest energy-saving potential lies with improving energy distribution and equipment efficiency, which would together potentially comprise 86.8% of total energy conservation. This analysis can serve as a benchmark for current pulp and paper making operations, and as a base case for stimulating changes toward more efficient energy utilization in the pulp and paper industry. [Copyright &y& Elsevier]

Abstract: This article introduces a bottom-up global model of the pulp and paper sector (PULPSIM) with a focus on energy consumption and carbon emissions. It is an annual recursive simulation behavioural model with a 2030 time horizon incorporating several technological details of the industry for 47 world regions. The long time horizon and the modular structure allow the model users to assess the effects of different environmental, energy and climate policies in a scenario comparison setup. In addition to the business as usual developments of the sector, a climate commitment scenario has been analysed, in which the impacts of changing forest management practices are also included. The climate scenario results reveal that there is a significant carbon reduction potential in the pulp and paper making, showing a number of specific features: the central role of the fibrous resource inputs and the potential impact of increased waste wood and black liquor based heat generation. [Copyright &y& Elsevier]

Paper industry is one of major material and energy users in Finland, material costs being far bigger than energy costs. Energy saving is promoted in Finland by an energy service centre, subsidies and energy service companies (ESCOs). Material savings in production processes are typically used to reduce costs while life cycle material efficiency rather would require focusing, e.g. on product design. This could be promoted by total producer responsibility, economic instruments and environmental permits. For industrial sites with limited resources, MASCOs’ (Material Saving Companies) services could manage material savings, e.g. by funding the investments, planning and running the project. Authorities should put more emphasis on material auditing and information on material saving technologies and logistics. Material savings should also be included into the environmental permitting procedures. Materials saving services are developing and the projected Finnish material efficiency service centre could support new businesses. This article is based on a literature review and interviews of persons in paper producing companies and environmental authorities. We also analyse experiences of the first MASCO project in Finland. [Copyright &y& Elsevier]

Abstract: The aim of the study is to model and to simulate the thermal and electrical efficiencies of the cogeneration plant of a paper mill. The final purpose is the benefits optimization by adjusting production to the amount of energy to be sold. It is necessary to know it because the sale price goes down when the actual production of electrical energy does not match the scheduled power. [Copyright &y& Elsevier]

Abstract: In this study, a pulp and paper mill (PPM) in the SEKA Papermaking Plant in İzmit, Turkey, is analysed through energy and exergy balances. The plant utilises recycled waste paper for papermaking. This type of raw material input makes the process highly sophisticated. The pulping uses strictly mechanical processes, such as digestion, separation by screening and hydrocyclone, and refining. The milling, as an integrated process, provides the final operations necessary to prepare the conditions required for the end-product by stock-preparation, wiring, rolling, and drying by dewatering, pressing, and evaporation. The possibility of making the entire process more thermodynamically efficient is discussed by calculating the energy and exergy losses for all the mechanical and physical sub-processes. The study shows that the energy efficiencies for each of the mechanical and physical steps in the PPM vary between 34% and 97.4%, whereas the exergy efficiencies vary between 30.2% and 94.2%. In conclusion, based on the results from the energy and exergy flow analyses, the exergy output can be improved through more efforts directed primarily to further measurements toward more efficient energy utilisation in the PPM. [Copyright &y& Elsevier]

Abstract: A novel carbon paper electrode coated with supported tungsten trioxide is developed to improve the carbon fiber’s electrochemical performance toward the vanadium redox couples. Super activated carbon supported tungsten trioxide (WO3/SAC) is prepared via an impregnation method and characterized by X-ray diffraction and scanning electron microscopy. The electrochemical performance of the prepared electrode is evaluated with cyclic voltammetry and electrochemical impedance spectroscopy. Results show that WO3/SAC exhibits excellent electro-catalytic activity and kinetic reversibility toward the vanadium redox couples. By adding the WO3/SAC, the charge transfer resistances for both the positive and the negative reactions are significantly reduced. Using as prepared electrodes, the columbic efficiency (CE), voltage efficiency (VE) and energy efficiency (EE) of the vanadium redox flow battery at 50 mA cm−2 are 94.5%, 85.2% and 80.5%, respectively, which are much higher than that of the cell assembled with pristine carbon paper electrodes. [Copyright &y& Elsevier]

Abstract: This study considers different alternative uses of secondary heat in a mechanical pulp and paper mill. The considered alternatives are (1) three different heat exchanger network retrofits, (2) drying of bark, (3) drying of primary and activated sludge and (4) drying of both bark and sludge. The data has been gathered from an operating mill and a simulation model has been built to examine the mill-wide effects of the proposed changes. Targets for steam and cooling water use, used in the heat exchanger network retrofits, have been evaluated using pinch analysis. The amount of available secondary heat found in the pinch analysis can be used in drying of bark or sludge. Sludge is typically burned together with mill fuel in the bark boiler of a power plant to deliver heat and electricity to the mill. These wood-based biofuels typically consist of 50%w.b. water, which will evaporate and consume some of the fuel''s energy content during combustion. Fuel drying is a way to increase the heating value of fuels and to increase the energy efficiency of heat and power production. The utilisation of low-temperature secondary heat in the drying may reduce the need for fuels and primary energy in the mill. The different ways of using the secondary heat have different effects on primary fuel consumption and electricity production. Therefore the different results are compared using the reduction of CO2 emissions as a common criterion. The results show that all the considered alternatives have great energy-saving potential up to 8MW steam use in winter and 6MW in summer time. [Copyright &y& Elsevier]

Abstract: The objective of this paper is to estimate the energy saving potential in China's paper industry by determining energy intensity under different scenarios. Cointegration model and stability test are applied to formulate the equilibrium equation. Results show that energy price, industry structure, profit margin and technology have significant impact as they are negatively correlated to changes in energy intensity. Three scenarios (BAU (business as usual), intermediate and active) are designed to estimate the future trend of energy intensity in paper industry. In 2010, the energy intensity (energy consumption per unit of value added) was 4 tce/10,000 RMB, and by the scenarios it is expected to considerably decline. According to the BAU (business as usual) scenario, the energy intensity will decrease to 2.56, 1.43 and 0.70 tce/10,000 RMB by 2015, 2020 and 2025, respectively. With respect to the intermediate scenario it is expected to drop further to 0.44 tce/10,000 RMB. Yet by the active scenario, the energy intensity is expected to considerably decline to 0.36 tce/10,000 RMB by 2025. Using the BAU forecast as a baseline, the quantity of energy savings is estimated to be 185.6 billion tce by 2025. Considering this important potential, we also provided some policy suggestions. [Copyright &y& Elsevier]

Highlights: [•] Estimation of GHG emission and energy consumption in wastewater treatment plants. [•] On-site and off-site emissions of carbon dioxide, methane, and nitrous oxide. [•] Higher GHG emission in anaerobic and hybrid plants due to higher CH4 generation. [•] Recovery and use of biogas satisfy the energy demands of treatment systems. [•] Higher off-site than on-site GHG emissions due to the use of fuel and material. [ABSTRACT FROM AUTHOR]

The pulp and paper industry is a high energy consuming and polluting sector, and carbon emissions emitted from this sector are worthy of attention. This article, based upon an analysis of China’s Pulp and Paper Industry (CPPI), provides estimates of each of the following: carbon emissions from energy consumption, pre-treatment sector, combustion of condensed black liquor, and methane emitted from incomplete aerobic digestion during sewage treatment of CPPI. During the study period (2005–2012), total CO 2 emissions ranged from 126.0 Mt to 155.4 Mt. Energy consumption was estimated to be the largest source of carbon emissions, however, due to the application of the local emission inventory rather than the IPCC inventory, energy consumption decreased by 4.7%, a lower percentage than was calculated in a previous study. According to this study’s estimation, the emissions caused by the recovery of biomass energy contributed 26–29% of the total CO 2 emissions. CH 4 generated from sewage treatment accounted for 9–11% of the total carbon emissions. The CO 2 intensity dropped during the study period, which reflected the improvement of energy efficiency in the pulp and paper industry. The outcome of this study provides not only detailed information about CPPI’s carbon emissions, but also a calculation framework for studying carbon emissions from pulp and paper sector in the other regions. It suggests that the local carbon emissions inventory should be used for estimating carbon emissions and to reduce the fossil fuel energy, increase energy recovery from biomass, and that promoting cleaner production is essential to achieve a low carbon development of the pulp and paper industry. [ABSTRACT FROM AUTHOR]

Abstract: A great interest has been arising about the production of fuels and advanced chemicals from renewable resources such as wooden biomass in the so-called biorefineries. Pulp and paper mills are often seen as the most obvious fundamental module of such industrial sites, because of the common feedstock and the chemical transformations that already occur in the process. In this paper the model of real Kraft pulp and paper mill is developed and optimized from energetic point of view using process integration techniques, in order to assess the potential for energy saving and to establish a starting point for future research on biorefinery sites. Improvements to the configurations of the multi-effect evaporator and of the steam cycle in the CHP system have been introduced, and three different levels of heat integration boundaries have been considered (multi-effect evaporator, mill sub-processes, and total site). Results indicate a significant potential for the decrease in thermal energy requirement and/or the increase in power production for the same pulp and paper production. [Copyright &y& Elsevier]

Abstract: The need for more rational use of water also calls for more efficient usage. An example is the production of tissue paper, where large amounts of water are discharged into the drain because its turbidity does not allow for recirculation. While this is a serious problem, even worse is the fact that the quality of such wastewater makes it difficult not only to recirculate but also to discharge due to environmental law restrictions. In this paper, electrocoagulation is proposed as a suitable technology to meet standards of water discharge, and even better, as a treatment option for removal of turbidity. Since energy consumption has been a drawback for EC applications, relevant aspects that contribute to increase it such as cell voltage and current density have been reviewed. For this purpose a systematic micro-electrolysis study combined with macro-electrolysis experiments have provided evidence that shows it is possible to achieve a turbidity removal of 92% with an energy consumption of 0.68kWh/m3. Thus, the results presented in this paper support the use of EC to obtain water of acceptable quality for reuse in the tissue paper industry. [Copyright &y& Elsevier]

Abstract: The pulp and paper industry is one of the most energy-intensive industries worldwide. In 2007, it accounted for 5% of total global industrial energy consumption and 2% of direct industrial carbon dioxide (CO2) emissions. An energy audit is a primary step toward improving energy efficiency at the facility level. This paper describes a plant-wide energy audit aimed at identifying energy conservation and CO2 mitigation opportunities at a paper mill in Guangdong province, China. We describe the energy audit methods, relevant Chinese standards, methods of calculating energy and carbon indicators, baseline energy consumption and CO2 emissions of the audited paper mill, and nine energy-efficiency improvement opportunities identified by the audit. For each of the nine options, we evaluate the energy conservation and associated CO2 mitigation potential. The total technical energy conservation potential for these nine opportunities is 967.8terajoules (TJ), and the total CO2 mitigation potential is equal to 93,453tonnes CO2 annually, representing 14.4% and 14.7%, respectively, of the mill’s total energy consumption and CO2 emissions during the audit period. [Copyright &y& Elsevier]

[Display omitted] • Ultrafine marble dust waste particles were obtained using the top–down approach. • Waste and by-products had positive effect on dry grinding of stone wastes. • It is economically feasible, also environmentally friendly. • These obtained ultrafine particles can be used effectively mineral filler in many areas. Waste management in marble processing plants is a considerable problem in countries with developed stone industries and trade. Research on the utilization of stone waste in different fields is still continuing. However, there are few studies on using this stone waste from processing plants as mineral fillers. Moreover, no study in the literature has investigated the influence of grinding aids on stone properties. The current research is the first to compare of the efficiency of different grinding aids on the waste calcitic and dolomitic marble in the production of mineral fillers. The objective of this work is to research the impacts of waste and by-products on the dry grinding of stone wastes as grinding aids in a vertical stirred media mill. The results were assessed in terms of various parameters: product particle size, powder flowability, material coating on the grinding media, and energy consumption. Remarkably, the study showed that the use of any of the grinding aids tested enhanced the grinding process in comparison with the no-aid condition. The best product fineness value was achieved with pomace oil followed by the by-product glycerin, among the grinding aids tested in both samples. Moreover, a higher media coating reduction and the highest energy saving were achieved with pomace oil. The most significant and lowest increase in the fluidity index was achieved with pomace oil and paper wastewater, respectively. Additionally, the Fourier transform infrared spectroscopy (FTIR) performed to reveal the interaction between particle surfaces and grinding aids demonstrated the activity of pomace oil and glycerin polar functional groups on particle surfaces. The analysis of the agglomeration phenomenon with SEM (scanning electron microscopy) micrographs showed that particle agglomeration could be eliminated with the pomace oil. Thermogravimetric analysis (TGA) was used to investigate changes in the mass of the samples' due to temperature changes. With this study, a significant contribution will be made to the ecosystem using waste marble powder whose storage problematic. [ABSTRACT FROM AUTHOR]

Abstract: The systematic, transparent and accurate on-line energy information of the production process is quite the basis of mill energy management and conservation. An Energy Management System (EMS) was built according to the characteristics of the energy usage in a typical newsprint paper mill. The EMS first realized the process data acquisition and integration, second fulfilled the on-line energy information calculation from the integrated data. A water and steam properties query component based on IAPWS-IF97 was developed and plugged into the EMS to facilitate the energy calculation of water and steam. The practical performance in the paper mill showed that the integrated energy information of the whole mill was gained and the on-line energy supervisory was achieved. In the end a systematic, transparent and accurate energy usage profile is obtained and it would provide the valuable fundamental energy data for the further energy analysis and optimization in the EMS. [Copyright &y& Elsevier]

[Display omitted] • The effluent of the pulp & paper industry was treated by forward osmosis process. • Specific energy consumption (SEC) was lowest for fertilizer-based draw solution. • Low value of SEC obtained as 0.17 kWh/m3 in FO process using urea as draw solute. • Lower solute flux was observed for FO runs compared to RO and NF under same feed. • At higher draw solution concentration dradual increase of resistance was minimum. Wastewater treatment via suitable routes is necessary to protect the environment and fill the shortage of freshwater. An osmotic pressure-driven membrane separation process of forward Osmosis (FO) has gained attention as an alternative water treatment process over the conventional approaches. FO process needs a draw solution (DS). A commonly used fertilizer such as urea in water can be used as a DS, and after the FO run, diluted DS may use as fertilizer. Thus, it can simultaneously generate freshwater for agricultural purposes from industrial wastewater. FO process using thin-film composite flat sheet membrane has been investigated for various lab-made solutions and pulp & paper industrial effluent as feed solutions (FSs) under varying DSs of 0.25, 0.5, 1, and 2 M urea solutions. Limited FO studies examined the long-term and repetitive runs using the same membrane to access the fouling, water, and solute flux behavior with real industrial wastewater as feed solutions (FS). The long-term experimental results prove the strong influences of DS concentration on specific energy consumption (SEC), fouling behavior, and water flux. Increasing the cross-flow rate from 0.33 to 1 L/min has a minor effect on water flux, but SEC increases significantly from 0.17 ± 0.01 kWh/m3 to 0.50 ± 0.03 kWh/m3. FO runs show that the overall water flux enhances due to higher osmotic pressure difference and lesser membrane fouling at higher DS concentration using pulp & paper industrial secondary effluent as FS. This study demonstrates that a low-energy FO process can recover water from industrial wastewater while simultaneously produces a diluted fertilizer for fertigation. [ABSTRACT FROM AUTHOR]

Small area femtocell increases the energy efficiency of the cellular network as the distance between base station and user is very less. Mobile femtocell causes the spectrum reuse to be used at very large extent making spectral efficiency suffer. This paper discusses recently researched techniques that have been used to increase the spectral efficiency in mobile femtocell network. But these techniques also come with their own limitations. Considering this, data aggregation and compression technique can be consider as one of the best contender to increase the spectral efficiency in cellular network which is also been explained in this paper. [ABSTRACT FROM AUTHOR]

Abstract: In this study the possibilities of making a cost-effective heat exchanger retrofit in a simulated thermo mechanical pulp and paper mill are analysed using advanced composite curves. The use of advanced composite curves is a fairly new method developed in Chalmers University, and they have not previously been used to analyse a mechanical pulp and paper mill. The simulated mill used as an example in this study has one TMP (thermo mechanical pulping) line, one paper machine, debarking and auxiliary systems. The results show that the advanced curves give valuable information on the system and provide guidance as to where to look for improvement potential. The relative costs of different improvements are in line with traditional knowledge of improvement costs. [Copyright &y& Elsevier]

The pulp and paper industry faces several challenges linked to climate and environmental impact, resource efficiency, rising energy prices, increased competition for biomass resources, and declining demand for traditional printed paper products. However, these challenges also offer strategic opportunities for the industry to develop into a competitive, resource-efficient, and low-carbon industry in line with a biobased economy. Against this background, this paper aims to analyse current energy strategies in the pulp and paper industry in Sweden. Specifically, the paper analyses how companies combine continuous process efficiency to reduce energy costs with activities that could be developed into new energy-related products to increase revenue. Most of the analysed companies work to various degrees with both these strategies, employing methods that include improving energy efficiency, energy security, and energy conversion, as well as developing a wide range of biobased energy products. However, our study indicates that there is an untapped potential associated with energy product development, and we conclude that energy efficiency measures can free up resources, enabling the development of new energy products. Finally, several potential managerial outcomes and implications are outlined. • The paper analyses the energy strategies in the pulp and paper industry in Sweden. • Energy strategies focus both to improve energy efficiency and develop new energy-products. • The companies' energy strategies combined exploitation and exploration. • A number of managerial implications are presented. [ABSTRACT FROM AUTHOR]

Cogeneration is considered as one of the promising energy efficient techniques for producing electricity and useful thermal energy from a single fuel source. This paper describes a feasibility study of the implementation of different cogeneration options to a paper mill to evaluate their energy saving potentials and economic benefits. The investigated systems in this paper are gas turbine, steam turbine and combined cycle cogeneration options evaluated and compared based on energy utilisation factor and Annualised Life Cycle Cost (ALCC) analysis. The results of energy analysis show that all Combined Heat and Power (CHP) systems satisfy the thermal energy needs of the mill while the combined cycle cogeneration option generates the highest amount of electric energy equal to 10.91 MW. The gas turbine cogeneration system is shown as the most advantageous system from overall energy point of view with the highest energy utilisation factor of 78% meeting the heat and electric requirements of the mill and exporting 21,329 MWh of additional electricity to the grid. Economic feasibility results also show that an overall saving of 5.12 million US$ can be achieved by implementing the gas turbine cogeneration system to the mill making it as the best cogeneration option with the least overall ALCC of 1.34 million US$ and the maximum percentage of CO 2 emission reduction (68%) when compared with the other options. [ABSTRACT FROM AUTHOR]

Security token offerings (STOs), based on blockchain technology, are attracting increasing attention as an innovative alternative means of venture financing. Information about specific STOs is generally provided in white papers. This study analyses the content of white papers using a unique sample of 188 STOs from 2017 to 2021 to identify which topic is related to campaign success. We leverage latent Dirichlet allocation (LDA) topic modelling to identify the topics and themes in white papers. Nine topics are identified through LDA: company description, distributed ledger technology components, energy and green issues, financial and legal issues, artificial intelligence, and tech applications in different industries—specifically, healthcare, manufacturing and construction, education, and financial services. We find that energy and green issues represent one of the most prominent topics among all types of projects and that their disclosure is positively related to the probability of campaign success and the amount of funding raised. Another prominent topic that affects campaign outcomes is technology in the healthcare industry, reflecting wider investment trends in this sector. Our results may help entrepreneurs to improve their campaign disclosures and present new issues for policymakers regarding investments in digital tokens. • An integrated framework of STOs success is proposed by combining topic modelling with other campaigns' indicators. • Company's energy consumption and green impact is one of the most dealt topics among all types of projects. • The technological components in the healthcare field is a topic related to the campaign success • Energy consumption and green issues must be adequately disclosed to affect campaign success. [ABSTRACT FROM AUTHOR]

Deploying renewable energy to unit design energy-efficient technologies may fulfill the additional demand of various energy-intensive industries for their sustainability and resiliency. Multiple Stage Evaporator (MSE) is one of the most energy-intensive units used to extract the water content of the weak liquor in various industries, including the paper industry. This energy intensiveness may be reduced by integrating various Energy Reduction Schemes (ERSs). Hence, this work proposes a ERSs integrated MSE model to analyze its energy efficiency. These ERSs includes Thermo-Vapor Compressor, Steam-, Feed- Split, Feed Preheater, and Flash Tanks. Further, the performance of the proposed model is investigated under two important real-time plant complexities: Boiling Point Elevation and Fouling to achieve more realistic results. The performance analysis is initiated with the formulation of a nonlinear constrained optimization problem to increase the steam economy (SE). Also, the simulation is extended to validate at two different product concentrations (52% and 65%) by employing state-of-art optimization algorithms: CONOPT, and SCA in GAMS and MATLAB respectively. The simulated results shows an increment 1.64% and 1.37% of SE for both 52% and 65% concentration of weak liquor respectively in case of CONOPT than SCA. Also, the waste heat of the condensate, feed, and product may be further utilized for the heat recovery by incorporating the flash tanks which leads to a countable energy saving. Eventually, integrating the solar fields: PTC and LFR ensures a notable reduction in conventional heat utilization by 85.96% and 92.85%, respectively and hence, enhance the energy efficiency. • Expounded energy modeling of ERSs based MSE with BPE and Fouling. • Implementation of NLP and metaheuristic approaches for performance optimization. • Reutilization of waste heat to maximize the energy efficiency. • Integration of solar fields (PTC and LFR) to reduce conventional fuel utilization. • Prospecting the challenges and direction of energy management optimization. [ABSTRACT FROM AUTHOR]

[Display omitted] • Various carbon nanotube-based devices are developed for solar energy utilization. • The water evaporation system can generate freshwater (1.28 kg m−2h−1). • The solar-thermoelectric system can output a voltage and charge a cellphone. • The supercapacitor performs an areal specific capacitance of 19.6 mF cm−2. • The hybrid energy system can produce freshwater, generate and store electric power. Nowadays, multi-functional systems driven by solar energy have been explored to alleviate the crisis of energy and freshwater scarcity. However, it remains a great challenge to integrate multi-functions into one hybrid system with a monolithic material, which can harvest, convert and store solar energy synergistically. Here, we firstly propose a multi-functional carbon nanotube paper, which starts from a material level to solve these problems. The carbon nanotube paper is fabricated by vacuum filtration. It exhibits high efficiency of solar-thermal conversion. Secondly, three types of energy conversion/storage systems (e.g., solar-thermal evaporation system, solar-thermoelectric generation system, and supercapacitor) are constructed based on the carbon nanotube paper, which extend the research to a device level. The solar-thermal evaporation system shows an evaporation rate of 1.28 kg m-2h−1 under simulated sunlight irradiation of 1 kW m−2. The solar-thermoelectric generation system demonstrates a stable electric power generation with an output voltage of 100 mV under light irradiation of 1 kW m−2. The supercapacitors perform the energy storage function with an areal specific capacitance of 19.6 mF cm−2. These devices and systems can be used in freshwater generation (0.84 kg m-2h−1, sunlight irradiation of 1 kW m−2), water purification/desalination (inorganic ions rejection larger than 99.9%) and portable solar charging system (maximum output voltage of 5 V). Finally, a hybrid energy system is innovatively proposed from the system level to simultaneously produce freshwater, generate and store electric power. Through the synergetic coupling of solar conversion and storage technologies, the hybrid energy system can supply sustainable freshwater and electricity for remote areas in daily life, highlighting the superiority of multi-energy (thermal energy, electrical energy, and electrochemical energy) complementary. [ABSTRACT FROM AUTHOR]

Abstract The paper drying process has the highest level of energy consumption in the pulp and paper production process. Analysis and optimization of the energy system during the paper drying process is critical for improving the energy efficiency of the entire paper mill. In the existing model for the paper drying process, the solution requires accurate boundary conditions such as the air temperature and humidity of the pocket area and the cylinder surface temperature, which are very difficult to obtain in the papermaking process. This can result in significant deviations between the model solution and the actual production process. This paper focuses on the single-tier dryer cylinder-based paper drying process that has been widely used with high-speed papermaking machines in recent years. A mathematical model is proposed based on real-time data. The verification via industrial production demonstrates that the proposed model is reliable for the paper drying process. Based on the simulation results, two optimization operations have been proposed. The energy consumption decreases from 1.51 t steam/t paper to 1.44 t steam/t paper, 4.6% of the steam and 1.26 × 106 RMB can be saved for a medium-scale paper mill with the annual production capacity of 105 t paper. Highlights • Mathematical model for the single-tier cylinder based paper drying process is proposed. • Both the steam-condensate system and the paper drying process are considered. • The simulation results are verified by the industrial data from a papermaking enterprise. [ABSTRACT FROM AUTHOR]

Abstract: Based on energy flow characteristics of the paper machine drying section, the dryer section can be divided into network. The Agents applied for the proxy of energy network node. A collaboration approach based on an extended contract net protocol for dryer section energy networks of paper machine is presented, applied for Multi-level negotiation protocol to solve distribution of energy allocation and use of conflict that exist in energy used in paper machine dryer section, in which the trust degree, threshold, and priority are introduced into the classical contract net protocol. This approach resolves energy distribution conflict in the dryer section network through bidding, game theory between the central control Agents and node Agents. [Copyright &y& Elsevier]

Graphical abstract Highlights • Municipal solid waste paper was used as raw material for cellulose nanofibres (CNFs). • Pulping, washing and flotation were used as pre-treatments before nanofibrillation. • Despite different amounts of impurities in waste fibres, CNFs were obtained. • Properties of waste CNFs were affected by the used pre-treatment. Abstract When aiming for higher resource efficiency, greater utilization of waste streams is needed. In this work, waste paper separated from mixed municipal solid waste (MSW) was studied as a potential starting material for the production of cellulose nanofibres (CNFs). The waste paper was treated using three different techniques, namely pulping, flotation and washing, after which it was subjected to an ultrafine grinding process to produce CNFs. The energy consumption of the nanofibrillation and nanofibre morphology, as well as properties of the prepared nanofibers, were analysed. Despite the varying amounts of impurities in the waste fibres, all samples could be fibrillated into nanoscale fibres. The tensile strengths of the CNF networks ranged from 70 to 100 MPa, while the stiffness was ∼7 GPa; thus, their mechanical strength can be adequate for applications in which high purity is not required. The contact angles of the CNF networks varied depending on the used treatment method: the flotation-treated networks were more hydrophilic (contact angle 52.5°) and the washed networks were more hydrophobic (contact angle 72.6°). [ABSTRACT FROM AUTHOR]

• Microorganisms beneficial for effluent remediation are accounted. • Systems biology and AI tools for microbial modification are summarized. • Role of advanced oxidation processes in effluent detoxification is emphasized. • A zero waste strategy is proposed using integrated techniques. • Waste utilization and green energy production is revisited. Due to the high demand of paper and related items, pulp and paper industry is flourishing day by day. With increased production, come the hazards associated with the toxic elements present in the effluents. Various microorganisms are currently employed in the remediation of these toxic effluents. In addition, various techniques like ozonation, electrocoagulation, UV treatment, Fenton's reagent, and photo-Fenton based techniques are used in advanced oxidation processes to reduce these toxins from effluents. This review highlights various above mentioned advanced techniques and innovative processes along with the biological remediation of these toxic effluents with the help of some potential microbial consortia or their combinatory effects. Moreover, the present review will also disclose the ideas on utilizing the tools of metabolic engineering, systems biology, and artificial intelligence towards microbial engineering for relatively better bioremediation processes. In the future, these techniques might be helpful in increasing the capability of microbial consortia towards detoxification of effluents to make them environmentally safe. Finally, this review gives well-synchronized approaches to get more insights into these innovative methodologies and techniques and their use for various industrial applications. [ABSTRACT FROM AUTHOR]

Abstract: With the final aim of reducing the energy consumption and increase the methane production at Swedish pulp and paper mills, the methane potential of 62 wastewater effluents from 10 processes at seven pulp and/or paper mills (A–G) was determined in anaerobic batch digestion assays. This mapping is a first step towards an energy efficient and more sustainable utilization of the effluents by anaerobic digestion, and will be followed up by tests in lab-scale and pilot-scale reactors. Five of the mills produce kraft pulp (KP), one thermo-mechanical pulp (TMP), two chemical thermo-mechanical pulp (CTMP) and two neutral sulfite semi-chemical (NSSC) pulp. Both elementary and total chlorine free (ECF and TCF, respectively) bleaching processes were included. The effluents included material from wood rooms, cooking and oxygen delignification, bleaching (often both acid- and alkali effluents), drying and paper/board machinery as well as total effluents before and after sedimentation. The results from the screening showed a large variation in methane yields (percent of theoretical methane potential assuming 940NmL CH4 per g TOC) among the effluents. For the KP-mills, methane yields above 50% were obtained for the cooking effluents from mills D and F, paper machine wastewater from mill D, condensate streams from mills B, E and F and the composite pre-sedimentation effluent from mill D. The acidic ECF-effluents were shown to be the most toxic to the AD-flora and also seemed to have a negative effect on the yields of composite effluents downstream while three of the alkaline ECF-bleaching effluents gave positive methane yields. ECF bleaching streams gave higher methane yields when hardwood was processed. All TCF-bleaching effluents at the KP mills gave similar degradation patterns with final yields of 10–15% of the theoretical methane potential for four of the five effluents. The composite effluents from the two NSSC-processes gave methane yields of 60% of the theoretical potential. The TMP mill (A) gave the best average yield with all six effluents ranging 40–65% of the theoretical potential. The three samples from the CTMP process at mill B showed potentials around 40% while three of the six effluents at mill G (CTMP) yielded 45–50%. [Copyright &y& Elsevier]

• Caustic recovery from green liquor using electrolysis. • Feed concentration, current density, flow rate, cell geometry etc. were optimized. • Current efficiency/energy consumption were evaluated with optimized process conditions. • Results were compared between the synthetic and industrial green liquor. In the chemical recovery section of pulp and paper mills, the cooking liquor (white liquor, mainly caustic, NaOH) is regenerated by addition of fresh lime (CaO) in green liquor solution (rich in sodium carbonate, Na 2 CO 3), where calcium carbonate (CaCO 3) get precipitated leaving NaOH in solution (causticizing process). Subsequently, CaO is regenerated from precipitated CaCO 3 following washing/drying/calcination steps which are highly energy intensive and environmentally unsafe. The current investigation reports conversion of green liquor to caustic solution using electrolysis through a cation exchange membrane (CEM) placed between two electrodes. Process parameters e.g. current density, feed concentration, flow velocity, flow promoter, electrode-membrane spacing, role of gravity flow were systematically investigated to find optimum values. Process optimization was performed with Na 2 CO 3 (highest constituent of green liquor) solution to avoid complexity, which were then extended to complex salt mixtures of green liquors (synthetic/ industrial sample). Performance analysis of any batch was carried out based on moles of NaOH produced and associated current efficiency and energy consumption observed. With 600 A·m−2 current density, 1.93 mol·L−1 of NaOH could be produced in 6 h of electrolysis through a cell of 66 × 10−4 m2 of CEM, where flow rates of both feed and catholyte streams were counter current and fixed at 3.472 × 10−3 m·s−1. [ABSTRACT FROM AUTHOR]