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Mitigation of global warming, energy security and industrial competitiveness urge the energy-intensive pulp and paper industry (PPI) to transform energy use practices. This study investigates how the PPI has responded to the need for the energy transition in the 2000s. Finland and Sweden as forerunners of energy-efficient operation and decarbonization of the PPI are used as target countries. Understanding of changes in energy consumption is complemented using decomposition analysis (Logarithmic Mean Divisia Index Method) and the energy efficiency index approach. Analysis of companies’ investments in energy technologies is used for explaining changes in energy production. Evidence of significant development towards the more sustainable operation of the PPI was found. Energy consumption per produced unit has decreased, i.e., energy efficiency has improved. Fossil fuels have been partially replaced with bio-based alternatives. Thus, the CO2 intensity has decreased substantially. The generation of renewable electricity has increased in both countries. Examples of Finland and Sweden indicate that the PPI has great potential to contribute to CO2 emission reduction worldwide in the future as energy efficiency can be further improved, and the share of fossil fuels can be decreased increasing the use of biofuels and self-generated green electricity at least in kraft pulp mills.

Transition towards carbon neutrality will require application of negative carbon emission technologies (NETs). This creates a new opportunity for the industry in the near future. The pulp and paper industry already utilizes vast amounts of biomass and produces large amounts of biogenic carbon dioxide. The industry is well poised for the use of bioenergy with carbon capture and storage (BECCS), which is considered as one of the key NETs. If the captured carbon dioxide can be used to manufacture green fuels to replace fossil ones, then this will generate a huge additional market where pulp and paper mills are on the front line. The objective of this study is to evaluate future trends and policies affecting the pulp and paper industry and to describe how a carbon neutral or carbon negative pulp and paper production process can be viable. Such policies include, as examples, price of carbon dioxide allowances or support for green fuel production and BECCS implementation. It is known that profitability differs depending on mill type, performance, energy efficiency, or carbon dioxide intensity. The results give fresh understanding on the potential for investing in negative emission technologies. Carbon capture or green fuel production can be economical with an emission trade system, depending on electricity price, green fuel price, negative emission credit, and a mill’s emission profile. However, feasibility does not seem to evidently correlate with the performance, technical age, or the measured efficiency of the mill.

Polysulfide pulping is a method to increase the pulp yield in a kraft pulp mill. Higher production is in the core of pulp mill process development, but modifications in cooking raise questions on their effects on the other parts of the process. This study focuses on the impacts of polysulfide pulping on the energy use and production of kraft pulp mills. The impacts are estimated by calculating and analyzing the steam and electricity balances of reference softwood and hardwood mills. Energy generation using residual biomass is an essential part of the operation of a kraft pulp mill, and often a notable source of income. The results show that implementation of polysulfide cooking affects both energy consumption and production. Higher hemicelluloses content of pulp cooked using polysulfide liquor means that less organic material ends up in the black liquor. Subsequently, the recovery boiler energy production suffers. The reduced steam production together with increased steam consumption decreased electricity production, corresponding to a decline in sellable electricity of 22.4 % in the hardwood mill and 28.4 % in the softwood mill. The study shows that increasing the pulp production by investing in polysulfide cooking in stand-alone kraft pulp mills can be economically feasible.

A modern pulp mill generates a variety of different by-products and waste streams, some of these can be recycled, refined, sold, or used on-site for energy production. However, some, such as chemical and biological sludges produced in wastewater treatment cannot be reused or disposed of easily, mainly due to their high moisture content and poor drying characteristics. Tightening legislation regarding waste disposal as well as the growing need to increase the process efficiencies of pulp mills act as driving forces to find environmentally friendly and energy-efficient techniques for pulp mill sludge treatment. This study summarizes the current methods for pulp mill sludge handling and evaluates the potential of hydrothermal carbonization (HTC), a conversion process through which wet organic substrates can be transformed into a carbonaceous material (hydrochar). Depending on the process parameters, the material’s structure is modified, enabling hydrochar use in energy, soil conditioning and adsorption applications. The sludges were hydrothermally carbonized at 180, 200, 220 and 240 °C for 3 h. The hydrochar and liquid products’ main properties were analyzed. Their potential applications were also evaluated. The effective treatment of sludges from the pulp industry with HTC could transform energy-demanding waste into a value-added source of materials.

This work describes and discusses sources of noncondensible gases (NCG) in modern kraft pulp mills and modern NCG collection from process units where odor emissions can occur if these gases are released to the surroundings. A mill-wide overview of NCG sources and collection in modern pulp mills is provided. Using modern practices, malodorous gases can be collected to the extent that a pulp mill is essentially odor free. The key to limiting complaint-causing odors is prevention of these emissions during process disturbances, equipment malfunctions, operator errors, and other unforeseen occurrences.

In this work, the production viability, physical, chemical and mechanical properties of briquettes produced from mixtures of coffee shrub residues and pinewood, were evaluated. The densification was carried out under constant operating conditions (temperature of 120 °C, pressure of 8.27 MPa) in a piston-press type laboratory-scale briquetting machine. Coffee shrub residues were mixed with pinewood in ratios of 25%, 50% and 75%. In addition, reference briquettes of pure pinewood and of each type of coffee shrub residue were produced. To characterize the raw material, ash content, volatile matter, fixed carbon together with the calorific value of produced samples, were measured. To characterize the suitability of the briquettes produced: apparent density, energy density, tensile strength, and equilibrium moisture content were determined. The highest values of energy density (19133–19899 MJ m−3), tensile strength (415–569 kgf), apparent density (1107–1163 kg m−3) and favorable values of equilibrium moisture content (9–11 wt %) were obtained from a mixing ratio of 75% of pinewood. The novel contribution of this research was to develop briquettes with appropriate physical and mechanical parameters from new raw materials that could serve as sustainable fuel sources for local firing systems.

Chemical quantitative characterization of biomass is relevant for waste to energy recovery technologies. In the present work, selected agroindustry solid residues from coffee crops – parchment and coffee shrub, i.e., stem, branches and leaves – were characterized. Properties such proximate, ultimate and biochemical composition, energy content, and thermogravimetric analysis, were evaluated. Results showed high values of higher heating value and volatile matter content. The silica contents are small for all samples. Additionally, the high content of extractives and lignin, reveal that these residual biomasses are more suitable for charcoal than cellulose pulp production. The extensive residue characterization provided valuable data that helped in outcome of the evaluation of different conversion technologies as being an environmentally friendly alternative, contributing to sustainable, reliable, carbon-neutral form of modern energy and upgrade the large quantity of waste generated by the coffee industry into energetically valued residues, by improving their management.

Upgrading biomass waste streams can improve economics in wood industries by adding value to the process. This work considers use of a hydrothermal carbonization (HTC) process for the residual feedstock after lignin and hemicelluloses extraction. Batch experiments were performed at 200&ndash, 240 &deg, C temperatures and three hours residence time with an 8:1 biomass to water ratio for two feedstocks: Raw spruce and spruce after lignin extraction. The proximate analysis and heating value showed similar results for both feedstocks, indicating that the thermochemical conversion is not impacted by the removal of lignin and hemicelluloses, the pretreatment processing slightly increases the heating value of the treated feedstock, but the HTC conversion process produces a consistent upgrading trend for both the treated and untreated feedstocks. The energy yield was 9.7 percentage points higher for the treated wood on average across the range temperatures due to the higher mass yield in the treated experiments. The energy densification ratio and the mass yield were strongly correlated with reaction temperature, while the energy yield was not. Lignocellulosic composition of the solid HTC product is mainly affected by HTC treatment, the effect of lignin extraction is negligible.

Torrefied biomass has considerable potential as a biomass fuel to replace coal in energy and process heat production. The aim of this paper is to evaluate the potential of torrefied biomass in different industries, both power and non-power generation industries, and considers the impact of such use on the international biomass market. The power generation sector has been so far the leader in testing torrefied biomass use with other industrial demand lagging behind. There are promising technical possibilities for greater torrefied biomass use in a number of other areas such as the steel, non-metallic minerals, as well as the pulp and paper industries. Although a large increase in torrefied biomass consumption by industry is not immediately foreseeable, industrial use by actors outside the energy generation sector could increase demand for torrefied biomass in general and, as a result, stimulate development of global torrefied biomass markets. Results show that the torrefied biomass demand significantly depends on the bioenergy markets. It seems that despite of the challenges, the growth of torrefied biomass demand will have a large progress in coming years. Post-print / final draft

Biomass conversion via thermal processes to generate energy will be an important part of the future energy landscape. The objective of this study was to determine the kinetic parameters of five types of eucalyptus wood derived from different clones, sugarcane bagasse, elephant grass, bamboo and fibers of coconut fruit. The framework to describe the kinetic pyrolysis consists of a fuel model including four constituents, namely hemicelluloses, cellulose, lignin and extractives. Each pseudo-component was converted via two competing reactions into volatile and char. A statistical fit was achieved with mass loss rate data, obtained from the pyrolysis modeling and the thermogravimetric analysis, providing satisfactory statistical variance. In the end of the kinetic parameters optimization, the activation energies for reaction of hemicelluloses, cellulose and lignin were obtained as 179.98, 130.0 and 40 kJ mol−1, respectively, whereas the decomposition of the pseudo-components resulted in relatively similar values of pre-exponential factor for all biomasses evaluated. The experimental results and kinetic parameters provide useful data to improve design of thermochemical conversion units.

Corporate image, European Emission Trading System and Environmental Regulations, encourage pulp industry to reduce carbon dioxide (CO2) emissions. Kraft pulp mills produce CO2 mainly in combustion processes. The largest sources are the recovery boiler, the biomass boiler, and the lime kiln. Due to utilizing mostly biomass-based fuels, the CO2 is largely biogenic. Capture and storage of CO2 (CCS) could offer pulp and paper industry the possibility to act as site for negative CO2 emissions. In addition, captured biogenic CO2 can be used as a raw material for bioproducts. Possibilities for CO2 utilization include tall oil manufacturing, lignin extraction, and production of precipitated calcium carbonate (PCC), depending on local conditions and mill-specific details. In this study, total biomass-based CO2 capture and storage potential (BECCS) and potential to implement capture and utilization of biomass-based CO2 (BECCU) in kraft pulp mills were estimated by analyzing the impacts of the processes on the operation of two modern reference mills, a Nordic softwood kraft pulp mill with integrated paper production and a Southern eucalyptus kraft pulp mill. CO2 capture is energy-intensive, and thus the effects on the energy balances of the mills were estimated. When papermaking is integrated in the mill operations, energy adequacy can be a limiting factor for carbon capture implementation. Global carbon capture potential was estimated based on pulp production data. Kraft pulp mills have notable CO2 capture potential, while the on-site utilization potential using currently available technologies is lower. The future of these processes depends on technology development, desire to reuse CO2, and prospective changes in legislation. Publishers version

To increase the understanding of hydrothermal carbonization (HTC) of lignocellulosic biomass residues, four feedstocks: giant bamboo, coffee wood, eucalyptus, and coffee parchment, were studied. The effect of operating conditions on the products in terms of yield, composition and energy densification were quantified. Each feedstock was treated for 3 h at temperatures of 180, 200, 220 and 240 °C. For all samples, the higher heating value (HHV), fixed carbon content and energy density increased with increasing reaction severity, while volatile matter content and mass yield decreased. The HHV of hydrochar samples obtained at temperatures ≥220 °C were in the range of 24.6–29.2 MJ kg−1 and indicated the high potential of these materials for fuel applications. The mass yields varied in the range of 46.5–56.9%, with the exception for coffee parchment, where the lower values of 34.4–46.0% were obtained. The fixed carbon varied from 33.8% to 53.0%. The HTC liquor had pH values of 2.9–4.4 due to organic acids. The results were used to model and evaluate different industrial-scale HTC simulation cases. The overall efficiency was similar within all studied biomasses. The integration with a bio-fired power plant allows simplification of the process while also bringing efficiency gains. All studied biomasses appear to be suitable for energy and value-added products generation through HTC treatment. Coffee residues, which have received little research consideration previously, responded well.

Coffee production in Brazil creates significant amounts of residues. The goals of this study are to evaluate the characteristics of these residues (parchment, husk, pulp, spent grounds, silverskin and defective beans); to discuss their potential for conversion to improved biofuels via thermochemical methods; and to develop mass and energy balances of the processes to help determine the value of residues for direct combustion, fast and slow pyrolysis, gasification, hydrothermal carbonization and torrefaction. Particularly the pulp, but also husk and parchment, are characterized by high moisture, as well as high contents of cellulose (41–64%) and hemicellulose (27–35%). These residues are suitable for several conversion routes, albeit with the drawback of drying need for the dry methods. The ash of these also creates a risk of fouling, corrosion and agglomeration with high-temperature and fluidized bed technologies. The silverskin and some of the defective beans are available at lower moisture. The spent coffee grounds appear a particularly advantageous residue for energy use: while moisture varies, the roasted product dries easily and has the highest heating value of the residues. For defective beans, little thermochemical treatment data is available. Among the technologies, for wet feedstocks hydrothermal carbonization has the advantage of post-conversion drying. Gasification appears advantageous for parchment with a high syngas yield and heating value. Fast pyrolysis of biomass suffers from the oxygen content of the liquid, requiring additional treatment; slow pyrolysis may be more appropriate. In conclusion, coffee residues have potential as feedstocks for a number of thermochemical conversion processes.

Pulp mills are making increasing efforts to reduce fossil fuel use and carbon dioxide emissions. Lime kilns, which are typically fired with fuel oil or natural gas, use the most fossil fuel in modern pulp mills. A modern kraft pulp mill can be fossil fuel-free during normal operation if fossil-based lime kiln fuels are substituted with renewable alternatives. This study compared the production and use of various renewable fuels, namely, hydrogen, producer gas, torrefied biomass, lignin, and pulverized biomass, in lime kiln operations in a 1.5 Mt/a kraft pulp mill in South America to define the techno-economic optimum for the fossil fuel-free operation of the pulp mill. The attractiveness of each of the concepts was dependent on local conditions and especially the prices of fossil fuels and electricity. The results showed, however, that feasible options exist for the replacement of fossil fuels in lime kiln operations.

A key challenge in prevention of global warming is how to increase energy efficiency, to be able to deal with increased fossil CO2 emissions from rising energy usage. Increasing energy efficiency will decrease energy usage and is in a key role in emission mitigation. The focus is the pulp and paper industry, which is energy-intensive. Development of industrial energy efficiency has been studied before but the role of industrial transformation is still mostly unknown. The knowledge must be improved, to be able to predict future developments in the most effective way. In this research, impact of various production unit closures and start-ups on energy efficiency of the Finnish pulp and paper industry were studied utilizing statistical analysis. Results indicate that about 20% of the Finnish pulp and paper industry energy efficiency improvement between 2011 and 2017 is caused by the major structural changes. The rest, 80% of the progress, was mainly due to improved technology and more optimal operational modes. Additional findings suggest that modern mill start-ups have a significantly greater potential to reduce energy consumption than old mill closures.

The implementation of wood extraction prior to pulping (pre-hydrolysis), with subsequent recovery of hemicellulose, is expected to affect the operation of a conventional kraft pulp mill. The magnitude of impacts will depend especially on the extraction conditions. In this specific work, the consequences of integrating the auto-hydrolysis process are studied using a detailed mill balance. A softwood pulp mill in Finland was used as a reference. With 14.1% of wood extracted, the wood demand increased by 15.5% and the steam generation in the recovery boiler by 13.5%. The removal of approximately 17% of lignin from black liquor would put the flue gas side of the boiler back to the original required capacity. In turn, this would enable the simultaneous recovery of lignin and hemicellulose. To make this process economically feasible, the extra revenue from the sales of lignin and hemicellulose products would need to compensate for the additional operating costs in the pulp mill.

Aim of the study was to investigate how hydrothermal carbonization changes adsorption efficiency toward metal ions of typical sludges. Hydrothermal carbonization is a novel and green method of treating biomasses. Reactions take place in an aqueous environment at relatively mild temperature and high pressure resulting a different end biomass structure than obtained from traditional pyrolysis. Anaerobically digested sludge (ADS) and pulp and paper industry sludge (INS) were utilized as a feedstock. Adsorption behavior of ADS and INS was examined towards Pb(II), Cr(III), Cr(VI), As(III) and As(V). Both ADS and INS were found to remove Pb(II) effectively and followed Sips adsorption isotherm. Adsorption kinetics was fast and followed pseudo-second order model. Furthermore, intraparticle diffusion was observed to be partly responsible in the adsorption process. Hydrothermal carbonization indicated high potential for the production of novel carbonaceous materials for metal removal from waters.

Industrial energy efficiency has received increasing attention in many countries because of its importance in the pursuit of energy supply security, increased economic competitiveness and in the mitigation of greenhouse gases emissions. This paper aimed to evaluate the energy consumption development of the Brazilian pulp and paper industry through an energy decomposition analysis and an energy efficiency index approach over a 30 years period. An international comparison with other important paper-producing countries ( i.e. , Canada, United States of America, Finland and Sweden) was carried out. It was concluded that despite a significant increase in the energy efficiency levels, responsible for 5.6 PJ savings in electricity consumption and for 38.6 PJ savings in fuels consumption between 1979 and 2009, a saving potential of 7.8 PJ and 146.2 PJ related to the annual consumption of electricity and fuels, respectively, could be identified in the Brazilian pulp and paper industry. Among the countries evolved in the international comparison, both the Swedish and Finnish industries were the most efficient, followed by the Brazilian, American and Canadian, the latter being the only one where there was a reduction in the energy efficiency levels from 1979 to 2009.

The main objective of this study is to evaluate the effect of chlorine (Cl) and potassium (K) on the operation and design of equipment in the chemical recovery cycle. Due to stricter environmental regulations, mill closure tends to increase, causing the accumulation of undesirable elements such as Cl and K in the kraft liquor cycle. Total inorganic solids in pulping liquors increase in the presence of Cl and K, which affects the operation of chemical recovery equipment. The objective here is to show the magnitude of these impacts and estimate operational cost differences by using different Cl and K contents in liquors. Pulp mill material and energy balances for each case are used for this purpose, and a modern Brazilian pulp mill served as a base case model. The results show that for one specific range, the solids content in black liquor can be 6.6% higher by increasing the mass percentage of Cl and K in black liquor. This difference reduces the black liquor higher heating value by 6.2% and increases the amount of dry solids to burn in the recovery boiler, also by 6.6%. The evaporation load increases along with steam consumption. This lowers total electricity output by up to 1.6 MW due to reduced flow to the condensing stage of the steam turbine. The balances also demonstrate that some pumping costs can be 12% higher when operating from a low to high concentration of Cl and K in black liquor.

Hydrothermal carbonization of biomass presents a promising way to improve fuel characteristics of biomass without preliminary drying. In this process, feedstock is subjected to heating with water at temperatures between 180 and 250 °C during a certain period of time. This paper investigates the effect of process conditions (temperature, time, and the ratio between biomass and water) on the hydrothermal carbonization of coniferous biomass. Three sets of experiments were carried out with coniferous wood chips. Mass and energy yields together with proximate analysis measurements were used for the carbonization process evaluation. Dependencies of hydrochar mass and energy yields from the operation parameters could be described with mathematical correlations. Post-print / Final draft

Pulp and paper companies are seeking opportunities beyond the traditional production of market pulp. One interesting alternative is to expand their revenue streams by adding value to the wood residues that they generate. Considering that excess heat and electricity can be used for biomass pre-treatment and conversion, the aim of this work is to show how the integrated production of bio-oil or biochar would affect the operation of a 1.5M t/a kraft pulp mill in South America. Detailed balances with a focus on modern eucalyptus mills are then developed for this purpose. Since the attractiveness of increasing renewable energy is often influenced by energy policies or local market development for the new products, the target was not to determine the best investment decision. Nevertheless, an economic analysis was performed to observe the main variables affecting the viability of these technologies. The results showed that satisfactory internal rates of return can be achieved for multiple technologies depending on the price of electricity, torrefied pellets, or bio-oil.