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Modern NCG practice, TAPPI Journal July 2026

ABSTRACT: New innovations have been put in operation for collection and handling systems of noncondensable gases (NCGs) in modern kraft pulp mills. This work investigates technologies in new pulp mills that aim to achieve the benefits of odor-free processes while enhancing chemical circulation within the mill. It describes and discusses both past and current systems for collecting and handling NCGs. The mills studied have designed and implemented their NCG systems within the past 10 to 15 years. New innovations have emerged, offering promising methods to further reduce occasional sulfurous odor emissions from the kraft process. These methods explore pretreatment and sulfuric gas stream reuse options in process units where these gases are generated or during the transportation of these side streams to their final destruction site. Using modern practices outlined in this paper, malodorous gases can be collected to the extent that a kraft pulp mill is essentially odor-free pending operator errors or major equipment malfunctions. One of the difficult aspects is that NCG systems in kraft mills are often designed case-by-case, as well as by various equipment vendors and with varying numbers of destruction sites. The actual detailed design depends on the chosen layout, process configuration depending on individual equipment purchased, and even on the design practices of individual suppliers.

Effects of calcium on sodium salt scaling with the presence of resin acids and fatty acids, TAPPI Journal June 2026

ABSTRACT: Reintroducing tall oil soap or its related products into high dry solids black liquor has been found to reduce sodium salt scaling in falling film evaporators. Aside from resin acids and fatty acids, which are the likely scale inhibitors, calcium is reintroduced into black liquor because of the relatively high calcium content of tall oil soap. One concern is that this increase in calcium content might lead to the formation of additional calcium and sodium scales in evaporators. In this work, we investigated the relationship among trace amounts of calcium, sodium salts, resin acids, and fatty acids in a controlled system using a model salt solution and a benchtop setup. We studied the effects of the calcium carbonate addition and calcium carbonate scales on sodium salt scaling in the presence of resin acids and fatty acids. We found that some calcium carbonate is incorporated in the precipitated sodium crystals, and the suspended sodium crystals become larger and more compact with increasing calcium carbonate concentration. Experiments in the benchtop setup show that precipitating calcium carbonate scale on the heat exchanger does not lead to a higher rate of sodium salt scaling. The solubility of calcium carbonate is not affected by the addition of resin acids and fatty acids. These findings indicate that the reduction in sodium salt scaling through the addition of tall oil soap is primarily related to resin acids and fatty acids, rather than to calcium or to interactions between calcium and mixtures of resin and fatty acids.

Optimization of optical coverage of board surfaces with assessment of light scattering and absorption using mineral as a coating component, TAPPI Journal June 2026

ABSTRACT: One of the primary functions of mineral inclusion into paper or paperboard is to improve the optical performance of the substrate. A coating may be applied to a sheet in order to cover a dark base, to improve the sheet opacity, to give the correct smoothness and gloss, or to give a suitable surface on which to print. The brightness of a pigment has long been used as a guide for pigment choice in paper and board. However, the measured paper brightness is a function of color and light absorption (K) of the coating and base and the light scattering (S) within the sheet resulting from interfaces with different refractive index. The optical performance can be quantified by measuring the S&K coefficients as described by the Kubelka-Munk model/theory in a filled or coated paper sheet. In coating, this is often assessed as a function of coat weight, and the corresponding physical sheet properties are assessed at the same time; for example, the correct gloss, smoothness, point-to-point uniformity, and printability. The optical performance in the sheet is often not directly related to the pigment brightness, but is largely a function of the particle packing within the sheet and coating layer. In the first and second main sections of this work, respectively, we show how S&K calculations from the Kubelka- Munk equations can be used in coated sheets to determine the optical performance and how this can be used as a predictive tool for the final sheet performance. This is presented for base sheets with different starting brightness. The third section of this work focuses on how mineral combinations in coatings can be used to improve the light scattering and consequently the optical performance of the board. We include theoretical considerations and then finally share a case study for improvement on the optical properties of recycled board.

Preparation of a vegan leather from mycelium with papermaking method, TAPPI Journal June 2026

ABSTRACT: With growing concern over the environmental impacts of both natural leather and conventional synthetic leathers, the development of sustainable and eco-friendly leather alternatives has become an urgent research priority. In this study, an innovative wet papermaking strategy is proposed to fabricate continuous, homogeneous mycelial sheets from chitin-rich fungal mycelium, mimicking the matrix structure of genuine leather. These mycelial sheets were chemically modified to meet the performance requirements of leather foam layers. Subsequently, the modified mycelial sheets were combined with a substrate fabric to produce a novel mycelium-based leather composite (myco-paper leather) that achieves an excellent balance of mechanical properties and tactile qualities. Experimental results demonstrate that the mycelium-sheet-based leather substitute exhibits remarkable mechanical performance, with a tensile strength of approximately 45 MPa and an elongation at break of about 10.5%. After lamination with the substrate fabric, the composite material shows a tear strength of approximately 16 N, along with a desirable hand feel and surface texture. Following tannic acid tanning, the mycelial sheets also exhibit significant antimicrobial and antifungal properties, forming an inhibition zone of approximately 2 mm against Staphylococcus aureus. Through reinforcement with plant fibers, the developed material attains both strength and flexibility, indicating that the wet papermaking of mycelial sheets is a feasible and scalable approach for producing sustainable leather alternatives. This work not only employs a simple and mature papermaking process to process fungal mycelium but also provides a new conceptual and practical foundation for the large-scale production of bio-based leather substitutes. The findings have significant implications for advancing a low-carbon, sustainable leather industry.

Investigation of the factors contributing to malodorous gases emission during secondary fiber reuse, TAPPI Journal June 2026

ABSTRACT: Malodorous gases are commonly produced during secondary fiber reuse, which is harmful to human health and causes environmental pollution. This paper investigated the influence of fiber type and concentration, temperature, and whitewater concentration on the malodorous gases. The results indicated that, in pulp prepared with fresh water, bleached hardwood kraft pulp (LBKP) did not produce malodorous gases after standing for five days. In contrast, the secondary fiber began to release substantial amounts of total volatile organic compounds (TVOC) on the third day and hydrogen sulfide (H2S) and ammonia (NH3) on the sixth day, and black substances began to appear in the pulp, which proved that the microorganisms began to proliferate. With the increase of the secondary fiber concentration, the release amounts of TVOC, H2S, and NH3 gradually rose, along with the black substances in the pulp. With increased temperature, the release of TVOC increased steadily, while the release of H2S and NH3 reached the maximum at about 45°C, and then began to decline. The decrease of the pulp freeness accelerated the generation of the malodorous gases, but the total release amounts of TVOC, H2S, and NH3 were basically the same. With the increase of white water concentration, the release of TVOC, H2S, and NH3 increased rapidly. When the white water/fresh water was 20 mL/80 mL, the slurry changed from pale yellow to aterrimus on the sixth day. Therefore, microorganisms in the secondary fiber caused pulp deterioration, while white water was the main reason for generating a large amount of malodorous gases.

Textiles: A New Door of Opportunity Opens, Paper360º November/December 2022

Utilization of palm fiber as papermaking materials: Microscopic structure and chemical pulping, TAPPI Journal October 2022

ABSTRACT: The microscopic structure and pulping properties of palm fiber were explored. Soda cooking and sulfate cooking were conducted and compared in terms of physical strength of the obtained pulps. Sulfate pulp showed better performance than soda pulp, as indicated by the 23% higher tensile index, 49% higher tear index, and 36% higher burst index. To further elevate physical strength, long fibered pulp (LFP), namely commercial softwood sulfate pulp, was mixed with sulfate pulp of palm fiber at levels from 20% to 50%. At the blend level of 50%, tensile index of 52.13 Nœm/g, tear index of 15.63 mNœm2/g, and burst index of 3.42 kPaœm2/g were attained. The lignin in spent liquor from pulping was isolated and characterized. Soda lignin of palm fiber was mainly composed of guaiacyl and syringyl units, and showed weight-average molecular weight of 3616 g/mol.

A true green cover for industrial waste landfills, TAPPI Journal April 2024

ABSTRACT: Greenhouse gas (GHG) emissions in the United States totaled 5,981 million metric tons of carbon dioxide equivalent (MMT CO2eq) in 2020. Of that, GHG emissions by the pulp and paper sector amounted to 35 MMT CO2eq direct emissions and those by industrial waste landfills summed to 7.4 MMT CO2eq direct emissions. Loss of GHG sinks due to change in land use further contributes to the net GHG emissions. Industrial waste landfills are typically required to comply with certain federal and state regulations, including meeting requirements for final cover systems. Conventional final cover systems have included use of soil covers and/or soil-geosynthetic composite covers. An engineered turf cover provides for an excellent “green” alternative final cover system for industrial waste landfills.This paper discusses various sustainability aspects pertaining to use of an engineered turf final cover, including: (i)significantly low carbon footprint associated with the construction of an engineered turf alternative final coverwhen compared to closure using a traditional or prescriptive cover system; (ii) saving valuable soil and land resourc-es; (iii) saving water resources by reduction in its use during and after construction; (iv) reducing impacts associated with borrow areas; and (v) reducing overall carbon footprint. Further, when using an engineered turf cover, opportunities exist for beneficial reuse of land, including development of solar energy. A brief discussion on the potential fordevelopment of solar energy is included.

Sulfur makeup in an unbleached kraft pulp mill, TAPPI Journal August 2024

ABSTRACT: Sodium sesquisulfate or “sesqui” (Na3H(SO4)2) is a by-product of chlorine dioxide production at kraft pulp mills. It is typically used for sodium and sulfur makeup in the liquor loop. Mondi Hinton Inc. (MHI) in Hinton, AB, Canada, was converting from bleached to unbleached kraft pulp production and was thus losing this source of makeup. The only option that was readily available as a substitute was sodium hydrosulfide (NaHS), which was cost prohibitive. Other options such as sodium sulfate (Na2SO4), emulsified sulfur, sulfuric acid (H2SO4), and sodium bisulfite (NaHSO3) were compared. The mill concluded that pelletized sulfur plus sodium hydroxide or “caustic soda” (NaOH) was the best option. Laboratory-scale experiments showed that pelletized sulfur dissolved in white liquor (WL). A mill-scale trial revealed that pelletized sulfur added to a causticizer had no adverse impacts on the downstream pressure filters or kiln operation. The sulfur reacted to produce polysulfide upstream of the WL storage tank, giving the liquor an orange hue. This polysulfide appeared to partially degrade into thiosulfate before being fed to the digester. The heavy black liquor (HBL) sulfur:sodium (S:Na) ratio did not change significantly, even though the sulfur/soda addition location was upstream of the original one. In addition, other properties such as liquor heating value and elemental analysis did not significantly change. Due to polysulfide/thiosulfate concentration in the white liquor, it was determined that the carbon steel equipment was at risk for corrosion. During the annual turnaround that occurred eight months after the addition of sulfur was started, the wash zone of the digester showed no signs of thinning/damage. The mill has been running exclusively with pelletized sulfur for 22 months (as of August 2024), realizing significant cost savings compared to the use of NaHS or other sulfur/soda addition options.

The role of hornification in the deterioration mechanism of physical properties of unrefined eucalyptus fibers during paper recycling, TAPPI Journal February 2024

ABSTRACT: Physical properties of cellulosic paper deteriorate significantly during paper recycling, which hinders the sustainable development of the paper industry. This work investigates the property deterioration mechanism and the role of hornification in the recycling process of unrefined eucalyptus fibers. The results showed that during the recycling process, the hornification gradually deepened, the fiber width gradually decreased, and the physical properties of the paper also gradually decreased. After five cycles of reuse, the relative bonding area decreased by 17.6%, while the relative bonding force decreased by 1.8%. Further results indicated that the physical property deterioration of the paper was closely related to the decrease of fiber bonding area. The fiber bonding area decreased linearly with the reduction of re-swollen fiber width during paper recycling. Re-swollen fiber width was closely related to the hornification. Hornification mainly reduces the bonding area of unrefined eucalyptus fiber rather than the bonding force. The work elucidates the role of hornification in the recycling process of unrefined eucalyptus fibers and the deterioration mechanism of paper physical properties, which will be helpful to control the property deterioration of paper and achieve a longer life cycle.