Valorization of Wheat Straw for the Paper Industry: Pre-extraction of Reducing Sugars and Its Effect on Pulping and Papermaking Properties

Abstract

Cleaner production of sugars and pulp from renewable feedstocks has captured significant scientific attention in the recent past because they can be used for various end applications. In the papermaking industry, a major fraction of hemicellulosic sugars is lost during the pulping. The present study aims at retrieving these hemicellulosic sugars through alkali-, hot-water-, and acid-mediated extraction prior to pulping, which otherwise would have been lost during pulping and washing of pulp. These retrieved sugars can be used as feedstocks for renewable energy and value-added products. Different pretreatments were applied, aided with varying temperature, chemical concentrations, and time. Substantial amounts of total reducing sugars (TRSs) up to 21.98, 13.2, and 15.01% were extracted prior to pulping by acid, alkali, and hot-water pretreatments. Compositions of mono sugars present in the treated liquor were also characterized and confirmed by high-performance liquid chromatography analysis. The morphological changes in the wheat straw after pre-extraction were studied using the field emission gun scanning electron microscopy technique. Pulping of untreated and pretreated wheat straw was carried out at different alkali charges (12, 14, and 16% NaOH). Among all, acid-pretreated straw showed an increase in pulp yield by 10.9% at a 16% alkali charge. Physical strength properties of different pulps were further examined. Alkali- and hot-water-pretreated straw pulp retained 94.26 and 83.16% tensile indices and 92.43 and 87.02% burst indices, respectively. An increase in tear index up to 4.32, 2.01, and 2.30% for alkali-, hot-water-, and acid-pretreated straw pulp was achieved, respectively. Hot-water- and alkali-pretreated wheat straw was observed to be conducive for paper production. The integrated use of wheat straw for extraction of underutilized sugars and pulp production in this way may serve as a key stepping stone for future biorefinery designs in pulp and paper mills.

Dilute Acid Pretreatment of Wheat Stubble Agro-Residues to Eliminate Non-Process Components Meant for Papermaking and its Impact on Mechanical Strength Properties of Paper Products

“…Our finding of the improved pulping yield of acid pre-treated material is of great importance, as the previous study suggested that, acid leaching did not affect the pulping yield rather it improved delignification rate [24]. Improved pulping yield for the acid pretreated wheat stubble was also reported earlier near to 10.6% at 16% of alkali charge, which is close conformity with our finding [28]. Related to our finding of lower AA demand of acid pretreated material during pulping was suggested and it could be due to a decline in the extractive content [13].…”

“…3. Even though the earlier report confirmed the enhanced lignin content of wheat straw up to 25.67% due to pretreated with 0.1N H 2 SO 4 at 125̊C for 120 minutes [28]. While in the case of extractive removal, acid pretreatment caused its removal to a greater extent at higher pH and high retention time, it means increased pH (1.5-2.5) and increased retention time (0.5-1.5 hr) resulted in higher removal of extractive from 24.8 to 50% and from 26.9 to 65.4 % respectively, while increased consistency resulted in decreased extractives removal as shown in Fig.…”

“…The measurement of stretch or elongation of paper before its break was found to be about 3.03% and 3.12% for kraft pulp of untreated and treated samples respectively, whereas in the case of soda pulp it was 2.81 and 2.88% respectively for untreated and treated samples, thus acid pretreatment of fibrous raw material developed the fibre with more modulus of elasticity. Paper with increased tear index from 5.0 to 5.3 mN.m 2 /g and 4.5 to 4.9 mN.m 2 /g was identified for kraft and soda respectively when the raw material was pretreated with acid, an increased tear index of paper from 6.94 mN.m 2 /g to 7.1 mN.m 2 /g was investigated earlier due to acid pretreatment of wheat stubble, which was pulped at 16% active alkali [28].…”

Biodegradation of Straw Lignin by Culture of the Fungus Schizophyllum Commune Isolated From the Tree Surface

“…Соотношение вышеуказанных групп зависит от источника лигнина [7]. Сухая масса клеточной стенки на 20-35% состоит из лигнина, в зависимости от растения, мягкая древесинана 25-35%, а лиственная древесинана 20-25% [8].…”

An analysis of China's biomass briquette fuel large‐scale steam heating system

“…2 Compared with conventional energy, crop straw is a renewable resource that can be completely degraded by composting over a short period. Crop straw contains cellulose, hemicellulose and lignin that can be used for ethanol production, 5,6 feed production, 7,8 paper making, 9,10 agricultural fertilizers, 11,12 edible fungi cultivation, 13,14 etc. The efficient use of crop straw can save the consumption of traditional energy, such as crude oil and natural gas.…”