Bioenzymes Power the Paper Industry’s Green Shift: Lower Energy, Less Pollution

China’s pursuit of its “dual carbon” goals is making energy conservation and emissions reduction increasingly urgent in textiles, papermaking, pharmaceuticals and other priority sectors. Biotechnology is expected to act as an accelerator, helping these industries move faster toward greener operations. Against this backdrop, this publication launches the “Green Biomanufacturing” series, examining how biotech can help traditional industries escape high energy consumption and high pollution.

Comparing today’s paper with earlier products reveals a clear trend: paper quality has kept improving, and whiteness has risen as well.

Yet behind that clean, refined appearance, the paper industry still carries a heavy burden of high pollution and high energy consumption.

At the same time, China has a large population but limited forests, and wood pulp is in short supply, leaving the paper sector long dependent on imported virgin pulp and recovered paper. Under a joint announcement by the Ministry of Ecology and Environment and other departments, China had basically achieved zero imports of solid waste by the end of 2020, making imported waste paper an unviable route for papermaking.

In recent years, tightening environmental rules and cost pressure have combined to reshape the industry’s raw material mix. Non-wood materials such as straw, together with high-yield mechanical pulp processed with bioenzyme assistance, are quietly altering papermaking’s feedstock structure and opening new possibilities, especially for packaging paper.

The Pain Points Beneath Paper

Papermaking is one of China’s four great inventions and has had far-reaching influence. China’s paper industry has long ranked first worldwide in both output and sales, accounting for roughly one quarter of the global total.

As internet technology spreads, electronic reading has become commonplace. In the short term, however, paper remains indispensable in many areas, including textbooks, advertising printing and household paper.

No matter the paper grade, it all begins with wood fiber. Professor Dai Hongqi of Nanjing Forestry University explains that plant materials must first be chipped or cut short; then alkaline high-temperature cooking or mechanical grinding separates the fibers into pulp. After mechanical refining, the pulp is dewatered on a paper machine at a certain consistency to form a wet web, which is further dewatered by pressing and finally dried into paper.

To obtain the wood fiber needed for pulping, large amounts of water, electricity and alkali must be consumed, while substantial volumes of dark, foul-smelling and toxic wastewater are generated. As a result, many paper companies have repeatedly appeared on environmental blacklists.

Although China is vast and resource-rich overall, its forest resources are relatively scarce, with per capita forest area only one seventh of the world average. To reduce domestic timber consumption and ease the environmental pressure from wastewater discharge, China has imported large volumes of wood pulp and waste paper in recent years to support national economic development.

Dai notes that imported wood pulp can be used directly for papermaking, including ivory board, household paper and specialty paper, while imported waste paper is mainly used for board, packaging paper and newsprint—such as the boxes, corrugated board and kraft paper widely used in e-commerce delivery.

At present, imported pulp accounts for as much as 40% of China’s papermaking pulp. To ease fiber shortages and lower production costs, papermakers are turning to more cost-effective non-wood raw materials.

Dai told Science and Technology Daily that pulping raw materials fall into wood and non-wood categories. Besides forest timber, straw, bamboo, reed, miscanthus and cotton stalk are all non-wood materials. In the past, technical and process limits meant chemical pulping from non-wood materials had low black liquor extraction and alkali recovery rates. Pulp was bleached with elemental chlorine, producing wastewater that was hard to treat and extremely high in adsorbable organic halides (AOX), causing severe ecological damage and posing risks to human health.

As China’s economy grew rapidly and environmental protection and pollution control intensified, nearly all non-wood fiber pulping and papermaking operations were shut down after 1990. To date, only a small number of bamboo pulp papermakers in regions such as Sichuan remain in operation.

New Opportunities for Non-Wood Fiber Pulping

Although non-wood pulping was once completely prohibited, research into non-wood fiber utilization did not stop. In recent years, biomass refining and high-yield chemi-mechanical pulping have become hot topics, drawing industry attention and bringing non-wood pulp back onto the papermaking stage.

Dai told reporters that biorefining can turn different components of non-wood fiber materials into separate resources, especially enabling high-value use of hemicellulose and lignin.

Lignin makes up roughly 20% to 40% of non-wood fiber raw materials. Traditional pulping largely removes lignin to obtain papermaking pulp fibers. Lignin is a three-dimensional networked polymer in which phenylpropane units are linked by ether and carbon-carbon bonds. Depending on the plant fiber type, its basic aromatic monomers can gain and lose electrons, absorb ultraviolet light and show potential as energy storage materials.

In the past, lignin’s value was not well developed, and pulp mills typically burned it to recover heat. Dai explains that in recent years, researchers have leveraged the special functions of lignin’s phenolic hydroxyl aromatic monomers to replace phenol in green adhesives, energy-storage electrolytes and electrode materials, UV-resistant film materials and more.

Another promising direction is high-yield chemi-mechanical pulping. It can help ease China’s bottleneck in papermaking fiber supply while offering advantages such as lower wastewater treatment difficulty and cost.

Dai says this approach abandons the old idea of extracting cellulose and leaving hemicellulose and lignin aside; instead, it uses all wood fiber components together as pulp for papermaking. High-yield chemi-mechanical pulping relies mainly on mechanical methods, supplemented by small amounts of bioenzymes and chemical additives. This greatly simplifies pulp wastewater treatment and lowers costs. It can not only replace large volumes of imported market pulp and waste paper, but also help eliminate the severe air pollution caused by burning crop straw.

Dai reveals that the paper industry has already carried out many research projects and piloted them at selected companies, using wheat straw biological pulping to make household paper, packaging paper and other products.

Bioenzymes May Drive the Paper Industry’s Green Transition

Under dual cost and environmental pressure, the paper industry is also eager to shed its image as a major polluter and become a model of energy saving and emissions reduction.

In steering the high-pollution, energy-intensive paper sector toward a greener path, bioenzyme preparations are playing an increasingly important role.

Dai says bioenzymes are highly specific and efficient. Current technical research on their use in papermaking focuses mainly on refining, deinking, bleaching and removing stickies from the papermaking process.

For example, bioenzymes can modify the cell walls of pulp fibers, helping them swell and soften faster, enhancing refining effects, reducing refining energy consumption and improving paper strength. Studies show that bioenzymes can cut refining energy consumption per ton of pulp by 41.4%.

In addition, when the paper industry recycles waste paper on a large scale, deinking is required.

Conventional deinking uses chemicals. Under suitable temperature and mechanical action, ink particles are separated from fibers, then removed from pulp by flotation, washing or a combination of both. Enzymatic deinking treats waste paper with enzymes and combines that with flotation, washing or both to remove ink.

Bleaching is another key papermaking step. Enzyme preparations can provide a “bio-bleaching aid” effect, reducing the use of chlorine-containing bleaching chemicals and thereby cutting adsorbable organic halides in bleaching wastewater and lowering environmental impact.

However, applying bioenzymes in the paper industry has not been smooth sailing.

Dai says R&D on bioenzyme technology has produced some results, but application bottlenecks remain. So far, there is no true biological pulping mill anywhere in the world, because using bioenzymes in complex, large-scale pulping still involves a series of technical challenges.

Dai also points out that bioenzyme pretreatment of raw materials takes a relatively long time, while mills need efficiency to ensure continuous production, so they prefer faster physical or chemical pretreatment. Some enzyme preparations also face issues such as high cost, limited variety, strong sensitivity to temperature and pH, and limited effectiveness. As a result, bioenzyme technology remains an auxiliary application at this stage rather than a leading force.

At the same time, Dai is optimistic about bioenzymes’ future in papermaking. In his view, bioenzymes are highly specific and efficient, and for the high-pollution, energy-intensive paper industry in particular, their environmental benefits are clear and their advantages over chemicals are distinctive. As technology advances, bioenzymes will certainly take a leading position in the paper industry in the future.

Source: This article is republished from China Packaging Network (pack.cn). Original link: http://news.pack.cn/show-378529.html