Enzyme application in paper making process
Bioinnovation is helping the paper industry, traditionally seen as a large polluter, to turn a new page to better resource management. Enzymatic solutions can save paper mills time and money, as well as the environment when used instead of harsh chemicals in the pulp and paper-making process.
Enzymes in the paper-making process
The pulp and paper industry supplies consumers with 360 million tons of paper and board annually. Enzymes can help several steps of the production process of pulp and paper and by doing so save paper mills resources and reduce costs while improving the overall quality of the final paper.
Enzymes are proteins that speed up biochemical reactions without being consumed or changed by the reaction. They are found throughout nature; in our bodies, in the environment, and in all living things. With the help of biotechnology, enzymes provide an alternative to the harsh chemicals traditionally used in industry for accelerating chemical reactions. In the paper industry enzymes are used to reduce bleaching chemical consumption, modify wood fibers, improve paper machine runnability, control deposits and microbial slime, and enhance water treatment operations. The use of enzymes in the industry has grown rapidly since themid 1980s, much thanks to the ease of implementing enzymes without modifying existing processes.
Saving chemicals while producing bleached pulp
In the chemical process the wood chips are pressure cooked in a strong alkali or acid which disintegrates the chips into individual fibers. The resulting pulp contains residual lignin and a dark colored reaction product of lignin, which is produced while cooking the chips. After cooking, the lignin is washed from the fibers. The mill can optionally bleach the washed pulp to produce a pulp that can be used in production of white paper and board products. The bleaching plant normally bleaches chemical pulp with oxidative chemicals (e.g. chlorine dioxide and hydrogen peroxide) to achieve a brighter color. Lignin removal/ decolorization is a time and energy consuming process. Novozymes process known as “bleach boosting” offers a resource effective alternative. The xylanase Pulpzyme® HC prepares the fiber for bleaching by opening up the fiber structure to allow for the lignin to be washed away more easily. Removing lignin prior to further pulp bleaching saves time and energy, and decreases the quantities of chemicals used.
Time is money- reducing machine downtime
In mechanical pulp processes the sticky tree sap called pitch is still present in the pulp. The pitch, causes a lot of problems by forming machine deposits and product defects during the production of paper from mechanical pulp. Costly paper machine downtime, rejected paper, and quality problems resulting from pitch can be avoided by using Novozymes lipase, Resinase®. This lipase not only reduces downtime associated with web-breaks, pitch-coated rolls and obstructed felts, but also improves paper performance and appearance. Resinase allows the mill to use less-seasoned chips thereby easing inventory management within the wood yard. Moreover, the mill may be able to reduce the amount of expensive chemical fiber within its feedstock without loss of physical performance
From the recycling bin to paper
A mere 50% of the tree is used while producing pulp chemically and about 90% using the mechanical process. With an increasing demand for paper products and a need to care for our resources, recycled paper has received a more prominent place in paper production. Recycled paper is produced by mixing the paper with water and chemicals to dissolve the paper into pulp. To remove bits of plastic and globs of glue, the pulp is sieved through a mechanical screening process. The presence of ink from printed material and other contaminants gives the pulp a distinctive gray color which is partially washed or floated away in the deinking process. Mills can use enzymes like the cellulase Novozym® 342 and the amylase Novozym 51055 to help loosen the ink from the paper fibers, and as a result improve the extent and rate of ink removal.
The glue from, for instance, pressure-sensitive adhesives, old envelopes and magazine bindings can form problematic substances within the recycle mill known as stickies. Like pitch, stickies can lead to web-breaks, less-efficient drying and low quality end products. Mills normally use polymers and/or talc to control stickies, in combination with a mechanical cleaning process where solvents and surfactants are added. The esterase StickAway® reduces the amount of solvent and talc needed in this process. By degrading the stickies more effectively with enzymes, mills can avoid many machine stops for cleaning which translates into improved productivity and energy savings.
Enzymes doing the work of harsh chemicals
While refining, both chemical and recycled pulp papermakers can add FiberCare® R, a cellulase, to improve the overall efficiency of the refining stage and give additional value to the beaten fiber. Another cellulase, FiberCare D, can be added after the refiner to improve dewatering rates and, thereby improve mill productivity.
Regardless of process type, the production of paper requires large amounts of energy and harsh chemicals. Enzymes can do much of the work at the mill with less effort and with a lower impact on the environment. For pulp mills, this means savings on electricity, water, and chemicals, which translates into both environmental savings and significant cost savings for papermakers.