Presidential Green Chemistry Challenge: 2001 Greener Reaction Conditions Award
Novozymes North America, Inc.
BioPreparationTM of Cotton Textiles: A Cost-Effective, Environmentally Compatible Preparation Process
Innovation and Benefits: Novozymes North America developed BioPreparationTM, a technology to separate natural waxes, oils, and contaminants from cotton before it is made into fabric. This technology uses enzymes instead of corrosive chemicals and could save 7–12 billion gallons of water each year.
Summary of Technology: In textiles, the source of one of the most negative impacts on the environment originates from traditional processes used to prepare cotton fiber, yarn, and fabric. Fabric preparation consists of a series of various treatments and rinsing steps critical to obtaining good results in subsequent textile finishing processes. These water-intensive, wet processing steps generate large volumes of wastes, particularly from alkaline scouring and continuous/batch dyeing. These wastes include large amounts of salts, acids, and alkali. In view of the 40 billion pounds of cotton fiber that are prepared annually on a global scale, it becomes clear that the preparation process is a major source of environmentally harsh chemical contribution to the environment.
Cotton wax, a natural component in the outer layer of cotton fibers, is a major obstacle in processing textiles; it must be removed to prepare the textile for dyeing and finishing. Conventional chemical preparation processes involve treatment of the cotton substrate with hot solutions of sodium hydroxide, chelating agents, and surface active agents, often followed by a neutralization step with acetic acid. The scouring process is designed to break down or release natural waxes, oils, and contaminants and emulsify or suspend these impurities in the scouring bath. Typically, scouring wastes contribute high biological oxygen demand (BOD) loads during cotton textile preparation (as much as 50 percent).
Novozymes's BioPreparationTM technology is an alternative to sodium hydroxide that offers many advantages for textile wet processing, including reduced biological and chemical oxygen demand (BOD/COD) and decreased water use. BioPreparationTM is an enzymatic process for treating cotton textiles that meets the performance characteristics of alkaline scour systems while reducing chemical and effluent load. Pectate lyase is the main scouring agent that degrades pectin to release the entangled waxes and other components from the cotton surface. The enzyme is also compatible with other enzymatic preparations (amylases, cellulases) used to improve the performance properties of cotton fabrics.
The practical implications that BioPreparationTM technology has on the textile industry are realized in terms of conservation of chemicals, water, energy, and time. Based on field trials, textile mills may save as much as 30–50 percent in water costs by replacing caustic scours or by combining the usually separate scouring and dyeing steps into one. This water savings results because BioPreparationTM uses fewer rinsing steps than required during a traditional caustic scour. Significant time savings were also demonstrated by combining treatment steps. A recent statistical survey determined that 162 knitting mills typically use 24 billion gallons per year of water in processing goods from scouring to finishing; the BioPreparationTM approach would save from 7–12 billion gallons per year of water. In addition, field trials established that BOD and COD loads are decreased by 25 and 40 percent, respectively, when compared to conventional sodium hydroxide treatments. Furthermore, these conservation measures translate directly into cost savings of 30 percent or more. As such, this patented process provides an economical and environmentally friendly alternative to alkaline scour systems currently used in the textile industry.