The Craft of Recycling Kraft Paper
Have you ever wondered how different materials are recycled or why certain items are more difficult to recycle than others? Join Northstar Recycling as we explore the opportunities, processes, and difficulties associated with recycling kraft paper.
What Is Kraft?
Kraft, named for the German word “kraft,” in reference to its high tensile strength, is a type of paper product produced using the kraft process (a chemical pulping method using sodium hydroxide and sodium sulfide). Because of its high elasticity and tear resistance, kraft is widely used in packaging materials, including products like:
- Paper sacks for cement, food, chemicals, and consumer goods like flour bags
- Paper grocery bags
- Multiwall sacks
Even corrugated cardboard (OCC) is made from multiple layers of kraft paper.
Opportunities For Recycling Kraft
With so many applications, it’s not surprising to find high volumes of kraft paper in the waste streams of manufacturing companies, distribution centers, and other operations that consume large quantities of packaged commodities. For such companies, diverting kraft from the waste stream is a great way to increase recycling rates and reduce waste to landfill.
The Recycling Process
While specific recycling processes will vary depending on the constraints and requirements of each facility and recycling service provider, kraft is usually recycled similar to other paper products following these three steps:
Step 1: Sorting and Collection: The first phase of recycling kraft paper involves identifying where the material is produced throughout the facility and what it is produced as. For instance, kraft ingredient sacks sometime come with an additional poly-liner, a wax coating, or a glaze to increase the material’s wet strength and oil resistance. Not every recycling service provider will accept lined kraft materials with unlined kraft paper. Usually, facilities wishing to recycle kraft will need to separate poly-lined bags from unlined kraft. Similarly, in some situations kraft can be recycled with corrugated cardboard (OCC) while in other instances these materials must be separated. For specific instructions regarding how to sort kraft, an organization should contact their recycling service provider.
Step 2: Baling and Shipping: Once the kraft has been collected and sorted, some facilities may choose to bale their kraft for more cost efficient transportation. Baling material like kraft insures that facilities are not paying to transport air, as is the case when light materials are shipped loosely (ex. in Gaylords).
Step 3: Milling: Eventually, the kraft material will make its way from the source facility to a mill, where it will be pulped and used as feedstock for new paper products. Various stages involved in the milling process may include:
- Dispersion and Kneading
- Water Treatment
- Solid Waste Handling
Typically the recycling process ends with the kraft materials being remanufactured into new paper products, animal bedding, or some other material.
Difficulties Recycling Kraft
As with most recyclable materials, the difficulty in recycling kraft paper lies in two key areas: contamination and market rates.
Contamination Difficulties: Contamination refers to any materials or substances present beside the desired recyclable material. For instance, when recycling mixed paper, some contaminants might include dirt, grease, food waste, tissues, scrap metal, etc.
In the recycling industry, contamination can be grouped into two classifications: outthrows and prohibitive materials. Outthrows are contaminants that can be physically picked out of the recycling stream during processing, while prohibitive materials usually require chemical processing to be removed. These materials, when recycled, can damage recycling equipment or decrease the value and quality of the material they are contaminating.
Because kraft is commonly used as a packaging material, contamination often arises in instances when the material being packaged leaves a sticky or powdery residue on the kraft packaging. Industries where this is a common occurrence include food and beverage manufacturers, pharmaceutical companies, and any bakery or manufacturing facilities that use kraft paper ingredient bags (for ingredients such as flower, sugar, and various chemicals). Such residue can be difficult to remove and is usually classified as a prohibitive contaminant.
While certain recycling companies will allow for a small percentage of contaminants in some grades of material, any amount of contamination will reduce the value of a recycling material’s grade. For used kraft, where its market value relies heavily on its fiber quality, contamination can be a serious issue as it directly affects fiber quality, length, and strength.
Market Rate Difficulties: Without markets willing to purchase used kraft fiber for remanufacturing, recycling kraft can become difficult and financially burdensome for recycling service providers. Because market rates for virgin fiber can be relatively equal to costs for recycled fiber, recycling companies tend to be more restrictive regarding contamination in paper grades so as to maintain competitive fiber qualities. Therefore, kraft paper, which often contains higher levels of prohibitive contaminants due to its prevalence as a packaging material, is often considered a riskier and less desirable fiber commodity.
While current markets do exist for used kraft, there are still opportunities to improve recycling markets for this material, especially for kraft containing contamination from food, beverage, or pharmaceutical residues and the like.
One recent study from Brazil, completed June 13, 2014 by João Marciano Laredo dos Reis, José Luiz Cardoso, and Protasio Ferreira e Castro, looked into the feasibility of using kraft paper from cement bags used in building construction as reinforcement in unsaturated polyester matrix composites. As is the case with kraft packaging produced in food, beverage, and pharmaceutical companies, kraft packaging used for cement usually has very high amounts of contaminating residue that make it difficult to recycle. Hopefully, future studies like this will continue to create market outlets for these more difficult grades of used kraft, thereby making it easier to recycle.
- Mechanical Properties Of Recycled Kraft Paper Residue Polyester Composites by João Marciano Laredo dos Reis, José Luiz Cardoso, and Protasio Ferreira e Castro
- Guidelines for Recycled Content in Paper and Paperboard Packaging by the Sustainable Packaging Coalition
- Recyclable Zein-Coated Kraft Paper and Linerboard by Nicholas Parris, Marguerite Sykes, Leland C. Dickey, Jack L. Wiles, Thomas J. Urbanik, and Peter H. Cooke
- Paperwork: Comparing Recycled to Virgin Paper, Why Recycled Content is Crucial for Printing & Writing Paper by Susan Kinsella
- Contamination in Paper Recycling by American Recycling
- Paper Recycling Terminology by The Paper Recycling Coalition
- Food Packaging – Roles, Materials, and Environmental Issues by the Journal of Food Science