Nonwood Pulping

It’s no secret that the pulping industry has been dominated by wood over recent years. If you ask anyone what paper is made of, they will say, “trees.” However, that wasn’t always the case. As recent as the late 1800’s, nonwood fibers were the most popular option for anything pulped, due to their availability and the industry’s familiarity. Today, we are seeing a return to nonwood pulping, specifically with sustainable materials, mostly due to environmental pressures and new market opportunities. In reaction to this return, let’s have a quick refresher on nonwood pulping.  

What are Nonwoods? 

Nonwoods are any plant materials that do not come from trees and can be used for pulp and paper. As you can imagine, this covers a wide variety of raw fiber, including cotton, rice, wheat, corn stalks, papyrus, grass straw, hemp, and kenaf. 

How did we get here? 

Pulping Machine

The recorded history of pulping began in 3000 BC, when Egyptians began using papyrus to create paper. The exterior of the reed was laminated to form a sheet, on which Egyptians could begin to record their culture. The first true paper belongs to the Chinese. 105 A.D. is often cited as the year of its invention, but recent archaeological investigations say it may have happened 200 years earlier. In the beginning, the Chinese used bark from a mulberry tree, broke them into fibers, and pounded them into a sheet. He later discovered that he could greatly improve the quality of the paper by adding hemp rags and old fish nets to the pulp.  

For the next 1800 years or so, the convenience of the crops and the strength of the material helped ensure that nonwoods would stay dominant in the pulping industry. Pulping spread from China to the middle east, to northern Africa, and finally to Europe. In the mid-18th century, Europe was having trouble getting enough cotton and linen rags, so they searched for an easily accessible alternative. The most promising materials they could find included cereal straw and wood. This began the reign of pulped wood that has lasted to this day. However, there has been a noticeable shift back to pulping’s roots, for a plethora of reasons.  

Why choose Nonwood Pulping? 

The material characteristics of nonwoods can vary greatly, so it would be a little irresponsible of us to make a blanket statement here. Instead, we will focus on sustainable bast fibers, for which we have a lot of information.  

Quality 

For one reason, hemp and kenaf’s tensile strength is much higher than that of wood. This creates stronger, more durable products. Hemp and kenaf also have significantly less lignin content than softwood options. Softwoods tend to be 23% – 30% lignin, versus hemp’s 2% – 4% content. This makes the material much easier to pulp and color.  

Hemp FiberHemp and kenaf also provide a much wider range of length than traditional softwood options. Pulped softwood lengths usually range from 2.7 mm to 3.6 mm; hemp fiber can be processed between 5 mm and 55 mm, and kenaf can be processed between .98 mm and 7.6 mm. In Layman’s terms, the material can be processed to any specification between those figures, giving more flexibility to pulping companies and their customers.  

Bast materials, like hemp, kenaf, and flax, are also great for co-cooking with traditional wood options. Co-cooking is the term for the inclusion of multiple types of material in the pulping process with the intention to create one product. Adding bast materials to a batch can easily reduce the overall lignin and increase strength, without wholly committing to a bast pulp.  

Application 

Books - PulpingThe recent trend in pulping has been recycled paper. Though a step in the right direction, paper can only be recycled about 5 times before the material’s constitution is compromised. There will always be a need for a virgin supply to later be recycled, and strong, sustainable materials are a good choice. There are also certain industrial applications, like frozen food containers and hygiene, where recycled materials may not be the safest option. For these nonwood pulping applications, a virgin supply is necessary to keep the sustainable appeal, while also controlling for certain bacteria.  

Sustainability 

We briefly touched on this, but bast crops are some of the most sustainable in the world. Hemp can go from seed to our facility in as little as 120 days, where softwoods can take as long as 120 years (43830 days). Also, one acre of kenaf or hemp can produce as much usable fiber as four acres of timber. This replacement benefits our rare, threatened, and endangered species that rely on our forests, not to mention thousands of acres of trees. Hemp is also known for its ability to sequester significant amounts of CO2 from the environment. For every ton of hemp harvested, 1.62 tons of atmospheric CO2 is sequestered. When most companies settle for carbon neutrality, products made with hemp are generally carbon negative.  

For More Information…

If you have any questions about nonwood pulping or are interested in learning more, contact us.