Producing sustainable cellulose fibers for the paper we use in our day-to-day lives has proven to be a difficult balancing act between sustainability and profitability. The sustainability element is a complex equation in itself. Collection, contamination, and lack of awareness among users make recycling cellulose fibers a major challenge, as is ensuring fibers are the result of sustainable forestry management practices. Considering that 89% of world paper production comes from wood, sustainably produced wood fiber is bound to reach a shortage. [1]
This is where hemp comes in, again actually, as it constituted most global paper production up until the “the shortage of rags threatened the monopoly of hemp and flax usage.” [1] Prior to the Industrial Revolution, paper was made from rag, which was textile or linen often from hemp. [2] No wonder, as it’s composed of 50% to 77% cellulose, which makes it 3 times richer in cellulose than wood, not to mention hemp can be re-harvested after merely 4 months of cultivation as opposed to years or even decades for trees, depending on their type. [1]
With all that in mind, researchers explored an innovative approach to preparing hemp fibers from hemp hurds, the low-value by-product of industrial hemp processing which is mostly used for animal bedding, and benchmarked paper prepared in this way against paper from hardwood pulp, the traditional source of cellulose fibers.
“To meet industrial standards, hardwood and hemp pulp fibers were mixed at a dry mass ratio of 75:25, from which tissue paper sheets were prepared.”
Moreover, they wanted to replace kraft pulping, the most popular chemical pulping process that employs harsh chemicals, with autohydrolysis, which has proven to be an efficient process for the difibration of hemp without the chemical cost of kraft pulping. Autohydrolysis employs water at a high temperature and pressure.
“The hypothesis driving the current work is that by controlling the temperature and conditions for autohydrolysis, efficient defibration in hemp will occur to provide fibers that can be used to produce tissue paper having favorable properties.”
The researchers judged how the different processing methods and cellulose fiber sources stacked up against each other by desirable tissue paper properties, such as water absorption, burst resistance, softness, and tensile strength (dry and wet).
The results were promising.
For one, hemp hurds produced a higher yield of pulp and made a roughly 4% difference in yield to the 75:25 mix with kraft hardwood pulp in which it constituted only 25%.
Furthermore, hemp pulp improved tensile index, burst resistance, and softness of tissue handsheets without taking a toll on water absorption, as hemp fibers’ chemical composition, morphology, shape, and size all seemed to augment these indispensable tissue attributes. As one example, mechanical strength improved due to “flattened morphology of hemp fibers resulting in more bonding…”
The authors conclude that “[i]n total, the use of hemp hurds fibers can lead to a variety of eco-friendly tissue and towel products that are not only highly energy efficient but avoid harsh chemical processing.” [1]
References:
- Naithani V, et al. Ecofriendly and innovative processing of hemp hurds fibers for tissue and towel paper. BioResources. 2020;15(1). Journal Impact Factor = 7.539; Times Cited = 2
- Valente AJ. Changes in print paper during the 19th century. Proceedings of the Charleston Library Conference. 2010. http://dx.doi.org/10.5703/1288284314836
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