Alternative raw materials: from the hemp field to paper

Status: December 29, 2021 8:15 p.m.

Waste paper has become scarce and more expensive. The paper industry is now looking for alternatives. Hemp supplies particularly high-quality fibers – the first manufacturers have gained experience with this.

In Germany, more industrial hemp was grown than ever before – a total of 5362 hectares. According to the Federal Office for Agriculture and Food, hemp cultivation in Germany has increased sevenfold in the past six years. Industrial hemp can be processed into textiles, into insulating materials for construction – but it can also be used as an ingredient in paper production.

However, hemp paper is one of the niche products in the paper market. So far there are only a few paper manufacturers in Germany who are dedicated to fiber. One of them is the Lower Saxony paper manufacturer Hahnemühle, which specializes in high-quality artist papers and custom-made products. The company has already gained some experience with the hemp fiber.

“We have had problems there before,” says paper technologist Michael Eggers. “At the beginning, when we had the first productions, there were some batches that barely dissolved and spun.” Sometimes the fibers would have wrapped around propellers or clogged some regulator and “it doesn’t go through the sorter afterwards”. In the meantime, Eggers and his team have found the right settings and developed the world’s first hemp paper for digital book printing. But since hemp is a natural product, he reckons that the process will always have to be adapted to the raw material.

Requirements for letterpress printing

For digital book printing, the paper has to be thinner and more flexible. The hemp paper from Lower Saxony therefore also consists of 40 percent cotton fibers. In addition, the paper must not be too transparent or uneven so that images and texts can be reproduced razor-sharp in the later printing process. But precisely because of the long hemp fibers, fiber accumulations can arise in one place in the paper, so-called specks.

The technical plant manager at Hahnemühle, Stefan Müller, explains what is important: “In order to avoid specks, the long hemp fibers have to be shredded after they have been mixed with spring water. In addition, the right time has to be determined later to give the paper the water to withdraw again. ” Only when these two factors are correct will the fibers be evenly distributed and produce the paper for letterpress printing.

Cultivation under strict control

Since 1996, industrial hemp has only been allowed to be grown by agricultural businesses in Germany under the strict control of the Federal Agency for Agriculture and Food (BLE). Only selected varieties with a tetrahydrocannabinol (THC) content, which is responsible for the intoxicating effect, of less than 0.2 percent may be grown. The harvest is only released after the BLE has checked the THC content accordingly.

Compared to wood pulp, the industrial hemp fibers are four to five times longer. This fiber length ensures very stable, tear-resistant and long-lasting paper in paper production. However, it is also the long fibers that make hemp difficult to process.

High manufacturing costs

Nationwide, 626 companies are dedicated to paper production. However, there is largely a lack of experience in processing hemp into paper. As a raw material in the paper industry, it is one of the so-called “other fibrous materials”, which only make up 0.4 percent of the market.

The Federal Environment Agency estimates that the production costs are around four times higher than for paper made from wood pulp. Because the machines and production processes are set up for waste paper or wood pulp processing. Switching to hemp, especially due to its nature and fiber length, is time-consuming.

Hemp in the life cycle assessment

According to the BLE, the cultivation of industrial hemp promotes sustainable agriculture. Because hemp is well suited as a so-called previous crop. It is quite undemanding to grow, robust and draws water from deep layers of the soil thanks to its long roots.

According to the Federal Environment Agency, there is currently no scientific evidence of the environmental impacts of growing hemp and processing it into paper. Such studies and evidence of recyclability would be basic requirements for the “Blue Angel for paper products” eco-label.

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