Pelletizing Pine

By: Grace Jones

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Posted: 6/30/2022

Pelletizing Pine Photo By: Dominique Belcher

The U.S. exported nearly 7.26 million metric tons of wood pellets in 2020, up five percent from 2019, according to the USDA Foreign Agricultural Service. Due to the rising interest in this energy source across the globe, researchers in the Forest and Wildlife Research Center seek to develop a cost-effective reliable material that is sturdier in transport and burns cleaner when consumed.

U.K.-based renewable energy company Drax has partnered with Dr. Jason Street, associate professor in the Department of Sustainable Bioproducts, to discover solutions to common problems seen in wood pellets, such as pellet deterioration during transport.

"We are attempting to create a hotter burning wood energy pellet that has less of-gassing when compared to traditional wood pellets. The idea is to see if we can transform low-value products into high-value products and increase profit-ability values for timber producers," Street said.

They started their research by testing alternative additives in the pelletizing process. Traditionally, cornstarch is used as an additive to produce pellets. Street and his team began with materials like bio-char, bio-oil, sweet potato, vegetable oil, and other various additives to produce pellets in a laboratory.

After attempting the production process in a laboratory setting, they transitioned to an industrial-sized production to mirror the normal production process of pellets.

"We were trying to produce pellets on a lab scale using a novel pneumatic system and then a hydraulic system to try and improve the pressure and mimic the temperatures," Street said.

They found that their team could mimic one aspect of the industrialized mill production process at a time but incorporating multiple aspects of industrial-sized production wasn't ideal in the laboratory setting.

The team accessed an industrial-sized mill at the MSU Pace Seed Lab and obtained data that would be more useful for industries using large equipment instead of only testing with bench-top lab systems.

"Using the Sprout Waldron mill allows industrial pellet producers to be able to determine the outcome they can expect in power requirements and pellet quality. We have found that the characteristics of pellets made using a lab bench-top press and small heated die to produce pellets do not compare as well to the characteristics of pellets made with industrial equipment," Street said.

Tyler Lowe, an industrial and systems engineering graduate student who works in the lab, explained that with this research, they can utilize natural resources, which helps satisfy the regulations the industry has established.

"A lot of the additives we are trying in the different wood pellets are materials that are not being utilized anymore. We are taking waste products, recycling and reusing them, and creating recycled products that are enhancing the pellets," Lowe said.

The production process for wood pellets is meticulous. The team had to closely analyze many variables that affect the outcomes, such as the additives used, the moisture content of the pellets, and the pressure and heat applied to the pellets.

"One thing that surprised me was all the different tests we had to conduct. There are so many different aspects of the pellets, like the moisture content, you have to learn to understand the dynamic between the wood and additives being used," Lowe said.

Now, the bio-oils and biochar researched are in the approval process. This will determine if the production and additives meet the environmental criteria set forth by Drax.

"There is a great potential for wood energy pellets to help improve heating systems. We reported the potential we found during production using certain additives," Street said.

After three years of research, the partnership with Drax is yielding results. The researchers have found ways to make a better, stronger pellet that burns cleaner and costs less.

This research is funded by Drax and the Forest and Wildlife Research Center.

Forest Products