Swedish Researchers Create Nanofibers from Cellulose Sludge

Mehdi Joonobi, postdoctor and Professor Kristiina Oksman at the Department of Engineering Sciences and Mathematics at LTU.

Feb 17, 2012 - A research team at Lulea University of Technology (LTU) in Sweden is on a mission to recycle pulp mill sludge and produce cellulose nanofibers, which can be re-used to make paper and board grades.

Currently, the researchers are working with sludge from Domsjo Fabrikerna's mill in Sweden. The mill has an annual production capacity of 235,000 tons of specialty cellulose used by manufacturers of viscose (textiles) and non-wovens (hygiene products). The mill's cellulose is bleached totally chlorine-free in a closed-loop bleach plant.

According to LTU's researchers, the mill creates about 1000 tons of residual sludge per year, which is not re-used, and so far, their research project is proving to be an economic and environmental success.

"This is definitely the best result we have had in producing nanofibres from different bio-residues. Presumably, this is a very profitable production that more cellulose industries should take an interest in," said Kristiina Oksman, a professor at LTU.

The researchers noted that the particular sludge from Domsjo makes it possible to produce the most profitable production of cellulose nanofibres from bio-residue products, to-date. The yield from the process of manufacturing cellulose nanofibres from the sludge is 95%, compared with cellulose nanofiber production from wood chips 48%, lignin residues 48%, carrot residues of 20%, barley 14% and grass 13%.

"The separation of cellulose nanofibres from bioresidues is energy-demanding, but when we separate the waste from Domsjo, the energy consumption is lower," Professor Oksman said.

"The special cellulose from Domsjo has very small size and it also has high cellulose content and therefore the fibers do not need to be chemically pre-treated before the production of cellulose nanofibers," Oksman explained.

The research team noted that cellulose nanofibers manufactured from this sludge are probably shorter than the cellulose nanofibers made from pulp, but are finer and can form dense films with excellent barrier properties.

For example, potential uses for the recycled sludge could be less costly, more environmentally-friendly liquid board to produce milk cartons. Many other paper and packaging applications would also be possible.

"Our goal in this project is to create new materials, use residues, and thereby increase the value of the whole production chain. Now, Smurfit Kappa has also shown interest for us to investigate the conditions for their cellulose sludge," Oksman said.

LTU's research is part of the project Bio4Energy.

For further information contact Katarina Karlsson: katarina.karlsson@ltu.se

SOURCE: Lulea University of Technology