Things have been far from smooth sailing for the Boyer paper mill in Tasmania’s Derwent Valley since it pulped, squeezed, and rolled out Australia’s first sheet of newsprint back in 1941.

While the mill still supplies most newspapers around the country, competition from overseas producers, waning fortunes in the newspaper industry, and changing environmental regulations have made for a tumultuous few decades. The mill has been on the brink of closure more than once.

Yet production at the Boyer mill, operated by Norwegian papermaker Norske Skog, rolls on, even as other mills around Tasmania have shuttered their operations.

Together with its sister Norske Skog mill in Albury, NSW, it churns out 425,000 tonnes of newsprint paper each year – enough to print more than 85 percent of the country’s metropolitan and regional newspapers.

The mill’s resilience is thanks in part to a partnership with chemists in the University of Tasmania’s Pulp and Paper Research Group. Over the past 30 years, Dr Karen Stack and her team have helped the Boyer mill keep its rollers turning by delving into the chemistry of wood pulp and paper at each step of the production process.

Pitch perfect

Dr Stack brings to the job an insider’s knowledge of papermaking, having worked as a chemist at the Boyer mill in the 1980s before embarking on her academic career.

In recent years, Dr Stack and her team, under the leadership of Dr Trevor Lewis, have been tackling an age-old papermaking problem: how to deal with the unwanted flotsam and jetsam that is extracted from wood pulp along with the useful cellulose fibres that are ultimately pressed into paper.

Wood resins – known in the industry as pitch – are especially troublesome. And the environmentally sustainable pines that the Boyer mill uses are notorious for their resin-rich wood. These gummy extracts stick to paper fibres, weakening the final product and transferring onto papermaking machinery, where they can tear small holes in the paper.

This reduces paper quality, and can shut down operations while pitch is cleaned away with costly chemicals, further cutting into the mill’s bottom line.

The mill’s customers aren’t keen on pitch, either. Complaints from newspaper printers who were constantly shutting down and cleaning their printing presses prompted a detailed study of how pitch can be kept in check.

Resins are sticky mixtures of organic compounds containing terpenes, such as those that give pine its distinctive aroma, as well as resin acids, fatty acids, triglycerides, sterols, and steryl esters. Resins dissolve in the hot water used for pulping, but can also form into small droplets called colloids.

Dr Stack’s investigations found that minimising temperature and acidity ‘shocks’ can keep these colloids stable, which means they don’t stick to the machinery or paper.

“In the mill, if they can try and keep things as stable as possible, then that helps with the whole chemistry of the system,” she explains.

Her team found that colloidal resins can also be more easily removed from the water using surfactants or additives, such as the mineral bentonite.

Green solutions

Dr Stack also discovered a complex interplay between resins, salts, and another extractable component of wood: hemicelluloses. Hemicelluloses are complex carbohydrates similar to cellulose, but they are soluble and don’t form into fibres.

Salts and hemicelluloses had become a problem as the mill moved towards more environmentally sustainable practices, because they were building up in the pulp water that the mill recycles.

Salts and hemicelluloses can also affect how pitch behaves. Depending on the amount of salt present, hemicelluloses can either stabilise resin colloids, or destabilise them, making them even stickier.

“There's almost a competition going on in the system between stabilising and destabilising forces,” says Dr Stack.

Armed with these insights, both Norske Skog’s Albury and Boyer mills have been able to effectively eliminate the pitch problem, and production shutdowns to clean machinery and re-thread torn paper have been reduced.

As a result, both Norske Skog mills have significantly reduced the inefficiencies caused by pitch, and money spent on expensive cleaning chemicals has also plummeted between 2009 and 2016.

While other paper mills in Tasmania have been forced to shut down in recent years, with the loss of hundreds of jobs reported in 2009 and 2010, the Boyer mill, which employs 270 people, has diversified its operations. With improvements to paper quality, the mill now produces 135,000 tonnes of magazine paper each year, in addition to newsprint.

Dr Stack and her team have also helped the mill achieve more environmentally friendly operations. Their research has given the mill valuable insights into how water use can be reduced to improve the efficiency of its effluent treatment processes.

Production improvements achieved by the Boyer mill have been rolled out to other Norske Skog mills, including its Albury mill and mills across New Zealand and Europe.

"What works in one mill – often that information is divulged to other mills that might also be having the same problem," says Dr Stack.

3 Key Facts about Norske Skog

  1. The Boyer mill now includes 135,000 tonnes of magazine paper in its annual production.
  2. Norske Skog mills in Australia produce 425,000 tonnes of newsprint and 135,000 tonnes of magazine paper annually.
  3. More than 85% of newspapers in Australia are printed on Norske Skog newsprint.

About the researchers

Dr Karen Stack

Dr Karen Stack is a part time lecturer and research fellow in the Discipline of Chemistry in the School of Physical Sciences. Her interest is in colloids and surface chemistry, in particular relating to the Pulp and Paper Industry.

Dr Trevor Lewis

Dr Trevor Lewis is a Senior Lecturer in the School of Physical Sciences (Chemistry) and Deputy Head of that School. He teaches across three campuses (Launceston, Cradle Coast and Hobart) into chemistry and environmental chemistry and into units in Human Life Science and Engineering. His contribution to teaching and research at higher degree level includes the supervision or co-supervision of 25 Honours, 3 Masters and 14 PhD students. He has strong research collaborations with the ARC Centre of Excellence for Electromaterials Science at Wollongong University and with Tasmanian and national industry.

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