Delving into pulp facts to turn cane into paper

TURNING bagasse into paper should have been a no-brainer for the Australian sugar industry, which crushes 35 million tonnes of cane annually.

What could be better than using the discarded stalks as a feedstock for paper mills?

But the economics have been unworkable because of the crucial role of water in the paper-making process.

Put simply, it involves adding water to a feedstock pulp and, at a later stage, draining it, at which point the fibres settle and overlap each other, forming paper.

"Bagasse contains a large proportion of short fibres that block the pores of the paper, stopping the water from draining," Queensland University of Technology chemical engineer and research fellow Tom Rainey says. "This slows the production process and reduces productivity 25 to 30 per cent compared (with) manufacturing using eucalypts."

So local bagasse has remained a feedstock only for furnaces, while wood chips remain the preferred option for paper. Now, Rainey says, he has made a breakthrough in his doctoral research, funded by the federal Government's Sugar Research and Development Corporation and the Queensland Government.

"In the laboratory I worked out a way to sift out about 40 per cent of the short fibres. The challenge is to translate that process to an industrial scale." His refinement of the depithing process would make using bagasse even more efficient than eucalypt.

"At that point the economics shift. We would be able to make things such as generic photocopier paper with a cheap, local resource with high productivity," Rainey says. Even better, bagasse is valued at $30 to $60 a tonne compared to eucalyptus chips' $150 a tonne.
This would make its production a viable import replacement strategy for most of our generic paper.

It also could create a new market for cane farmers: replacing even 20per cent of the pulp wood market would yield more than $100 million a year, according to Rainey. Bagasse is also in favour with the gathering body of believers in the value of producing fuel ethanol from biomass. Rainey expects to use the biorefinery pilot plant QUT is building in Mackay to also produce bagasse pulp for paper mills.

Both uses of bagasse are a long way from commercialisation.

Certainly a lot of work remains to be done on Rainey's project. Although he says, all being well, it could take less than five years to get a sustainable industry up and running, that includes the hurdle of attracting substantial investment.

There is also further work needed on managing bagasse pulp effluent, although he says it is more easily treated than wood effluent.

"We have had some expressions of interest from a north Queensland farmers' group in trying to run our bagasse in paper mills."

But there is still a battle to be fought, convincing farmers to grow cane varieties bred to maximise fibre size. "In Argentina and India they breed cane to have good paper-making properties." That means they settle for cane varieties with up to 10 per cent less sugar than the ones used in Australia.

SOURCE: theaustralian.news