With the CTP's Technical Conference on Deinking of Digital Prints taking place in Grenoble, followed by IMI's 19th European Ink Jet Printing Conference in Lisbon, experts were privvy to the latest developments in the field.

Research body InfoTrends said it believed inkjet currently contributes around 7% of digital print volume in document printing, but the growth of production output is likely to increase the overall inkjet share to 13% by 2015. This could lead to a tenfold increase in the amount of inkjet print in the recycled waste stream, rising from 0.05% to 0.5% by 2015.

And while some de-inking facilities may accept levels as great as 10%, according to Ingede, the body representing European deinking mills, even 2% is too great, and averages are very difficult to estimate said the organisation's Axel Fischer.

"You have huge regional variations and hot spots," he said. "Waste paper is never average."

Some 20 papers on the issue were presented at the Grenoble event, but Fischer was subdued in his assessment. "Progress is very tough," he said. "I didn't see much to celebrate."

The DPDA-sponsored (the Digital Print Deinking Alliance) studies outlined how improvements can be made through changing deinking conditions; however, Fischer was sceptical about the feasibility of making changes to the current mill deinking model of flotation.

"Everything you do for inkjet will reduce the yield for offset," he said, explaining that the current process has been developed for the hydrophobic ink properties of offset print, which makes up 90% of the waste stream going into these mills. Making changes to accommodate hydrophillic inkjet reduces the overall yield, and creates more waste because the fibres themselves are hydrophillic.

"For example, these mills process 2,000 tonnes of paper every day. If you changed conditions so that you could process 5 tonnes of inkjet, then even a 1% reduction in yield would mean 20 tonnes less product and 20 tonnes more waste," he said.

Fischer said the most promising developments presented were centred on ink technology. "Some resin-based inks appeared to show good de-inkability," he said, pointing to companies such as Japanese pigment manufacturer Kao, which showcased its coated pigment inks that coagulate to form larger particles that are therefore easier to lift off the substrate.

Other alternatives involve processes where the substrate is precoated, forming a barrier between the ink. He also said that Xerox's solid ink also showed good de-inking properties.

Ingede is also working with the DPDA on joint research, but Fischer said progress was slow. "We started work on some joint testing in February, but it is going slowly. We have no prints, no tests, and so no results," he said.