Earlier this year, paper engineers at a German paper mill noticed a significant “dirtying” of the paper pulp, with “alarming” numbers of dirt specks showing up in control samples. Ultimately, liquid toner prints from a photo book printer were identified as the source.
Although the percentage of liquid toner prints was less than 10% of the total volume of recycled stock being processed, the mill ultimately diluted the stock even further. Ultimately, the mill’s report concluded that liquid toner prints not be used for recycling.
In today’s world of green everything, this report really caught my eye. HP has long indicated that its prints are de-inkable, but as the volume of digitally printed photo books grows, the question becomes whether these extremely heavy coverages change the de-inking equation. If so, what impact does this have on recommendations for de-inking of liquid toner prints?
I contacted HP for its take on the issue. It took a little while, but here is the response from Jeffrey Belson, regulatory manager, Indigo division, HP:
HP has not seen or analyzed print or pulp samples from the incident INGEDE described in its Oct. 2010 press release on a German deinking mill. HP has already established plans to engage with the mill described in the press release to help assess and understand this incident.
HP Indigo’s Deinking Research program, and HP’s expertise in printing technology, could be of significant assistance in identifying the prints involved, analyzing the deinking mill incident and supporting additional tests as appropriate.
The Deinking Research program continues to emphasize collaboration, scientific research and the identification of solutions that meet the common objectives of the paper-making, printing and deinking industries.
Western Michigan University, working under the direction of NewPage Corporation, has completed a successful pilot-scale trial that confirmed deinkability of a batch consisting of 5% HP Indigo prints (a random mix of customer prints) and 95% standard mixed office waste furnish using NewPage’s standard process conditions.
HP considers this positive pilot trial result and additional research from HP’s Indigo division to provide a foundation for understanding deinkability at other wood-free deinking mills.
Note that the trial was 5%, while the German mill was working under a 10% max, so the volume of liquid toner prints could have been up to double what was used in the NewPage trial. We also don’t know the coverage used in the NewPage trial and how this might affect the percentage of liquid toner prints allowable in a batch.
Clearly, we still have a lot to learn about the impact of digital inks on the recycling process. Watch for this to grow on the radar screen with the tidal shift toward inkjet, as well.