Digital

Is digital greener than litho? The short answer is ‘I don’t know’. This question was raised at a recent conference and at the time, I for one, assumed digital would be the more environmentally friendly option. After all, there are no plates or harmful chemicals in the digital print process. On further consideration, though, it’s not so obvious.

Meaningful comparison between conventional and digital printing must consider their overall impacts, not one job in isolation. While an obvious benefit of digital printing is to produce a small quantity economically, offset is reducing its set-up time and waste. For instance, Heidelberg claims a customer found the breakeven against digital at just 130 copies for its Anicolor B3 Speedmaster. Conversely, digital jobs run on-demand with little makeready waste and reprinting updates is easy so there is no need to print additional copies just in case. Equally, the fact that digital has no inks, alcohol and press chemistry that involve VOCs (although vegetable oil-based ink helps), curries favour.

Digital downsides
But digital has its downsides. Some colorants are difficult to remove in recycling and some toner cartridges are sent to landfill where ink residue may leach out. Paper choice can be limited to approved grades that are rarely recycled or FSC certified. Distribution of small quantities of paper to digital presses gives a high carbon footprint for delivery compared to bulk pallets and reels. High-end digital presses are rated at 1m SRA3 impressions per month. In comparison, today’s perfecting litho B3 runs at 13,000cph and could produce that volume in 40 hours. Including makereadies and operating 24/7, it is capable of producing more than 10 times the volume of a digital machine. Large formats are proportionately more productive, and web and gravure machines much more so on a per-print basis, therefore litho has less impact than digital.

Total energy consumption of a digital press is lower than a large offset press, but if not used overnight, the digital press will be left on standby consuming electricity to keep the fuser ready to use while the press is powered down. The energy use per A4 sheet is less for offset and gravure than for digital which loses out, just as it does when the impact of paper used is considered.

Digital grades are more specialised and made in lower quantities than offset grades and relative distribution costs are significantly higher per tonne.

Let’s compare the lifecycle analysis of the machinery. Offset presses can run for 5-10 years and then be sold for more use before scrapping and recycling. Digital presses are superseded every couple of years and have many electronic controls that are replaced consistently. Some components, such as organic photo-conductive drums, use harmful materials such as selenium that are difficult to recycle. Other electronic components have high environmental impacts compared to heavy manufactured goods like offset presses, that consume roughly their weight in fossil fuel.

Most manufacturers recycle cartridges, or they can be collected by charities for recycling, but the miles travelled may be high. Toner particle size is reducing to 8-10μm through new technologies such as emulsion-aggregation which provide better colour reproduction and more efficient toner use. However, these finer particles can remain suspended in the air and may have adverse health effects. Unite, the union, has called on manufacturers to reduce particle emissions after a study identified toner as a potential health risk. Research by Professor Lidia Morawska at Queensland Univer­sity found many laser printers emit particles that can penetrate deep into the lungs. “Health effects from inhaling ultrafine particles range from respiratory irritation to more severe illness,” she said, recommending legislation to reduce emissions.

With industrial inkjet moving from solvent based inks to aqueous and UV curing, it will have a lower environmental impact than toner based digital print. That’s good for the environment as inkjet inexorably spreads in future. But in the great digital-litho debate, don’t immediately assume that digital is always better for the environment.

Sean Smyth is an independent ‘techie’ providing support for organisations looking to apply technology. He can be contacted at sean.smyth@dsl.pipex.com