Chlorine-free "salt-free" bleaching technology (1990s, Daishowa Paper Company)

Chlorine-free "salt-free" bleaching technology (1990s, Daishowa Paper Company)
In the 1990s, Japan's paper industry was under pressure to reduce water pollution caused by chemicals and shift to a production system with less environmental impact as the next phase of its anti-pollution measures. In particular, chlorine gas and hypochlorous acid, which had been used in pulp bleaching, were internationally recognized as a cause of AOX and dioxin emissions, and Europe and the United States were shifting to chlorine-free bleaching methods such as ECF and TCF. In response to calls for higher environmental standards in Japan, Daishowa Paper Mfg.
The "chlorine-free bleaching technology" introduced by the company does not use any conventional chlorine chemicals, but instead uses a stepwise combination of oxygen bleaching, ozone bleaching, and hydrogen peroxide bleaching to bleach pulp to a white color. The use of ozone and other highly reactive chemicals efficiently decomposes lignin and minimizes toxic byproducts. As a result, the environmental impact of the wastewater was greatly reduced, which had a direct effect on the preservation of the river environment around the mill.
Furthermore, the introduction of salt-free bleaching was not merely a matter of replacing chemicals, but required a review of the entire process, including pulp pretreatment, control of reaction temperature and pressure, and improvement of wastewater treatment facilities, providing an opportunity to promote the sophistication of the paper manufacturing process. Daishowa Paper's implementation of this technology in its industrial paper line was highly regarded as a symbolic corporate environmental initiative, and played an important role in the Japanese paper industry's transition to a sustainable production model.