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

Chlorine-free "salt-free" bleaching technology (1990s, Daishowa Paper Company)
In the 1990s, after pollution control measures in Japan had been settled, water pollution caused by chemicals and the environmental impact of manufacturing processes emerged as new problems, and the paper industry was required to improve processes based on environmental considerations. In particular, the chlorine-based chemicals used in pulp bleaching were increasingly criticized internationally for causing AOX emissions into rivers and dioxin production, and the ECF and TCF processes, which do not use chlorine, were being developed in Europe and the United States. Against the backdrop of these trends, Daishowa Paper Mfg. made early efforts to develop chlorine-free bleaching technology.
Chlorine-free bleaching technology eliminates the use of conventional chlorine gas and hypochlorous acid, and uses a combination of oxygen bleaching, ozone, and hydrogen peroxide to whiten the pulp, significantly reducing the generation of harmful by-products. Ozone bleaching, in particular, is highly reactive and promotes lignin decomposition without the use of chlorine, dramatically reducing the environmental impact of wastewater.
The introduction of this technology required not only chemical replacement, but also a redesign of the entire process, including pulp pretreatment, temperature and pressure conditions, and wastewater treatment facilities. Daishowa Paper Company put this method to practical use on its industrial paper production line, making it a model case for both reducing environmental impact and maintaining quality. Salt-free bleaching became a symbolic technology that enabled Japan's paper industry to respond to increasing environmental regulations and shift to sustainable paper production.