Best available technology: ECF, TCF, Closed Loop?

Northern Pulp is a producer of high quality bleached kraft pulp used in the production of tissue, paper towel, copy paper and many other daily use items. As you will notice, these products are typically white in colour, which requires bleaching.

We currently operate an Elemental Chlorine Free (ECF) process that uses chlorine dioxide for the bleaching of wood pulp. There have been suggestions that we change to a Totally Chlorine Free (TCF) process with a closed loop system as part of the transformation.

As part of our transformation, we are committed to implementing best available technology for a bleached kraft pulp mill to reduce the environmental impact of our operations. If TCF and/or a closed loop system were viable for our operations, we would include them in our plans. Unfortunately, today they are not viable options.

Bleached, chlorine-free kraft pulp is categorized as either totally chlorine-free (TCF) or elemental chlorine-free (ECF). TCF pulp is produced with pulp that has been bleached by using ozone and hydrogen peroxide, or that has not been bleached at all. ECF pulps, like those produced by Northern Pulp, are produced from pulp that has been bleached with chlorine dioxide (ClO2), but without elemental chlorine (Cl).

The bleaching process is designed to bleach the pulp by removing all the residual lignin from the pulp in a step generally referred to as delignification. Up until the mid-1990s, elemental chlorine (Cl) was used to bleach the pulp to produce the desired brightness. However, concerns about the environmental impact prompted one of the most important implemented changes within kraft pulp mills, whereby elemental chlorine was completely replaced by chlorine dioxide (ClO2) as the bleaching chemical. Chlorine dioxide was key to the development of the ECF bleaching process.

Northern Pulp converted to the ECF bleaching process in 1997, with this technology currently being the most common bleaching method worldwide.

ECF and TCF are both considered best available technologies. Many mills of both bleaching techniques have attempted to close the effluent loop in their fully bleached kraft mills, but none have managed to develop a totally closed loop or effluent free system. The Province of Nova Scotia retained an engineering firm to study this further and concluded that, “Closing the loop is not an option for Northern Pulp.” You can view the report here: https://openinformation.novascotia.ca/FOI-Requests/2019-08311-TIR/shyb-bce4

The best available techniques for bleached kraft mills utilize oxygen delignification in combination with primary/secondary effluent treatment and in some cases tertiary treatment. Our proposed transformation includes both oxygen delignification and tertiary treatment.

A few bleach kraft pulp mills were retrofitted to TCF, as TCF pulp had a better environmental image at that time and the environmental impact was believed to be more easily controllable. Today, it is understood that the perceived environmental benefits were not realized. Additionally, the market volume of TCF pulp remains much smaller than ECF mainly due to pulp quality issues, creating questions about the long-term sustainability of TCF mills.

KSH, a Montreal, Quebec-based engineering firm with expertise in pulp and paper, has done a lot of work in Best Available Technology (BAT), ECF, TCF and closed loop systems. KSH was retained by Northern Pulp to develop the transformation concept based on the feedback and input we received with the Environmental Liaison Committee, the community, and other stakeholders over the past few years.

In its Best Available Technology assessment for Northern Pulp, KSH noted the following differences in wastewater between the ECF and TCF:

“Best Available Technology (BAT) has legal status in both the USA and Europe when determining consents for the discharge of effluent: in the USA, the Elemental Chlorine-Free (ECF) process is regarded as being Best Available Technology while in Europe, the EU Commission on the Environment has decided that there is no significant difference between Totally Chlorine-Free (TCF) and ECF and, therefore, both are regarded as BAT. The EU Commission further stated that there is no clear difference in toxic effect patterns and effect intensity between effluents from mills using low-kappa ECF and TCF bleaching.”

Additionally, power consumption in the production of TCF is approximately 13% higher than ECF pulps due to the energy intensive production of ozone which will lead to higher greenhouse gas emissions. The advantages of ECF bleaching are lower energy consumption, better fibre properties, and better yield than with TCF, thus saving natural resources.

We appreciate the ideas and questions being generated, so far. Please submit your questions and ideas for our consideration.