The ultimate tissue - green and fossil-fuel free

By  PPI Special Report

BRUSSELS, Feb. 19, 2013 (RISI) - Södra Cell Värö, Sweden, has earned its place in the pulp mill hall of fame as an environmental forerunner. Since its unremarkable beginnings in 1972 with a capacity of around 220,000 tonnes/yr, the Swedish mill's claims to celebrity status include its pioneering of totally chlorine-free (TCF) bleaching in 1993, and the installation of a bark kiln in 2010 which made it the first pulp mill to be fossil fuel-free in routine operation.

Värö shares with its sister mill at Mönsterås the distinction that it operates both a pulp mill and sawmill on the same site. The pulp mill supplies energy to the sawmill's drying kilns and the sawmill supplies bark and cellulose chips to the pulp mill - a highly energy-efficient setup. The residual heat from the pulp mill heats the sawmill's kilns, so that the need to burn bark for this purpose is minimized. Another advantage of this "polygeneration" is reduced transport of raw material.

With a capacity today of some 425,000 tonnes/yr of softwood kraft on a 64-ha site, Värö plays a key part in Södrä Cell's annual pulp production which amounts to about 2 million tonnes, some 90% of which is softwood. Investments in the past decade at the mill include a new biological wastewater treatment plant, new turbine, causticizing unit, evaporation unit and the bark kiln mentioned. Värö processes more than 2.1 million m³/yr of wood, excluding bark, drawing from an average radius of 120 km. It generates 320 GWh/yr of energy, or which 65 GWh is delivered to the electricity grid and 120 GWh/yr goes to the local town of Varberg in the form of district heating, 50% of the town's needs.

The ideal tissue pulp

The mill's significance in the paper market has shifted somewhat in the last few years. The proportion of Södrä Cell's sales to the tissue sector has risen to around 40% - approximately double what it was five years ago - and some 50% percent of Värö's output is supplied to tissue mills.

Värö's importance for tissue is based on its production of Södra BlackZ - a mainly spruce thinnings-derived pulp which is particularly suited to tissue thanks to its combination of high tensile strength and fiber length which enables it to create structure in the furnish. The tissue paper produced from BlackZ is not only soft, but also very absorbent. Värö produces most of Södra's Black pulp, but there is some production at both Mörrum and Tofte. Some paper specialties specify BlackZ, but it is mostly used for tissue.

The chlorine-free bleaching process which Södra adopted has proved to be somewhat gentler than that of Södra's competitors, according to the company's head of tissue, Marcus Hellberg. "This is something of an unforeseen benefit of the bleaching process at Värö and our other mills", he admits, "but feedback from customers is that the TCF process we use is less aggressive than other TCFs so the pulp structure is less affected." With improvements to the ECF process, TCF does not drive business to Södra in the way it used to, although some customers do still require it.

The key environmental parameters from the customer perspective are certification (Södra's production is mostly dual certified to PEFC and FSC) and water footprint. The latter has started to be a significant issue, according to Hellberg, with many customers interested to cooperate in Södra's water footprint project as they see it as a key element of a responsible procurement process. "It turns out that the process of pulp and paper making in Sweden comes out well under the scrutiny of water footprint investigations," says Hellberg. "In Sweden water is not a scarce resource, and since our net consumption is very low this is a competitive advantage compared to production where supply of water is limited.

The essential softwood element

Paradoxically, the drive by tissue producers to increase the proportion of hardwood in their furnish, mainly because of historical price differentials, has worked in Södra Black's favor. Hellberg explains: "As you reduce the softwood in the furnish, you reduce the element of structure, so what's left needs to be very good. This is one of the reasons BlackZ has grown in popularity. Tissue manufacturers are seeking us out more and more to help them with particular challenges in terms of getting the furnish right."

In response to demand, Södra has ramped up production of Black over the past two years at Värö, and the onsite R&D facilities have been used to the full to optimize the grade's use for tissue. BlackZ is now produced in two variants offering different levels of brightness.

But while process factors requiring specific investments have been important in establishing BlackZ's characteristics, it is fundamentally a pulp whose properties are based on the raw material from which it is derived. This puts a limit on Södra's output of BlackZ. It is a question of how far it is practical and economically viable to transport the particular thinnings used to produce BlackZ. Värö's proximity to the forests of western Sweden reduces transport distances for raw materials, and shipping the finished pulp from the west coast of Sweden reduces transportation to international customers. Like all pulp mills, its positioning is strategic and it would be unwise to dilute such advantages. To increase the capacity of BlackZ indefinitely is simply not an option.

Black and blue

If the capacity for Södra BlackZ is finite, the alternative of Södra BlueZ is still very suitable for tissue, according to Hellberg, even if it has found itself somewhat in Black's shadow. Värö produces some Blue, as indeed do all four Södra mills, but Mönsterås is the bulk producer of this grade.

Black has the advantage that it requires relatively little refining to achieve good tensile strength, with the energy-saving benefits which accrue from that. However, as Hellberg points out, "When customers refine at a certain level anyway as part of their process, then Blue is a particularly good option, because it is a very good pulp for tissue production."

Södra might be primarily a softwood business, but it is not leaving all hardwood activity to the powerhouses of short fiber pulp, most of which are in Brazil. Södra Gold is based on birch. It mixes very well, says Hellberg, and provides particularly good softness, so if anything, Södra believes it has a premium hardwood pulp on its hands which should be distinguished from eucalyptus.

Striving for better

But the future for tissue pulp at Södra remains predominantly with softwood, and this is the focus of current research. Two parallel projects looking at further options for tissue customers are underway, with lab and machine trials in progress. With both raw material mix and process under scrutiny, Södra hopes to offer something of significant value to the market which, with sufficient interest, could be in commercial production next year at Värö. Details are scant at this stage, but Hellberg confirms that, apart from these projects, the next step for Värö is to invest further in capacity, as far as possible, and quality.

Tissue grades now represent more than a quarter of global demand for chemical market pulp. At the same time mechanical papers, namely newsprint, are in decline. As a prime source of recycled fiber for tissue producers, newsprint's long-term decline means that there will ultimately be less recycled fiber available on the market. For tissue producers, this will mean a greater dependence on virgin fiber and an increasing need to optimize efficiency and value in their use of market pulp.

Södra faces the same challenges as the rest of the industry, created by the poor prospects for certain paper grades. But with Värö's focus on tissue with its more rosy future, and precious little new softwood capacity in the pipeline, the mill has everything to fight for.

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