Two feedstock streams

European paper mills draw raw material from two distinct sources: virgin wood fibre harvested from managed forests, and recovered paper collected through national and municipal collection systems. The proportion of each varies by grade. Newsprint and packaging board are the highest users of recovered fibre; fine writing and printing papers tend to use a higher proportion of virgin pulp, particularly where brightness and formation uniformity are specified.

Both streams require substantial processing before they can be formed into a usable paper or board product. Virgin fibre must be converted from wood into pulp; recovered fibre must be cleaned of contaminants accumulated during its previous use.

Mechanical and chemical pulping of virgin fibre

Virgin wood arriving at a mill — typically as logs, chips, or sawmill residues — undergoes one of two principal pulping routes.

Mechanical pulping

Mechanical pulping separates fibres by physical means, either by grinding logs against a rotating stone (groundwood process) or by passing chips through pressurised disc refiners (thermomechanical pulp, TMP; or chemi-thermomechanical pulp, CTMP). These processes retain most of the wood, including lignin, meaning yields are high — typically 85–95% of the dry wood input. However, lignin causes yellowing over time, which limits mechanical pulp to grades where permanence is not required: newsprint, catalogue paper, and some absorbent tissue grades.

Chemical pulping — the kraft process

The kraft process (sulphate process) is the dominant chemical pulping method in Europe. Wood chips are cooked in an alkaline solution of sodium hydroxide and sodium sulphide at elevated temperature and pressure. This dissolves most of the lignin, leaving cellulose fibre largely intact. Yields are lower — around 45–50% of dry wood input — but the resulting pulp is significantly stronger than mechanical pulp and can be bleached to high brightness levels.

Kraft mills operate chemical recovery systems that regenerate cooking chemicals and generate energy from the dissolved organic material (black liquor). This makes kraft pulping relatively energy self-sufficient. Scandinavian and Finnish kraft mills have been significant exporters of market pulp to European paper mills for decades, though many integrated mills produce and consume their own pulp on site.

Kraft pulp dominates European packaging grades because of its tensile and tear strength — properties directly linked to the preservation of the cellulose fibre structure during alkaline cooking.

Recovered paper grading under EN 643

Recovered paper traded within Europe is classified under the European List of Standard Grades of Recovered Paper and Board, EN 643, which lists 57 grades. These are organised into five groups:

  • Group 1 — Ordinary grades: mixed paper and board, including office waste and household collections. Suitable for lower-grade board and newsprint.
  • Group 2 — Medium grades: sorted and graded newsprint, magazines. Used in newsprint and lightweight coated paper production.
  • Group 3 — High grades: white office paper, computer printout, shavings from converting operations. Used in fine paper and tissue manufacture.
  • Group 4 — Kraft grades: old corrugated containers (OCC), kraft sacks, and clippings from brown packaging. Primary input for corrugating medium and linerboard.
  • Group 5 — Special grades: including liquid packaging board and other specialist grades requiring specific processing.

Buyers and sellers specify grades by EN 643 number; contracts typically include tolerances for prohibited materials (items that cannot be pulped, such as plastics, metals, and glass). Mills running recovered fibre lines operate screening, washing, and flotation deinking stages appropriate to the incoming grade mix.

Water management and closed-loop circuits

Water is integral to papermaking: it carries fibre to the forming section of the paper machine, removes heat, and transports chemical inputs. Modern European mills operate largely closed water circuits, recycling process water between mill stages to minimise fresh water intake and reduce effluent volume.

Completely closed systems are technically difficult to achieve because dissolved and colloidal substances accumulate and interfere with paper quality. Mills manage this through partial purging, biological and physical-chemical effluent treatment, and the use of retention aids that keep fine particles and fillers on the paper machine wire rather than passing into the water circuit.

Effluent treatment plants at European pulp and paper mills typically combine biological treatment (activated sludge or aerated lagoons) with clarification and sometimes tertiary polishing stages. Discharge limits are set by national permits implementing the Industrial Emissions Directive (2010/75/EU), informed by the BAT Reference Document (BREF) for the pulp and paper sector published by the European Commission's Joint Research Centre in Seville.

Air emissions and energy

Kraft pulp mills generate characteristic odorous compounds — primarily reduced sulphur gases — from the cooking and recovery processes. Modern mills collect and incinerate these in the recovery boiler or dedicated combustion units, substantially reducing emissions compared to older plant designs. BREF emission levels for total reduced sulphur (TRS) at new kraft mills are well below those at facilities built before the 1990s.

Biomass-based energy generation is significant in European integrated pulp and paper mills. Black liquor combustion in the recovery boiler, combined with bark boilers and sometimes gasification, can make large integrated mills net electricity exporters or at least self-sufficient in heat and power.

Fibre traceability

For mills buying virgin fibre, chain-of-custody (CoC) certification under FSC or PEFC tracks material from forest to mill gate. Mixed-source mills can use percentage-based or credit systems to claim certified content in output. The relevant standards — FSC-STD-40-004 for supply chain operations and the equivalent PEFC document — specify record-keeping, volume reconciliation, and audit requirements that apply at each custody transfer point.

See the article on eco-certification in European packaging for further detail on how these schemes operate.