Pulper waste is one of the most burdensome waste streams for a paper mill. This article explains how an integrated treatment plant works, which materials it recovers, and what economic results are documented in real-world applications.
In the papermaking process, the pulper separates cellulosic fibers from water and other materials present in recovered paper. What remains — pulper waste, also known as "pulper rag" — is a heterogeneous mixture with high moisture content, composed of:
| Component | Typical % in Waste |
| Plastics (films, laminates, polymers) | 45–60% |
| Residual fibers | 10–20% |
| Moisture | 20–30% |
| Ferrous metals | 4–6% |
| Non-ferrous metals | 1–3% |
| Inert materials and contaminants | 5–10% |
Direct disposal to landfills or as RDF (Refuse-Derived Fuel) involves significant and rising costs. For a paper mill producing 10,000 t/year of paper, pulper waste can represent 3–8% of the incoming material: volumes that directly weigh on the operating margin.
The process is divided into three successive phases: separation, treatment, and valorization.
Shredding
The raw material is fed via a steel apron conveyor belt and subjected to size reduction through a single-shaft shredder, sized according to the material and the required capacity. The POLLUX Rotor — a patented technology with adjustable aggressiveness — allows for varying the diameter and aggressiveness of the cutting tips based on the material, featuring bolted and easily replaceable wear parts. Downstream, an overbelt magnetic separator automatically intercepts and removes ferrous metals.
Treatment
A friction washing centrifuge breaks down the material and separates residual fibers through a combined mechanical action with water. The washing tank removes heavy contaminants and inert materials by specific gravity. Stainless steel dewatering screws and a dewatering centrifuge progressively reduce the water content.
Valorization
The material is refined through a granulator mill and industrially dried. The dried product, accumulated in a buffer silo, can be directed — depending on the chosen configuration — to pelletizing or densification (both optional), producing a stable, storable, and marketable output.
| Fraction |
Destination |
| Plastic fraction | Energy recovery or RDF |
| Recovered fibers | Reintroduction into the paper cycle |
| Ferrous metals | Steel supply chains |
| Non-ferrous metals | Metallurgical supply chains |
| Residual inert fractions | Disposal or secondary recovery |
On an installed plant with a capacity of 190 t/month of pulper waste:
Material sent for disposal: ~68 t/month (out of 190 t/month input)
Ferrous metal recovery: ~9.5 t/month
Disposal cost reduction: ~€220,000/year
Revenue from sale of recovered metals: ~€20,900/year
Total economic benefit: ~€241,000/year
Estimated payback period: approx. 6 years
Note: The data include the reduction in disposal costs and revenue from the sale of metals. They do not include any local incentives for waste management.
The composition of the pulper rag continuously changes depending on the quality of the incoming recovered paper. A non-configurable plant, which operates on a standard composition but degrades when out of specification, is not a reliable industrial solution.
CAMEC plants are custom-designed: machine size, hourly capacity, and sequence of phases. Before the final design, CAMEC analyzes the actual material coming from the customer's plant.
The direction of European regulations on industrial waste is clear: increasing recovery targets, structurally rising landfill costs, and incentives for material recovery. Those who invest today do so in a still favorable context; those who wait will do so under more expensive conditions.
Pulper waste is not an unsolvable problem: it is a heterogeneous material stream that, with the right technology, turns into material recovery and operational cost reduction.
CAMEC has been designing and manufacturing custom-built plants for over thirty years, with dozens of references in the paper industry across Italy and Europe.
Want to evaluate if a CAMEC plant is the right solution for your paper mill?