Waste screening technologies: which one fits your next recycling plant?

Disc screens, trommels, vibrating or star screens: a technical comparison

When designing a new waste treatment line, or upgrading an existing one, screening technology is often seen as a secondary choice. In reality, it plays a much bigger role in overall plant performance than expected. It affects energy consumption, maintenance planning, plant footprint, and the quality of the output fractions; ultimately having a direct impact on the overall economics of the operation.

The market offers several different approaches: trommel or drum screens, vibrating screens, star screens, disc screens. Each with its own strengths and limitations depending on the application.

Disc screens, trommels, vibrating or star screens: a technical comparison

Trommel screens are based on a rotating drum with perforated sections, where material is gradually separated as it moves along the cylinder. Smaller particles fall through the perforations, larger ones exit from the far end. Trommels are mechanically simple and have been widely used for decades, particularly in MSW and compost applications.

Vibrating screens separate material through high-frequency mechanical vibrations across a mesh or grid. The vibration causes fine particles to pass through the mesh while coarser material moves to the end of the deck. Because of the forces generated, vibrating screens typically require reinforced concrete foundations to manage structural stress.

Star screens use parallel rotating shafts fitted with star-shaped elements, usually rubber or polyurethane, that agitate and advance the material. Finer fractions fall through the gaps between the stars; bulkier material continues forward. They perform reliably in compost refining and wood processing, though their range of compatible materials is narrower than other technologies.

Disc screens, in their traditional form, work similarly to star screens but use disc-shaped elements on rotating shafts. In Ecostar’s Dynamic Disc Screening (DDS) and Hyper Dynamic Disc Screening (HDDS) systems, the key difference lies in the design of the drive shaft itself: free manifolds (elements independent of the shaft’s rotation) are fitted around it, preventing fibrous or long materials from twisting around the shaft or clogging between the discs. The hexagonal or octagonal disc profile causes material to bounce dynamically across the full screening surface. Thanks to this design, the material flows on the screen’s discs and is subjected to a jolting movement that separates the waste. The undersized material drops below the screening surface, passing through the gaps between the discs while the oversized material advances to the end of the screening plane. The result is a clean fraction, ready for recycling processing.

Looking at the main differences in more detail, each technology responds differently depending on the operating conditions.

Disc screening vs. trommel: a comparative overview

The trommel’s fundamental constraint is its dimensions, and consequently plant footprint, due to the fact that material can only be screened when it contacts the lower portion of the drum.

A documented example: two trommel screens with a combined length of 25 metres were replaced with a single Ecostar disc screen measuring 9 metres, achieving the same production volume, with improvements in screening quality and lower energy and maintenance requirements. Read the full comparison.

The following figures are drawn from Ecostar’s internal technical documentation and should be considered indicative. Actual results may vary depending on material composition, operating hours, local energy costs, and specific plant configuration.

In this scenario, Ecostar disc screens grant:

• Reduced operating costs per ton
• 37% shorter payback period
• flexibility: the screening size of disc screens can be adjusted in real time (±30%) by varying shaft speed via inverter; on the other hand, changing the screening size in a trommel means changing the drum.

Disc screening vs. vibrating screens: a comparative overview

Disc screening vs. star screens: a comparative overview

Star screens are a solid choice to treat and screen compost and wood; however they tend to be less flexible when handling more heterogeneous material streams. Disc screens are built to handle MSW, RDF, C&D waste, incineration ash, biomass, compost, wood — essentially the full spectrum of what a modern waste treatment or recycling facility might process.

On durability: rubber and polyurethane stars wear gradually and lose dimensional precision over time, which means the screening section drifts from its target value. Ecostar discs are manufactured in Hardox wear-resistant steel, and under normal operating conditions, typically only the first 4 to 6 shafts require replacement annually.

Traditional disc screens vs Ecostar disc screens with DDS/HDDS technology: a comparative overview

In a documented case study, a traditional 8-metre disc screen was replaced with an Ecostar Hexact 8000 in an MSW and compost pre-treatment plant. The comparison was carried out under identical throughput (25 t/h) and screen length (8 m). These results are mainly linked to the use of Hardox wear-resistant discs and the HDDS anti-wrapping system, which help prevent clogging and reduce wear over time.

The following figures are drawn from a real application case study and should be considered indicative. Actual results may vary depending on material composition, operating conditions, and local energy costs.

How to choose the most suitable screening technology for your project?

There is no universal answer. The right choice depends on the specific context of the plant, the materials being processed, and the operating conditions. Each technology has its own area of application where it can perform effectively.

For plants handling consistent and homogeneous material streams, simpler technologies may be sufficient. In more complex scenarios (mixed waste, variable moisture content, or fibrous materials) factors like wear, clogging, and downtime tend to play a more significant role over time.

Other aspects, such as available space, energy costs, and maintenance strategy, should also be considered early in the design phase, as they can have a long-term impact on operational efficiency.

Screening waste with Ecostar DDS e HDDS technologies

Ecostar’s screening range is built around two disc screening systems:

• DDS (Dynamic Disc Screening)
• HDDS (Hyper Dynamic Disc Screening).

Both are available across three machine lines:

• the stationary Hexact for fixed, high-throughput applications; the mobile Hextra for operational flexibility at larger capacities; and Nhexa, the mobile screen introduced in 2025 for low and medium throughput applications.

For more detailed insights on specific applications or materials, the Ecostar team is available for technical consultation. Contact us through the dedicated form.