Detecting carbon black: STEINERT

STEINERT’s Johann Hefner speaks with Waste Management Review about developing solutions for black plastic detection.

Black plastic, often considered the problem child of the resource recovery industry, has a notoriously difficult-to-recycle composition under traditional detection technology.

Traditionally, recycling facility sensor sorters detect and measure the near-infrared spectrum of reflected light to distinguish one plastic material from another. However, because black plastic absorbs light rather than reflecting it, the material often goes unsorted and ends up in landfill.

While discussions of simply banning the product are commonplace, the problem persists. This is in large part due to its ability to make food look fresh under the harsh lights of grab-and-go hospitality operations.

A recondition of the value of convenience under current market conditions – paired with an understanding of the slow-moving nature of legislation – was the key driver behind STEINERT’s development of black plastic detection technology.

With a history dating back 130 years, the family-owned business is a world leader in sensor sorting and magnetic separation for waste and metal recycling. STEINERT’s Australian headquarters and manufacturing facility in Melbourne and test facility in Perth have been working to bring the company’s German technology to the Australian market since 2004.

According to Johann Hefner, STEINERT Sales Manager Resource Recovery, the company’s research and development strategy centres on addressing existing problems.

“Everyone involved in the plastics industry is concerned with strict legislation and a social sense of responsibility for recovering plastics,” Johann says.

“Black plastics represent a particular challenge because they cannot be detected with optical sorting technology found in standard recycling plants. While waste reduction and sustainable packaging design is the ultimate end goal, we felt it important to address the problem as it exists today.”

STEINERT began developing detection technology for challenging sorting applications in 2011, and, according to Johann, was the first company capable of detecting black plastics.

“When we developed the technology to detect black plastics, and thereby positively sort them, it was a significant breakthrough that allowed recycling rates to increase,” he says.

“By sorting black plastics from the general waste stream, STEINERT technology also facilitates pure grade sorting of the material.”

Using sophisticated airflow technology, Johann says STEINERT is able to cost-effectively sort flat and lightweight black material.

“The pure-grade separation of black polyolefins into their constituent parts, such as polyethylene, polypropylene, polystyrene and acrylonitrile butadiene styrene copolymers, allows polymer granulates to be replaced by mint-condition recyclates,” he says.

“This enables plastic processing companies to respond to the new challenges of the circular economy in a cost-effective manner, equipping them for all processes involved in plastic recovery.”

The nature of STEINERT’s technology, Johann says, allows operators to process at a large-scale industry level. He adds that via this technology, operators can separate and upgrade plastic residues to a plastic granulate, with properties similar to those found in primary raw material.

Upgrading residues to the level of raw material allows the waste to be used to manufacture durable quality products – meaning new plastics can be replaced with recycled materials.

Johann says STEINERT technology, including UniSort Black, UniSort BlackEye and UniSort Film, all use hyperspectral imaging technology.

“Hyperspectral imaging technology supersedes the point-to-point scanners previously used, and due to its finer resolution, covers 256 spectrum measuring points rather than the usual 16,” he says.

“This allows our machines to evaluate even the slightest differences in material chemical composition.”

Prior to STEINERT’s UniSort BlackEye, Johann says operators had two choices: density separation or separation based on electrostatic properties.

“Both of these mechanisms had their limitations. For instance, density separation cannot distinguish between polyethylene and polypropylene, while electrostatic separation only works with dry and very homogenous material,” he says.

The UniSort BlackEye is capable of separating light and dark polymers between 10- and 44-millimetre fractions. It also features a feed and dispensing device with a material hopper, acceleration conveyor belt, containment hood and compressed air nozzle bar.

STEINERT’s UniSort Film, Johann adds, is suited for low-weight film, paper and other 2D fractions.

“The separation process is very demanding when it comes to light 2D components, many of which have the added issue of black pigment,” Johann says.

One of the challenges is that to achieve optimal sorting, material needs to remain in a stable position on the sorting belt. As a result, operators are often forced to slow belts down, making sorting uneconomical.

“The UniSort Film design circumnavigates this issue through an elaborate ventilation system that allows effective acceleration on a high-speed belt, with speeds up to 4.5 metres a second,” Johann says.

“The machine’s targeted airflow is synchronised across the entire belt, meaning both the belt and air surrounding the material travels at the same speed. This enables a roughly 50 per cent higher throughput when compared to standard system designs.”

Johann says STEINERT’s philosophy is simple: using future-focused technologies to solve the problems of today.

“We believe in developing technologies that allow our customers to generate added value in their field of work. And, as part of that commitment, aim to provide innovative solutions to the waste problems plaguing us right now, while always keeping our eye on what’s around the corner,” he says.

Pictured: Shannon Bricknell (left) and Johann Hefner (right), at the UniSort Black demonstration machine in Melbourne.

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