Looking for the best way to recycle catering waste

Festivals and catering venues have a characteristic waste stream: a high volume of paper (napkins, sugar sachets, placemats, packaging paper, cardboard cups and containers) mixed with an unavoidable plastic fraction consisting of items such as drink bottles, cups and disposable cutlery. This is very similar to a residue fraction Attero already separates before incineration and is searching a technical solution for; paper-plastic residue. On an annual basis, Attero has access to 70,000 tonnes of this type of waste. “We wanted to know whether the paper could be separated via a wet or dry separation process, and if we can meet the quality requirements for recycling,” says senior business developer paper & plastics Olaf Fennis of Attero.

Process recreated at a pilot scale

Attero developed a process in which the waste was sorted by size and turned into wet pulp. After the plastic fraction was separated in a cyclone, the remaining pulp was then cleaned and recycled. Fennis: “Doing something like this in a profitable way requires information on how much new raw materials can be recovered and what the quality of these materials is. As we are not a paper producer, we did not have the knowledge to make these calculations.”

Attero therefore turned to the know-how of Wageningen Food & Biobased Research regarding biorefinery and waste separation processes. Edwin Keijsers was involved in the project as content expert. He recreated the process developed by Attero in the Biobased Products Innovation Plant to test various mixes of paper and plastic, and, eventually, batches of catering waste. For Fennis, the research was an introduction to the world of fibre length, fibre strength, permeability and other properties that determine the quality of paper.

“The great thing about this collaboration is that Wageningen Food & Biobased Research immediately works in accordance with the standards that apply in the sector, while the research is performed in a scientific way: thorough and verifiable. In addition, the organisation is very transparent; we were always welcome to watch and provide input on whether processes tried in the lab could potentially be scaled up in the company later.”

Testing the feasibility of the wet separation process

Keijsers refined the process developed by Attero on various points. “One of the most complex process steps was to separate the paper fibres from plastic particles,” he explains. “Attero had developed a cyclone for this step; a type of centrifuge that casts the plastic to the sides, while the pulp is extracted via a hole in the bottom. Tests showed, however, that the pulp drain was constantly clogged by plastic. The cyclone just wasn’t the ideal solution.”

Following these tests Attero started to doubt the feasibility of the wet separation process. Technically, the company expects the yield to be limited. But there’s good news too: the fibres which can be extracted from catering waste are of a high quality and suitable for recycling.

From sugar-rich residual streams to bioplastics

Attero aims to separate low-quality fibres (from thin packaging paper, for instance) and convert them biochemically into sugars, for fermentation into bioethanol or the production of bioplastics. This step is also being approached in partnership with Wageningen Food & Biobased Research, which has extensive knowledge and experience in extracting pure sugar-rich residual streams and converting them into lactic acid, a major building block for bioplastics.

“I am pleased with our collaboration with Wageningen Food & Biobased Research,” Fennis concludes. “Building our own pilot plant would have been very expensive and it was good to avoid such costs via this preliminary research. In addition, we now know when paper is of good quality and what this requires, allowing us to give our clients the specific details on product quality they need.”