Sustainable packaging made from renewable raw materials is on the rise. Can waste products from the food industry also be used as raw materials? Could recycling raw materials be a solution to food waste? Silac wanted to find out and launched a research project in collaboration with ZHAW Life Sciences and Facility Management. The results are promising.

2.8 million metric tons of food waste

According to a study by the Federal Office for the Environment, over 2.8 million metric tons of food waste are generated in Switzerland. This consists of food that was produced for human consumption but is lost or discarded on its way from the field to the plate. Food processing accounts for the largest share, at 35 percent. Food waste occurs here when not all byproducts are used (for example, whey, okara from tofu production, and offal).

Although some food waste is used in the animal feed industry or recycled through thermal processing, the vast majority is simply disposed of. This cannot be allowed to continue, because food waste has far-reaching effects on our environment and our climate.

We now know that it is too expensive to try to salvage food at the end of the food chain. Therefore, efforts are focused in the opposite direction: on developing new processing methods and product innovations with the goal of achieving a circular economy. The goal is to reduce unused raw materials, upcycle byproducts and food waste, and reintroduce them into the food chain. In late 2021, the first cross-industry trading platform for industrial byproducts, called Circado, was launched by the Zurich-based company RethinkResource. The platform brings suppliers and buyers together and has already facilitated numerous innovative partnerships and produced forward-looking end products. Examples include body scrubs made from fruit pits, chips made from spent grain, and yarn made from orange peels. There are countless possibilities for a circular economy.

 

Packaging Made from Byproducts

Interest in sustainable raw materials is also high at Silac. On the one hand, sustainability has always been a priority for this family-owned company; on the other hand, demand for bio-based, plastic-free packaging has risen sharply in recent years. Silac has already gained initial experience with renewable bioplastics through the successful launch of the cellulose-plastic cap for SIGG Switzerland. Now, the innovative plastics manufacturer wants to take it a step further and utilize sustainable raw materials derived from food industry waste. These so-called by-products are to be used as an alternative to plastic in packaging and make an important contribution to reducing food waste. To this end, Silac, together with the ZHAW Institute for Food and Beverage Innovation and Sax Polymers Industrie AG (hereinafter SAX), launched the research project “Packaging from By-Products.”

The purpose of this preliminary study was to assess the feasibility of using by-products from food production to manufacture injection-molded or hot-pressed parts. The project examined the following aspects:

• What types of waste products from the food industry would be suitable?
• What compounding process should be used (addition of additives)?
• What results can be achieved using the injection molding process?

 

Evaluation of Potential By-Flows

The ZHAW Institute for Food and Beverage Innovation searched the technical literature for suitable raw materials from various by-product streams. The raw materials were to come from Switzerland, be available year-round, and be obtainable in the necessary quantities. Furthermore, their composition and processability as bioplastics played an important role.

Based on the above criteria, the following four raw materials were selected:

• Potato peels, volume 26,127 metric tons of dry matter per year
• Whey protein, volume: 15,184 metric tons of dry matter per year
• Gluten, a byproduct of starch production
• Coffee grounds, volume 6.5 metric tons of dry matter per year

Gluten was ultimately removed from the list due to its allergenic potential.

 

The Right Recipe

In a second step, the research team evaluated possible formulations for compounding. This is a specialized process in plastics manufacturing in which additives are mixed in to achieve the desired properties. These properties may include, among others, a specific color, a higher flash point (the composite material does not ignite until it reaches significantly higher temperatures), or improved mechanical properties such as tensile strength, impact resistance, or elongation at break.

In its research, the research group also investigated which bioplastic is best suited for incorporating by-products. The choice fell on the polyester polybutylene succinate, or PBS for short, since the team already had some expertise in processing this material. To ensure machinability, a 70/30 PBS/by-product ratio was to be used in an initial practical trial.

 

Successful Extrusion

SAX was responsible for the initial pilot tests. The Swiss company specializes in the production, processing, and coloring of engineering plastics. Before the actual compounding process, SAX employees first had to pretreat the selected by-products. Coffee grounds and potato peels were first dried, then ground, and dried again. The whey protein concentrate simply had to be dried until it was ready for use.

The by-products could now be compounded with the PBS bioplastic. The extrusion process (a shaping process) was successful for all three raw materials used. The end result: sustainable pellets ready for further use.

 

Promising Feasibility Study

In the second step, shoulder and impact bars were injection-molded from these by-product compounds to determine their mechanical and physical properties.

And last but not least, Silac employees tested the processability of the compounded pellets using injection molding. For this purpose, the project team selected a “challenging” three-dimensional mold in the shape of a globe stand. The goal was to determine whether the developed pellets would meet the high stability and performance requirements.

Through process optimization, the injection molding parameters for the respective side-stream compounds were adjusted so that all three side streams could be processed into the three-dimensional part.

Raw Materials from the Circular Economy

The preliminary study has shown that a material suitable for mass production can be developed from the three food by-product streams. Even though further development and optimization are still needed, the potential is clearly there. What’s next?

We are confident that our customers are open to this sustainable approach and that we will soon be able to produce packaging made from food waste on a large scale. After all, the benefits of the circular economy are clear. We all benefit from recycling raw materials.

Would you like to do your part to reduce food waste? Get in touch with us today.