New alternatives: agro-based and bio-based materials

Sustainable alternatives to conventional packaging materials have been widely discussed in recent months. If plastics are based on alter­native, organic raw materials, such as plant products or biomass, this makes it possible to transition away from petrochemically derived plastics almost entirely. In this context, the term “biopolymer” covers the raw material (biomass or petroleum) from which a plastic is formed as well as its compostability.

There are now many plastics capable of meeting either just one or both of these criteria. The raw materials are classified into different generations. First-generation raw materials are primary crops such as kernels of corn from industrial corn cultivation. A second-gene­ration raw material describes a secondary crop component, such as leaves or stems. Lastly, the category of third-generation raw materials covers organic waste from a vast range of sources and quality levels. Despite these materials providing an alternative to petrochemical materials in many applications, they also present signi­ficant challenges. The best example is PLA, a raw material in the first generation of bio-based plastics. Products exclusively made of PLA are only partially heat-resistant, so may deform or leak their contents during either transportation or use. PLA compounds (i.e., mixed plastics) can offer a solution to this problem, but this means reintro­ducing petroleum-based plastics. Another diffi­culty with the use of materials based on organic waste is how to categorize the raw materials. While some materials manufacturers guarantee categories such as kosher or halal, others take the view that 100 percent separation is impos­sible. In addition, nonfossil plastics are, as a rule, more expensive than conventional virgin material.

In recent years, Greiner Packaging has extensively tested agro- and bio-based plastics – finding, for instance, that bio-PET is easy to process. “Generally speaking, we take a somewhat critical view of agricultural land being used to obtain packaging material – that is to say, first-gene­ration material. But waste products from agricul­tural production and general waste (i.e., second-and third-generation material) are interesting to us as prospects for the future that we’re examining in closer detail,” says Stephan Laske, R&D Director at Greiner Packaging.

Many companies are currently turning to the mass balance approach when it comes to alternative materials. As with the green electricity model, this approach involves replacing fossil-based resources with sustainable (recycled or agro-based) feedstock right at the start of the production process. The proportion of renewable resources fed in is allocated to the new product. This process is certified by an independent institution.