With the help of bales of silage, farmers produce long-life feed for cattle and other farm animals. The problem: So far, the plastic films used for this have mostly been made from crude oil, disposed of after use and also leave microplastics in the soil. Scientists are therefore now researching a biodegradable silage film made from renewable raw materials that is just as stable and durable.
Farmers store green fodder such as grass, clover or peas in order to produce long-lasting feed for their livestock for the winter. To do this, the cut plants are hermetically sealed in silos or round bales so that they ferment and lactic acid is formed, which makes the feed durable. Due to the increasing demand for feed, this so-called silage production in German agriculture has increased significantly in the last few decades. As a consequence, more and more packaging films are required, which up to now have been conventionally produced from crude oil and which leave microplastics in the soil. After their use, the foils are usually thrown away immediately, which makes them an environmentally harmful single-use product.
Is that also possible in an environmentally friendly way?
Researchers around Michael Nase from the Hof University of Applied Sciences have now asked whether this is also more sustainable. As part of a feasibility study, they want to investigate by April 2022 to what extent and under what conditions conventional silage films can be replaced by environmentally sustainable films made from biopolymers. “Our goal is that the foils will consist of 100 percent renewable raw materials in the future,” says Nase’s colleague Isabell Kleiber. “We would like to develop them from a disposable item to a product that is compostable or recyclable and can therefore be perfectly integrated into the agricultural production cycle.”
To this end, the scientists are experimenting with different biopolymers and their composition. Using a special device, the scientists prefer to mix so-called polyactides (PLA) and polybutylene adipate terephthalate (PBAT) – two plastics that can be produced on the basis of renewable raw materials such as sugar. The materials are biodegradable and compostable and could therefore, as “bio-plastics”, be a more environmentally friendly alternative to plastic films.
Bio-based, but still stable
The challenge here: The researchers are not only looking for possible alternative raw materials, but also want to make the film as durable and stable as possible. “First and foremost, the film has to demonstrate a 400 percent elongation at break,” explains Kleiber. “That means that you have to be able to stretch it very much without it tearing. In addition, it has to be very UV-resistant, as it will usually be left outside for a whole year. ”They are also working on making the alternative film impermeable to water and oxygen so that the fermentation process in the silage works. The first investigations so far have shown that a three-layer film could meet these properties, with each layer covering a different requirement, according to the research team.
“Our job is that the ecological film must have even better properties than the conventional film – because ultimately it will also cost a little more,” explains Kleiber. Bio-plastics have so far cost four to six euros more per kilo, which will make bio-based films correspondingly expensive. The product is now being tested and optimized in the ongoing work. From 2022, Nase and his colleagues finally want to deal with the technical feasibility of the ecological agricultural stretch film.
Source: Hof University of Applied Sciences