Sustainable all round: natural fibre-reinforced plastic from the grass factory

Grass grows quickly, is uncomplicated and robust - and a strong partner for plastics. Biowert Industrie GmbH proves this by using the renewable raw material to produce a natural fibre-reinforced plastic that is sustainable all round.

In an interview with K-MAG, Jens Meyer zu Drewer talks about how grass is used to produce a reinforcing material for plastics, how the innovative material can be processed and what exactly makes AgriPlast so sustainable.

Mr Meyer zu Drewer, you run a so-called grass factory. What is that all about?

Jens Meyer zu Drewer: We have found that grass is a sustainable material. The cellulose fibre obtained from it can be integrated very well as a filler or reinforcing material in plastics to improve the properties. Furthermore, grass is a fast-growing and robust natural material that can be harvested several times a season, depending on the weather conditions. In our so-called grass factory, we extract the liquid components from the actual cellulose fibre, which is then incorporated into the plastics. Biowert strives for a complete Circular Economy in the production of natural fibre-reinforced plastics, with no effluent or waste.

How is the reinforcing material for plastic made from grass?

Meyer zu Drewer: The process begins with the grass harvest by a producer association of farmers from the region. The freshly cut grass is ensiled in our own grass silo and prepared for further processing. The grass silage is washed with warm water heated by the waste heat from the connected biogas plant or its combined heat and power plant (CHP). The grass fibres are then broken down in a mechanical wet process using a macerator and then separated from the grass juice in three pressing stages. The purified cellulose fibres are dried in a two-stage process at 60°C, resulting in a residual moisture content of 10 %. The drying energy for both the belt and the flight layer dryer again comes from the waste heat of the CHP units. The residual moisture is necessary so that the fibres do not become too brittle and break. The fibres obtained in this way are packaged and can be stored for a long time so that they can later be compounded with recycled plastics to produce the innovative plastic AgriPlast.

The leftovers from grass fibre production are used together with food waste from large kitchens and the food industry in a biogas plant to produce green electricity and heat.  After fermentation of the biomass, a fermentation product remains that is returned to the farmers' association as fertiliser under the name AgriFer.

This creates an almost complete cycle: The plant generates its own energy, the process water is reused, and the composite material AgriPlast can also be recycled several times.

What is the challenge here in particular?

Meyer zu Drewer: Grass fibre is a natural product that is subject to the fluctuations of growth in climatic conditions. In recent years, for example, only two cuts per season were feasible. Although grass is a very robust plant, the yield and quality per hectare can vary. On the one hand, this makes planning for the future quite challenging, especially since we have to forecast demand a year in advance. On the other hand, we have to match production to fibre quality in order to guarantee a consistent quality of the fibres.

For which processing methods is the material suitable? Where is it used specifically?

Meyer zu Drewer: Our natural fibre-reinforced plastic AgriPlast is suitable for both injection moulding and extrusion. Experience has shown that in injection moulding the fibre content is 30-50 %, while in extrusion higher grass fibre amounts of up to 75 % can be processed.

AgriPlast is ideally suited for the injection moulding of various consumer goods, such as clothes hangers, stacking boxes, pens, lipstick tubes, design objects such as furniture handles, or decking boards.

What is the feedback from your customers?

Meyer zu Drewer: We receive very good feedback from the market because with AgriPlast we offer a plastic that immediately saves CO₂ and symbolises the topic of sustainability.

Reference customers are, for example, Cortec GmbH with their clothes hangers made of AgriPlast. In addition, Cortec clothes hangers are used in a large German drugstore chain with its own recycling concept. The hangers remain in the store when the children's textiles are purchased and are reused. The hanging system GRPL made of AgriPlast by the company noThrow design has also been sold on the market for several years. We are seeing increasing demand in the furniture and automotive industries, which are very interested in our product because of its carbon footprint.

What contribution do you make to climate protection at Biowert?

Meyer zu Drewer: Our solution is to replace up to 75 % of petroleum-based plastics with cellulose from grass. In addition, new fossil raw materials are avoided in AgriPlast production through the use of recycled plastics. There is also less resource consumption due to our own electricity and heat production from residual materials. By using AgriPlast with a fibre content of 40%, our customers can save a good 64% CO₂.

In addition, the grass we use for production is grown by farmers in the neighbourhood - on land that would otherwise be unusable. We generate environmentally friendly electricity in excess of our own needs, which we feed into the grid. We return the residues from the plant as fertiliser to our grass suppliers and farmers. In this way, we make a sustainable contribution in every respect to the development of rural areas and to the quality of life in the Odenwald in Germany.