Case Story Germany

BIOWERT GRASS BIOREFINERY

BIOBASED PLASTICS, GERMANY

June 2019

PLANT CONCEPT AND FRAMEWORK CONDITIONS

We live in a world with significant concerns related to climate change and an associated need to reduce significantly use of fossil resources; this necessitates supply of energy and products from renewable sustainable resources. The principle of biorefineries is resource-efficient utilisation of bio-based raw materials. Based on this concept, the Biowert Industrie GmbH was founded by Michael Gass in 2000 as a Swiss-German company. The first Biowert grass refinery started operation in 2007 and is located in Brensbach, Germany, on an 18,000 m2 site (Figure 1).

The main products based on grass from permanent pastureland and arable land for crop production are grass fibre insulation (AgriCellBW), natural fibre reinforced plastic (AgriPlastBW, Figure 2) and fertiliser made from digestate (AgriFerBW). The facility has an annual throughput of about 2,000 t dry matter (equivalent to 8,000 t grass per year at 25%–30% dry matter content). The integrated biogas plant produces c. 1,340,000 m3 of biogas annually which is used in combined heat and power facilities, which in 2012 produced 5.2 GWhel of electricity.

The Biowert cycle is shown in Figure 3. Grass is stored within bunker silos, where the ensiling process takes place. The first step after ensiling includes mechanical treatment of grass silage and isolation of grass fibres through pulping, drying and pressing processes. The grass fibres are further processed into AgriCellBW and AgriPlastBW synthetic granules. AgriPlastBM contains 30 – 50% grass fibres and 50–70% recycled polyolefine and is used for injection moulding for a range of uses (Figure 2).

The grass juice remaining from mechanical pretreatment of grass silage is used as substrate in the biogas plant (together with local co-substrates such as food waste and slurry). The heat and electricity derived from the biogas facility is used to satisfy the energy in the biorefinery and excess electricity is exported to the electricity grid. Wastewater arising from the process is reused for pretreatment (slurrying) of grass silage. Digestate from the biogas plant is further processed to a concentrated and a liquid biofertilizer (AgriFerBW) used by local farmers. This closes the nutrient cycle in the circular economy.