Sustainable potting soil from the anaerobic digestion of 100% roadside grass. HoSt has started a pilot with a number of parties to bring this to a success. If the pilot turns out well this year, it is expected that after 2022 a grass digester will be realised. This plant can produce 15,000 m3 of potting soil and 1.5 million Nm3 of biomethane per year.

At an existing biogas plant, supplied by HoSt in the Frisian Jelsum, a small-scale test digester has been set up for tests. The process consists of chopping roadside grass, cleaning the roadside grass and then the anaerobic digestion. The product that is created after digestion is called digestate, which is separated into a thin and thick fraction. The thick fraction is processed into a valuable product that is comparable in composition and structure to peat.

Cooperation between the Dutch regions Friesland, Twente & Achterhoek

The pilot is being carried out by HoSt (Enschede) in collaboration with D4 (Leeuwarden). At the same time, ‘Groot Zevert Vergisting’ (Beltrum) and the Biomass Foundation (Aalten) are also conducting tests as part of the ‘Achterhoekse regio Deal Kringlooplandbouw’ (Achterhoek Region Deal Circular Agriculture) and is financially supported by the Province of Gelderland and the region Achterhoek. Wageningen University & Research analyses the end products of both tests and examines the seed germination and the growth of plants.

Circular potting soil

The potting soil as we know it now mainly consists of peat, due to its high carbon content, and also contains added nutrients. Peat is a non-sustainable and non-circular raw material. Nature areas in, among others, the Baltic States and Finland are being excavated to extract peat. The use of peat is therefore not circular and is associated with greenhouse gas emissions of CO2 and CH4. Annually, 4 million m3 of potting soil is used in the Netherlands and potting soil with peat may (still) be sold in the Netherlands. In Great Britain, only potting soil without peat is allowed for sale. This Dutch pilot is a step in the direction of this sustainability transition.