Post-fermentation pulp, which is the by-product of biogas production, can be used inter alia for fertilisation purposes in agriculture [1][2][3][4][5][6]. However, the fertilisation characteristics of the digestate vary. They depend on the substrates used, which may be as follows: plant biomass, waste from the agri-food industry or natural fertilisers [2].According to legal regulations, a given digestate can be directly regarded as a fertiliser, a soil conditioner, or one of the raw materials to produce a fertiliser or plant conditioner [6,7]. The best plant substrates used for biogas production are sugar beet, maize [8,9], sorghum [10], and other grasses and cereals [11]. In addition, there are reports of other alternative