The work aims to examine and discuss the fertilizing properties of digestate (digested pulp) from three different agricultural biogas plants in terms of the substrates used. Based on the market prices of fertilizers, the economic value of the digestate has been assessed. For a selected biogas plant, the economic balance has been calculated, taking into account the income resulting from the sale of the digestate. The results obtained allow for stating that samples of digestate were rich in nitrogen (up to 6.58 g kg−1), and potassium (up to 16.3 g kg−1) in fresh matter (FM). The value of the digestate for installations was estimated in the range of 6.08–15.36 EUR·Mg−1. The analysis for one of the 1 MW biogas plants shows that under current conditions of supporting systems, the daily income for a biogas plant is 1,414 EUR and the digestate produced is worth another 334.4 EUR. Its application, especially on fields adjacent to biogas plants, is part of the principle of nutrient recovery in the circular economy.