This work investigates an innovative process to valorise agricultural digestate by the exploitation of solar energy. Digestate has been located in a lab-scale greenhouse to evaporate the liquid phase. Digestate vapours, rich in ammonia, are sent in a Drechsler trap, filled with 38% w/w sulfuric acid solution, through three solar air fans. A concentration of about 2 M of ammonium sulphate solution was recovered. The remaining dried solid phase, rich in phosphorous compounds, was evaluated as alternative to the commercial fertilizers (46% P2O5) in the growth of maize plants. Equal amount of P was applied to each pot (25 mg/kg soil). The plants were evaluated along the 8 weeks in a greenhouse monitoring the growth parameters and leaf SPAD index, micro-, macronutrients and non-essential heavy metals. The results evidenced that the dried solid phase of digestate can be used as an alternative source of P. Graphic Abstract