The solid digestate from high solid anaerobic digestion was used as growth medium for seeding production. The garage-type dry fermentation system using bundled rice straw and swine manure was performed to obtain solid digestate. The addition of solid digestate addition greatly influenced the properties of the growth medium. The bulk density increased and the total porosity, pH, and electrical conductivity (EC) values were decreased with the reduction of solid digestate. The solid digestate-based media had a bulk density < 0.3 g/cm3, total porosity > 70%, air filled porosity ~ 3%, water holding porosity > 60%, EC < 3 mS/cm, and 6.5 < pH < 8. Those properties almost satisfied the essential requirements of nursery substrate. Also, the concentrations of nutrients and heavy metals of the substrate exhibited a positive relationship with solid digestate addition, and they are all within acceptable ranges for plant growth. When the addition of solid digestate was 50% (v/v), the germination rate of tomato seeding cultivated in that solid digestate-based growth medium reached 85%. These findings showed that the solid digestate from the high solid anaerobic digestion could be successfully applied in the seeding nursery and merit consideration for industrial applications.
Enhanced enzymatic conversion with freeze pretreatment of rice straw
