Integration of biochar in psychrophilic anaerobic digestion: effect on the digestate

This study evaluated the effect of biochar on the quality and fertilizer potential of the digestate produced during psychrophilic anaerobic co-digestion (ACoD). Two digestates were considered from the cheese whey and cattle manure treatment: T1 (Control) from a reactor without biochar and T2 from a biochar-supplemented reactor. First, the samples were characterized by organic matter, nutrients, and pathogens content. Subsequently, the digestates fertilizer potential was evaluated in a lettuce crop. The results showed that biochar supplementation allows the obtainment of a more stable digestate with 30% more nitrogen content than the control digestate. In both digestates, the presence of pathogenic microorganisms was not detected. T2 has a positive effect on lettuce vegetable development, comparable with Urea's, and reduces N-nutrient leaching compared to T1 when applied to the soil. The results revealed that biochar integration into ACoD produced a digestate that can replace inorganic fertilizers in short-cycle horticultural crops such as lettuce.