Nutrient recovery from biodigestion waste (water) streams and reuse as renewable fertilizers: a two-year field experiment

The aim of this study was to evaluate the impact of using bio-digestion waste derivatives as substitute for synthetic fertilizers and/or as P-poor equivalent for animal manure on soil and crop production. In a field trial, nutrient balances were assessed and the physicochemical soil fertility and quality were evaluated. The biogas yield of the harvested energy crops was also determined. An economical and ecological evaluation was conducted. The highest biomass yields were obtained when the liquid fraction of digestate was used as P-poor fertilizer in addition to animal manure. Furthermore, the complete substitution of synthetic fertilizer N by air scrubber waste water resulted in the highest N and P use efficiencies. Finally, for all reuse scenarios the calculated economical and ecological benefits were significantly higher as compared to the common practice using animal manure and synthetic fertilizers