The use of digestates and recovered ammonium sulfate from NH3-scrubbing as sustainable substitutes for chemical fertilizers: a field-scale assessment

Nutrient recovery from bio-waste as renewable fertilizers with high nutrient use efficiency (NUE) has gained increased attention in order to meet both regulatory drivers (increasingly stringent fertilization and discharge levels) and market demands, while producing an internal revenue source, hence turning the waste problem into an economic opportunity. The aim of this study was to validate the agronomic effectiveness of fertilization strategies using bio-digestion waste derivatives as compared to conventional practices using animal manure and chemical fertilizers. In a two-year field trial, NUE’s and nutrient balances were assessed for N, P, K, S, Ca, Mg and Na. An economic and ecological evaluation was also conducted. Complete substitution of chemical fertilizer N by wastewater from NH3-scrubbing resulted in higher N and P use efficiencies, whereas the use of digestate mixtures resulted in significantly higher K and P use efficiencies. Small increases in crop yield were obtained when the liquid fraction of digestate was used as NK-fertilizer in addition to animal manure. As added benefits to the generation of bio-fertilizers from waste, renewable energy is produced, and the economic and ecological impact of plant production is significantly reduced. Moreover, an additional supply of organic carbon, Ca, Mg and S is delivered