Two laboratory incubation studies and a growth room bioassay of forage barley were conducted to investigate nitrogen (N) and phosphorus (P) mineralization, and nitrous oxide emission from two contrasting agricultural soils amended with anaerobically digested cattle manure (ADM). The ADM is a nutrient-rich co-product from manure-based biogas plants which is applied to cropland at rates used for raw manure since scientific information on nutrient release from ADM is lacking. Application of the separated solids fraction of ADM (SS) reduced nitrous oxide emission but resulted in lower N mineralization compared to raw manure in both soils. Raw manure- and SS- treatments had similar biomass yields and P supply capacities while the application of pelletized SS (PSS) caused net N immobilization, lower P release than manure and SS, and depressed barley yields relative to non-amended (control) soils.

Two laboratory incubation studies and a growth room bioassay of forage barley were conducted to investigate nitrogen (N) and phosphorus (P) mineralization, and nitrous oxide emission from two contrasting agricultural soils amended with anaerobically digested cattle manure (ADM). The ADM is a nutrient-rich co-product from manure-based biogas plants which is applied to cropland at rates used for raw manure since scientific information on nutrient release from ADM is lacking. Application of the separated solids fraction of ADM (SS) reduced nitrous oxide emission but resulted in lower N mineralization compared to raw manure in both soils. Raw manure- and SS- treatments had similar biomass yields and P supply capacities while the application of pelletized SS (PSS) caused net N immobilization, lower P release than manure and SS, and depressed barley yields relative to non-amended (control) soils.

Bioelectrochemical systems (BES) is a platform technology that is able to realize versatile engineering functions and recover valuable resources in an energy-efficient manner. One of the potential applications of BES is to remove and recover nutrients simultaneously from nutrient-rich wastewater, such as digested manure from livestock. A four-chamber BES was developed and used in this study to explore the potential to remove and recover hexavalent Chromium from synthetic wastewater, and ammonia and phosphate from digested manure. The BES was able to achieve 99.6% removal of Chromium by membrane adsorption in 5 days but failed to recover in the concentration chamber. Nutrients were removed from the waste stream and recovered in the recirculated catholyte by the electrical field generated from the waste. The BES was demonstrated to achieve substantial COD removal, nutrients removal and recovery. On average, the removal efficiencies were about 50% for COD, 85% for NH4-N and 40% for PO4-P, and the concentration of NH4-N recovered in the catholyte was 670 mg/L after 5 cycles under an applied voltage of 0.8 V. PO4-P was not recovered in solution, probably because it has precipitated under the alkaline condition together with Mg2+ and Ca2+ concentrated in the catholyte. It was also demonstrated that nutrients removal and recovery depended on the current generation and were mostly completed at high current. To sum up, the BES was proven to be an effective and sustainable approach to remove and recover nutrients from digested manure. / Master of Science