Methods for the removal and recovery of nitrogen and phosphorus nutrients from animal waste: A critical review

Livestock and poultry industries are developing rapidly worldwide, responsible for releasing large volumes of manure and liquid waste. The produced manure containing nitrogen (N) and phosphorus (P) nutrients which are causing eutrophication and algal blooms if released into water bodies without prior treatment. Utilization of bio-waste materials for the production of biogas is one of the most useful technologies providing a pollution free environment and a renewable “green” energy. Physical and chemical methods for removal of N and P from animal waste include the application of biochar with different chemical and physical modifications (adsorption), air–cathode single chamber microbial fuel cells (MFCs), an aerobic digested (AD) technique, using ultrasound/H2O2 digestion joined with HFO/biochar adsorption technique, wet scrubber and stripping process, and gas-permeable membrane technology, critically discussed in the manuscript. Future research requirements include integrated approaches and directions regarding the recovery of N and P utilizing organic amendments (like biochar) are discussed.