Dairy processing sludge and co-products: A review of present and future re-use pathways in agriculture

The dairy industry is one of the largest global producers wastewater and generates huge volumes processing sludge (DPS). There are two main types DPS, lime-treated dissolved air floatation bio-chemically-treated activated sludge. These may also be converted to STRUBIAS (STRUvite, BIochar, AShes) products which have potential as fertilizers, secondary feedstocks for phosphate fertiliser granules, soil amendments. A small number studies indicate that these variable nutrient metal contents, differ across product types. This due many factors such type plants, treatment process production technologies. Although land applied, phosphorus (P) nitrogen (N) fertilizer equivalency value (FEV) often unknown not factored into application rates, therefore need study under field conditions (across crop types). review identifies a quantify antimicrobial drugs, hormones, pesticides, disinfectants, persistent organic pollutants (POPs), microplastics nano-particles in all DPS Where detected, testing should follow transfer contaminants soil, water continuum. Further knowledge areas identified would enable both agronomic environmental goals met promote higher uptake re-use agriculture.