Phosphorus flow from large-scale fertilizer and feed additive chemical enterprises

Phosphorus (P), as an essential nutrient for crops and livestock, is a non-renewable resource. In order to improve the productivity of agriculture and animal husbandry, about 80% of phosphate rocks are used to produce phosphate fertilizers and P feed additives. Therefore, it is very important to improve the production efficiency of P. However, information on flow characteristics and use efficiency of P in the production chain of "mining-benefaction-phosphoric acid-P fertilizers (feed additive)" has remained scarce. This study was done in support of establishing database on P flow through enterprise survey. The fertilizer and feed additive production module of NUFER (NUtrient flows in Food chains, Environment and Resources use) model, which is based on Material Flow Analysis (MFA) was used. Using a large P chemical enterprise in China as a case study, we analyzed P flow characteristics, P use efficiency, P footprint and P loss in the "mining-benefaction-phosphoric acid-P fertilizers (feed additive)" system and future scenarios for P chemical enterprises. The results showed that of the 3 902 Gg P ore resources (100% P₂O₅, the same as below), only 2 426 Gg ended up in fertilizers and P feed additives in 2015. Diammonium phosphate (DAP) was the highest yield product (1 558 Gg), followed by mono-ammonium phosphate (MAP), NPK compound fertilizer (NPK), triple superphosphate (TSP), di-calcium phosphate (MDCP) feed additive, single superphosphate (SSP), NPS compound fertilizer (NPS) and potassium dihydrogen phosphate (KH₂PO₅). The corresponding yields were respectively 634 Gg, 154 Gg, 130 Gg, 34 Gg, 22 Gg, 3 Gg and 1 Gg. The production efficiency was 99% for NPK, 98% for DAP, MAP and NPS, 95% for MDCP, 93% for TSP and 91% for SSP and KH₂PO₅. The production efficiency of the entire production chain was 80%. Most of the P loss came from phosphate rock processing, which accounted for 51% of total P loss. This was followed by mining (25%) and phosphoric acid product (14%). By optimizing production efficiency and improving recycling rate of wastes, P loss was expected to reduce by 42%. Although the utilization efficiency of P in the enterprise was at an advanced stage in China, there was still room for improvement.