LAUSR

Abstract In recent years, the amount of biosolids used for land application has increased constantly. Many studies detail the interest of recycling biosolids in agriculture. However, there is a need for a consumer-oriented model that can predict P-efficiency of biosolids regardless of their origin and composition. Literature about the P availability from a wide variety of biosolids was gathered, in tabular or graphical forms, in order to build two models. Model I, with a set of 93 data points, describes the apparent P-recovery (APR in %), and Model II, with 121 data points, describes the relative P effectiveness (RPE in %). Both models are related to total [Al+Fe] in mmol kg −1 . Model I is rational function (1:1), i.e. APR = [− 3.86[Al+Fe] total  + 12530]/[[Al+Fe] total − 87.85], with an R 2 of 0.92. The models shows rapid decrease in biosolids P efficiency with increasing [Al+Fe] total . These models make possible predictions of relatively high accuracy. Model I was used to develop a classification of biosolids with respect to their P bioavailability, while Model II can help predict the amount of any particular biosolids required to meet an equivalent P mineral fertilization level. Graphical Abstract