This study aimed to improve the phosphorus (P) use efficiency of various biowastes. To achieve this, we proposed the combination of placement and the acidification of biowastes for the development of P-efficient biobased fertilizers. Seven biowastes were used as P-fertilizers, including two meat and bone meals (MBM), two solid fractions of biogas digestate (BGF), and three sewage sludges (SS). Two acidification approaches were evaluated: pre-treatment with sulfuric acid (73.5 g sulfuric acid per kg fresh weight) and co-application with ammonium sulfate (15 mg N per kg soil). The treated materials were placed close to winter wheat (Triticum aestivum cv. Benchmark) seeds in a 42-day pot experiment in a growth chamber. The P use efficiency was compared to the corresponding untreated material homogeneously mixed or similarly placed in the soil. A ³³P indirect labeling method was used to differentiate P uptake from soil and fertilizer. The negative control showed a shoot dry matter of 0.42 g ( ± 0.05) and a total P uptake of 0.62 ( ± 0.06) mg per plant. The placement of acidified sewage sludge did not show significant differences in shoot dry matter and P uptake compared to the negative control. On the other hand, the placement of acidified MBM significantly increased plant growth (MBM I: 2.93 ± 0.46; MBM II: 1.78 ± 0.09 g) and P uptake (MBM I: 7.38 ± 1.10; MBM II: 6.21 ± 0.53 mg) compared to the untreated MBM placed and the negative control. Similarly, the placement of acidified BGF showed promising results, with a 3-fold increase in P uptake from the fertilizer compared to untreated BGF mixed with the soil (7.74 ± 1.47 vs. 2.71 ± 0.26 mg). Therefore, our results demonstrate that the placement of acidified MBM and BGF can increase the P use efficiency of these biowastes and may provide a basis for formulating P-efficient biobased fertilizers using these materials.